eZ80F91 MCU Product Specification

eZ80F91 MCU Product Specification
An
Company
eZ80Acclaim!® Flash Microcontrollers
eZ80F91 MCU
Product Specification
PS019215-0910
Copyright ©2010 by Zilog®, Inc. All rights reserved.
www.zilog.com
Warning:
DO NOT USE IN LIFE SUPPORT
LIFE SUPPORT POLICY
ZILOG'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE
SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF
THE PRESIDENT AND GENERAL COUNSEL OF ZILOG CORPORATION.
As used herein
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b)
support or sustain life and whose failure to perform when properly used in accordance with instructions for
use provided in the labeling can be reasonably expected to result in a significant injury to the user. A
critical component is any component in a life support device or system whose failure to perform can be
reasonably expected to cause the failure of the life support device or system or to affect its safety or
effectiveness.
Document Disclaimer
©2010 by Zilog, Inc. All rights reserved. Information in this publication concerning the devices,
applications, or technology described is intended to suggest possible uses and may be superseded. ZILOG,
INC. DOES NOT ASSUME LIABILITY FOR OR PROVIDE A REPRESENTATION OF ACCURACY
OF THE INFORMATION, DEVICES, OR TECHNOLOGY DESCRIBED IN THIS DOCUMENT.
Z I L O G A L S O D O E S N O T A S S U M E L I A B I L I T Y F O R I N T E L L E C T U A L P R O P E RT Y
INFRINGEMENT RELATED IN ANY MANNER TO USE OF INFORMATION, DEVICES, OR
TECHNOLOGY DESCRIBED HEREIN OR OTHERWISE. The information contained within this
document has been verified according to the general principles of electrical and mechanical engineering.
eZ80, Z80, and eZ80Acclaim! are registered trademarks of Zilog, Inc. All other product or service names
are the property of their respective owners.
PS019215-0910
eZ80F91 MCU
Product Specification
iii
Revision History
Each instance in the Revision History reflects a change to this document from its previous
revision. For more details, refer to the corresponding pages or appropriate links given in
the table below.
Date
Revision
Level
Section
Description
Page
Number
September 15
2010
All
Updated logos and copyright date.
All
August
2008
14
Ordering Information
Updated Part Number Description
section.
360
May 2008
13
Introduction, Figure 48, ZDI- Replaced ZPAK II with USB Smart
Supported Protocol, and
Cable
Figure 49
231, 232,
and 233
September 12
2007
General-Purpose Input/
Output, Flash Memory,
Universal Asynchronous
Receiver/Transmitter, Serial
Peripheral Interface, RealTime Clock Control Register,
I2C Serial I/O Interface, Pin
Description, and Ordering
Information.
4, 53,
112,174,
176, 201,
223, and 359
February
2007
Register Map, GPIO Mode 7—Alternate Functions, Register Map - 27, 45, 54,
Table 3. Low-Power Modes, Electrical Characteristics chapters.
339
Updated Table 93.
11
PS019215-0910
Updated Table 1, Figure 6, Flash
Program Control Register, UART
Transmitter, Figure 40, Table 93, I2C
Registers and Ordering Information.
Revision History
eZ80F91 MCU
Product Specification
iv
Date
Revision
Level
Section
June 2006 10
PS019215-0910
Description
Page
Number
Global modifications
Updated for new release.
All
Pin Identification on the
eZ80F91 Device
Table 3: The description of the
following pins modified: pins 55, 61,
63 and 69
6
General-Purpose Input/
Output
GPIO chapter totally rewritten
49
Chip Selects and Wait
States
Input/Output chip select operation
modified
65
Flash Memory
The following sections are modified in 97
Flash memory chapter: Erasing Flash
memory, Information page
characteristics, Flash Write/Erase
protection register, Flash program
control registers, and Table 43.
Real-Time Clock Overview
Added a note in real time clock
overview section
159
Universal Asynchronous
Receiver/Transmitter
Table 102 and 109 modified
175
Infrared Encoder/Decoder
Control Registers
The field [7:4] modified in Table 111
199
Zilog Debug Interface
Updated the Introduction section,
Added two paragraphs to ZDI Read
Memory Registers
231
On-Chip Oscillators
336
On page 349, Figure 63
Recommended Crystal Oscillator
Configuration, the value of inductance
L is changed to 3.3 H
On page 351, Table 232, changed
serial resistance value from 40 k to
50 k
POR and VBO Electrical
Characteristics
In Table 235: Min, Typ, and Max
values of VBO voltage threshold
modified and added ISpor_vbo
parameter
341
Ordering Information
Ordering information modified
359
Revision History
eZ80F91 MCU
Product Specification
v
Table of Contents
Architectural Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
System Clock Source Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
eZ80® CPU Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
New Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
External Reset Input and Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Voltage Brownout Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
SLEEP Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
HALT Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Clock Peripheral Power-Down Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
General-Purpose Input/Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
GPIO Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
GPIO Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
GPIO Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Interrupt Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Maskable Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
GPIO Port Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Chip Selects and Wait States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Memory and I/O Chip Selects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Memory Chip Select Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Input/Output Chip Select Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Wait States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
WAIT Input Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Chip Selects During Bus Request/Bus Acknowledge Cycles . . . . . . . . . . . . . . . 70
PS019215-0910
Table of Contents
eZ80F91 MCU
Product Specification
vi
Bus Mode Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
eZ80® Bus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Z80® Bus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Intel Bus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Motorola Bus Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Chip Select Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Bus Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Random Access Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
RAM Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Flash Memory Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Reading Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Memory Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Programming Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Erasing Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Information Page Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Flash Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Watchdog Timer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Watchdog Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Programmable Reload Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Basic Timer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Specialty Timer Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Timer Port Pin Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Multi-PWM Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
PWM Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Modification of Edge Transition Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
AND/OR Gating of the PWM Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
PWM Nonoverlapping Output Pair Delays . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Multi-PWM Power-Trip Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Multi-PWM Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Real-Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Real-Time Clock Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
PS019215-0910
Table of Contents
eZ80F91 MCU
Product Specification
vii
Real-Time Clock Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Real-Time Clock Oscillator and Source Selection . . . . . . . . . . . . . . . . . . . . . . . 160
Real-Time Clock Battery Backup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Real-Time Clock Recommended Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Real-Time Clock Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Universal Asynchronous Receiver/Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . 175
UART Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
UART Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
UART Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
UART Recommended Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Baud Rate Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
BRG Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
UART Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Infrared Encoder/Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Transmit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Receive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Infrared Encoder/Decoder Signal Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Loopback Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Serial Peripheral Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
SPI Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
SPI Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
SPI Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
SPI Baud Rate Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Data Transfer Procedure with SPI Configured as a Master . . . . . . . . . . . . . . . 205
Data Transfer Procedure with SPI Configured as a Slave . . . . . . . . . . . . . . . . 206
SPI Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
I2C Serial I/O Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
I2C General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
Transferring Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Clock Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
I2C Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
PS019215-0910
Table of Contents
eZ80F91 MCU
Product Specification
viii
Zilog Debug Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
ZDI-Supported Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
ZDI Clock and Data Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
ZDI Start Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
ZDI Register Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
ZDI Write Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
ZDI Read Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
Operation of the eZ80F91 Device during ZDI Break Points . . . . . . . . . . . . . . . 238
Bus Requests During ZDI Debug Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
ZDI Write Only Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
ZDI Read Only Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
ZDI Register Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
On-Chip Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Introduction to On-Chip Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
OCI Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
OCI Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
JTAG Boundary Scan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Phase-Locked Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
PLL Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
Power Requirement to the Phase-Locked Loop Function . . . . . . . . . . . . . . . . . 268
PLL Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
PLL Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
eZ80® CPU Instruction Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
Ethernet Media Access Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
EMAC Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
EMAC Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
EMAC Shared Memory Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
EMAC and the System Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
EMAC Operation in HALT Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
EMAC Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
EMAC Interpacket Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
PS019215-0910
Table of Contents
eZ80F91 MCU
Product Specification
ix
On-Chip Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
Primary Crystal Oscillator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
32 kHz Real-Time Clock Crystal Oscillator Operation . . . . . . . . . . . . . . . . . . . 337
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
DC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
POR and VBO Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Flash Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
Current Consumption Under Various Operating Conditions . . . . . . . . . . . . . . . 341
AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
External Memory Read Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
External Memory Write Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
External I/O Read Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
External I/O Write Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
Wait State Timing for Read Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
Wait State Timing for Write Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
General-Purpose Input/Output Port Input Sample Timing . . . . . . . . . . . . . . . . . 354
General-Purpose I/O Port Output Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
External Bus Acknowledge Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
Part Number Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Customer Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
PS019215-0910
Table of Contents
eZ80F91 MCU
Product Specification
1
Architectural Overview
Zilog’s eZ80F91 device is a member of Zilog’s family of eZ80Acclaim!® Flash microcontrollers. The eZ80F91 is a high-speed microcontroller with a maximum clock speed
of 50 MHz and single-cycle instruction fetch. It operates in Z80®-compatible addressing mode (64 KB) or full 24-bit addressing mode (16 MB). The rich peripheral set of the
eZ80F91 makes it suitable for a variety of applications, including industrial control,
embedded communication, and point-of-sale terminals.
Features
Key features of eZ80F91 device include:
PS019215-0910
•
Single-cycle instruction fetch, high-performance, pipelined eZ80® CPU core 
(referred as The CPU in this document)
•
10/100 BaseT ethernet media access controller with Media-Independent 
Interface (MII)
•
•
•
256 KB Flash memory
•
Two Universal Asynchronous Receiver/Transmitter (UART) with independent Baud
Rate Generators (BRG)
•
•
•
•
Serial Peripheral Interface (SPI) with independent clock rate generator
16 KB SRAM (8 KB user and 8 KB Ethernet)
Low-power features including SLEEP mode, HALT mode, and selective peripheral
power-down control
I2C with independent clock rate generator
IrDA-compliant infrared encoder/decoder
Glueless external peripheral interface with 4 Chip Selects, individual Wait State 
generators, an external WAIT input pin—supports Z80-, Intel-, and Motorola-style
buses
•
•
Fixed-priority vectored interrupts (both internal and external) and interrupt controller
•
•
•
•
Four 16-bit Counter/Timers with prescalers and direct input/output drive
Real-time clock with separate VDD pin for battery backup and selectable on-chip 
32 kHz oscillator or external 50/60 Hz input
Watchdog Timer with internal oscillator clocking option
32 bits of General-Purpose Input/Output (GPIO)
On-Chip Instrumentation (OCI™) and Zilog Debug Interfaces (ZDI)
Architectural Overview
eZ80F91 MCU
Product Specification
2
•
•
•
•
Note:
IEEE 1149.1-compatible JTAG
144-pin LQFP and BGA packages
3.0 V to 3.6 V supply voltage with 5 V tolerant inputs
Operating Temperature Range:
– Standard: 0 ºC to +70 ºC
– Extended: –40 ºC to +105 ºC
All signals with an overline are active Low. For example, the signal DCD1 is active when
it is a logical 0 (Low) state.
The power connections conventions are provided in the table below.
Connection
Circuit
Device
Power
VCC
VDD
Ground
GND
VSS
Block Diagram
Figure 1 on page 3 displays a block diagram of the eZ80F91 microcontroller.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
3
MII Interface
Signals (18)
Ethernet
MAC
RTC_VDD
Arbiter
Real-Time
Clock and
32 KHz
Oscillator
RTC_XIN
RTC_X OUT
8KB
SRAM
BUSACK
BUSREQ
INSTRD
Bus
Controller
SCL
I2C
Serial
Interface
SDA
IORQ
MREQ
RD
DATA[7:0]
ADDR[23:0]
WR
NMI
SCK
SPI
Serial
Parallel
Interface
SS
MISO
eZ80
CPU
HALT_SLP
MOSI
256KB
Flash
Memory
JTAG/ZDI
Debug
Interface
JTAG/ZDI Signals (5)
WP
WAIT
CTS0/1
Interrupt
Vector
(8:0)
DSR0/1
UART
Universal
Asynchronous
Receiver/
Transmitter
(2)
DCD0/1
DTR0/1
RI0/1
RTS0/1
8KB
SRAM
Chip Select
and
Wait State
Generator
Interrupt
Controller
CS0
CS1
CS2
CS3
RxD0/1
DATA[7:0]
TxD0/1
ADDR[23:0]
WDT
Watch-Dog
Timer
POR/VBO
Internal
RC
Osc.
RESET
OC0/1/2/3
PWM0/1/2/3
PWM0/1/2/3
EC0/1
TOUT0/2
IC0/1/2/3
PLL_V
Programmable
Reload
Timer/Counter
(4)
LOOP_FILT
X
PHI
Crystal
Oscillator
PLL, and
System Clock
Generator
X
PD[7:0]
PC[7:0]
PA[7:0]
GPIO
8-Bit GeneralPurpose
I/O Port
(4)
PB[7:0]
TxD0/1
TxD0/1
IrDA
Encoder/
Decoder
Figure 1. eZ80F91 Block Diagram
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
4
Pin Description
Table 1 lists the pin configuration of the eZ80F91 device in the 144-BGA package.
Table 1. eZ80F91 144-BGA Pin Configuration
12
11
10
9
8
7
6
5
A SDA
SCL
PA0
PA4
PA7
COL
TxD0
VDD
B
VSS
PHI
PA1
PA3
VDD
TxD3
Tx_EN
C PB6
PB7
VDD
PA5
VSS
TxD2
D PB1
PB3
PB5
VSS
CRS
E PC7
VDD
PB0
PB4
F
PC3
PC4
PC5
G
VSS
PC0
H XOUT XIN
J
VSS
4
3
2
1
Rx_DV MDC
WPn
A0
VSS
RxD1 MDIO
A2
A1
Tx_CLK
Rx_
CLK
RxD3
A3
VSS
VDD
TxD1
Rx_ER
RxD2
A4
A8
A6
A7
PA2
Tx_ER
RxD0
A5
A11
VSS
VDD
A10
VSS
PB2
PA6
A9
A17
A15
A14
A13
A12
PC1
PC2
PC6
PLL_
VSS
VSS
A23
A20
VSS
VDD
A16
PLL_
VDD
VDD
PD7
TMS
VSS
D5
VSS
A21
A19
A18
RTC_
VDD
NMIn
WRn
D2
CS0n
VDD
A22
VSS
VDD
RESETn
RDn
VDD
D1
WAITn
VDD LOOP
FILT_
OUT
PD4 TRIGOUT
K PD5
PD6
TDI
L
PD2 TRSTn TCK
RTC_
XOUT
BUSACKn
MREQn
D6
D4
D0
CS3n
VSS
RTC_
XIN
BUSREQn INSTRDn IORQn
D7
D3
VSS
VDD
PD1
M PD0
PD3
TDO
HALT
_
SLPn
CS2n CS1n
Note: Lowercase n suffix indicates an active-low signal in this table only
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
5
PHI
110 SCL
SDA
10
144-Pin LQFP
20
VSS
HALT_SLP
TMS
TCK
TRIGOUT
TDI
TDO 70
TRST
RTC_XOUT
RTC_VDD
VDD
VSS 60
RTC_XIN
IORQ
MREQ 50
RD
WR
INSTRD
WAIT
RESET
NMI
BUSREQ
BUSACK
VDD
VSS
36
D0
D1 40
D2
D3
D4
D5
D6
D7
30
108 VSS
PB7/MOSI
PB6/MISO
PB5/IC3
PB4/IC2
PB3/SCK
PB2/SS
PB1/IC1
100 PB0/IC0/EC0
VSS
VDD
PC7/RI1
PC6/DCD1
PC5/DSR1
PC4/DTR1
PC3/CTS1
PC2/RTS1
PC1/RxD1
90 PC0/TxD1
VSS
VDD
PLL_VDD
XIN
XOUT
PLL_VSS
LOOP_FILT
VSS
VDD
80 PD7/RI0
PD6/DCD0
PD5/DSR0
PD4/DTR0
PD3/CTS0
PD2/RTS0
PD1/RxD0/IR_RxD
73 PD0/TxD0/IR_TxD
VSS
VSS
VDD
PA7/PWM3
120 PA6/PWM2/EC1
PA5/PWM1/TOUT2
PA4/PWM0/TOUT0
PA3/PWM3/OC3
PA2/PWM2/OC2
PA1/PWM1/OC1
PA0/PWM0/OC0
VSS
VDD
VSS
VDD
Tx_ER
Tx_CLK
130 Tx_EN
TxD0
TxD1
TxD2
TxD3
COL
CRS
1
VDD
VSS
A0
A1
A2
A3
A4
VDD
VSS
A5
A6
A7
A8
A9
A10
VDD
VSS
A11
A12
A13
A14
A15
A16
VDD
VSS
A17
A18
A19
A20
A21
A22
A23
VDD
VSS
CS0
CS1
CS2
CS3
144 WP
MDIO
MDC
RxD3
140 RxD2
RxD1
RxD0
Rx_DV
Rx_CLK
Rx_ER
Figure 2 displays the pin layout of the eZ80F91 device in the 144-pin LQFP package.
Figure 2. 144-Pin LQFP Configuration of the eZ80F91
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
6
Pin Characteristics
Table 2 lists the pins and functions of the eZ80F91 MCU’s 144-pin LQFP package and
144-BGA package.
Table 2. Pin Identification on the eZ80F91 Device
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
1
A1
ADDR0
Address Bus
Bidirectional
2
B1
ADDR1
Address Bus
Bidirectional
3
B2
ADDR2
Address Bus
Bidirectional
4
C3
ADDR3
Address Bus
Bidirectional
5
D4
ADDR4
Address Bus
Bidirectional
6
C1
VDD
Power Supply
Power Supply.
7
C2
VSS
Ground
Ground.
8
E5
ADDR5
Address Bus
Bidirectional
9
D2
ADDR6
Address Bus
Bidirectional
10
D1
ADDR7
Address Bus
Bidirectional
11
D3
ADDR8
Address Bus
Bidirectional
12
F6
ADDR9
Address Bus
Bidirectional
13
E1
ADDR10
Address Bus
Bidirectional
14
E2
VDD
Power Supply
Power Supply.
15
E3
VSS
Ground
Ground.
16
E4
ADDR11
Address Bus
PS019215-0910
Bidirectional
Configured as an output in normal
operation. The address bus selects a
location in memory or I/O space to be
read or written. Configured as an input
during bus acknowledge cycles.
Drives the Chip Select/Wait State
Generator block to generate Chip
Selects.
Configured as an output in normal
operation. The address bus selects a
location in memory or I/O space to be
read or written. Configured as an input
during bus acknowledge cycles.
Drives the Chip Select/Wait State
Generator block to generate Chip
Selects.
Configured as an output in normal
operation. The address bus selects a
location in memory or I/O space to be
read or written. Configured as an input
during bus acknowledge cycles.
Drives the Chip Select/Wait State
Generator block to generate Chip
Selects.
Architectural Overview
eZ80F91 MCU
Product Specification
7
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
17
F1
ADDR12
Address Bus
Bidirectional
18
F2
ADDR13
Address Bus
Bidirectional
19
F3
ADDR14
Address Bus
Bidirectional
20
F4
ADDR15
Address Bus
Bidirectional
21
G1
ADDR16
Address Bus
Bidirectional
22
G2
VDD
Power Supply
Power Supply.
23
G3
VSS
Ground
Ground.
24
F5
ADDR17
Address Bus
Bidirectional
25
H1
ADDR18
Address Bus
Bidirectional
26
H2
ADDR19
Address Bus
Bidirectional
27
G4
ADDR20
Address Bus
Bidirectional
28
H3
ADDR21
Address Bus
Bidirectional
29
J1
ADDR22
Address Bus
Bidirectional
30
G5
ADDR23
Address Bus
Bidirectional
31
J2
VDD
Power Supply
Power Supply.
32
H4
VSS
Ground
Ground.
33
J3
CS0
Chip Select 0
Output, Active
Low
CS0 Low indicates that an access is
occurring in the defined CS0 memory
or I/O address space.
34
K1
CS1
Chip Select 1
Output, Active
Low
CS1 Low indicates that an access is
occurring in the defined CS1 memory
or I/O address space.
35
K2
CS2
Chip Select 2
Output, Active
Low
CS2 Low indicates that an access is
occurring in the defined CS2 memory
or I/O address space.
36
L1
CS3
Chip Select 3
Output, Active
Low
CS3 Low indicates that an access is
occurring in the defined CS3 memory
or I/O address space.
37
M1
VDD
Power Supply
Power Supply.
38
M2
VSS
Ground
Ground.
PS019215-0910
Configured as an output in normal
operation. The address bus selects a
location in memory or I/O space to be
read or written. Configured as an input
during bus acknowledge cycles.
Drives the Chip Select/Wait State
Generator block to generate Chip
Selects.
Configured as an output in normal
operation. The address bus selects a
location in memory or I/O space to be
read or written. Configured as an input
during bus acknowledge cycles.
Drives the Chip Select/Wait State
Generator block to generate Chip
Selects.
Architectural Overview
eZ80F91 MCU
Product Specification
8
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
39
L2
DATA0
Data Bus
Bidirectional
40
K3
DATA1
Data Bus
Bidirectional
41
J4
DATA2
Data Bus
Bidirectional
42
M3
DATA3
Data Bus
Bidirectional
43
L3
DATA4
Data Bus
Bidirectional
44
H5
DATA5
Data Bus
Bidirectional
45
L4
DATA6
Data Bus
Bidirectional
46
M4
DATA7
Data Bus
Bidirectional
47
K4
VDD
Power Supply
Power Supply.
48
G6
VSS
Ground
Ground.
49
M5
IORQ
Input/Output
Request
Bidirectional,
Active Low
IORQ indicates that the CPU is
accessing a location in I/O space. RD
and WR indicate the type of access.
The eZ80F91 device does not drive
this line during RESET. It is an input
during bus acknowledge cycles.
50
L5
MREQ
Memory
Request
Bidirectional,
Active Low
MREQ Low indicates that the CPU is
accessing a location in memory. The
RD, WR, and INSTRD signals indicate
the type of access. The eZ80F91
device does not drive this line during
RESET. It is an input during bus
acknowledge cycles.
51
K5
RD
Read
Output, 
Active Low
RD Low indicates that the eZ80F91
device is reading from the current
address location. This pin is in a highimpedance state during bus
acknowledge cycles.
52
J5
WR
Write
Output, Active
Low
WR indicates that the CPU is writing
to the current address location. This
pin is in a high-impedance state
during bus acknowledge cycles.
PS019215-0910
The data bus transfers data to and
from I/O and memory devices. The
eZ80F91 drives these lines only
during Write cycles when the
eZ80F91 is the bus master.
Architectural Overview
eZ80F91 MCU
Product Specification
9
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
53
M6
INSTRD
Instruction
Output, Active
Read Indicator Low
54
L6
WAIT
WAIT Request Schmitt-trigger
Driving the WAIT pin Low forces the
input, Active Low CPU to wait additional clock cycles for
an external peripheral or external
memory to complete its Read or Write
operation.
55
K6
RESET
Reset
Bidirectional,
Active Low
Schmitt-trigger
input or open
drain output
This signal is used to initialize the
eZ80F91, and/or allow the ez80F91 to
signal when it resets. See reset
section for the timing details. This
Schmitt-trigger input allows for RC rise
times.
56
J6
NMI
Nonmaskable
Interrupt
Schmitt-trigger
input, Active Low,
edge-triggered
interrupt
The NMI input is a higher priority input
than the maskable interrupts. It is
always recognized at the end of an
instruction, regardless of the state of
the interrupt enable control bits. This
input includes a Schmitt- trigger to
allow for RC rise times.
57
M7
BUSREQ
Bus Request
Schmitt-trigger
External devices request the eZ80F91
input, Active Low device to release the memory
interface bus for their use by driving
this pin Low.
58
L7
BUSACK
Bus
Acknowledge
Output, Active
Low
59
K7
VDD
Power Supply
Power Supply.
60
H6
VSS
Ground
Ground.
PS019215-0910
Signal Direction Description
INSTRD (with MREQ and RD)
indicates the eZ80F91 device is
fetching an instruction from memory.
This pin is in a high-impedance state
during bus acknowledge cycles.
The eZ80F91 device responds to a
Low on BUSREQ making the address,
data, and control signals high
impedance, and by driving the
BUSACK line Low. During bus
acknowledge cycles ADDR[23:0],
IORQ, and MREQ are inputs.
Architectural Overview
eZ80F91 MCU
Product Specification
10
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
61
M8
RTC_XIN
Real-Time
Clock Crystal
Input
Input
This pin is the input to the low-power
32 kHz crystal oscillator for the Realtime clock. If the Real-time clock is
disabled or not used, this input must
be left floating or tied to VSS to
minimize any input current leakage.
62
L8
RTC_XOUT
Real-Time
Clock Crystal
Output
Bidirectional
This pin is the output from the lowpower 32 kHz crystal oscillator for the
Real-Time Clock. This pin is an input
when the RTC is configured to
operate from 50/60 Hz input clock
signals and the 32 kHz crystal
oscillator is disabled.
63
J7
RTC_VDD
Real-Time
Clock Power
Supply
Power supply for the Real-Time Clock
and associated 32 kHz oscillator.
Isolated from the power supply to the
remainder of the chip. A battery is
connected to this pin to supply
constant power to the Real-Time
Clock and 32 kHz oscillator. If the
Real-time clock is disabled or not
used this output must be tied to Vdd.
64
K8
VSS
Ground
Ground.
65
M9
HALT_SLP
HALT and
SLEEP
Indicator
Output, Active
Low
A Low on this pin indicates that the
CPU has entered either HALT or
SLEEP mode because of execution of
either a HALT or SLP instruction.
66
H7
TMS
JTAG Test
Mode Select
Input
JTAG Mode Select Input.
67
L9
TCK
JTAG Test
Clock
Input
JTAG and ZDI clock input.
68
J8
TRIGOUT
JTAG Test
Output
Trigger Output
Active High trigger event indicator.
69
K9
TDI
JTAG Test
Data In
JTAG data input pin. Functions as ZDI
data I/O pin when JTAG is disabled.
This pin has an internal pull-up
resistor in the pad.
PS019215-0910
Bidirectional
Architectural Overview
eZ80F91 MCU
Product Specification
11
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
70
M10
TDO
JTAG Test
Data Out
Output
71
L10
TRST
JTAG Reset
Schmitt-trigger
JTAG reset input pin.
input, Active Low
72
M11
VSS
Ground
73
M12
PD0
GPIO Port D
TxD0
UART
Output
Transmit Data
This pin is used by the UART to
transmit asynchronous serial data.
This signal is multiplexed with PD0.
IR_TxD
IrDA Transmit
Data
Output
This pin is used by the IrDA encoder/
decoder to transmit serial data. This
signal is multiplexed with PD0.
PD1
GPIO Port D
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
RxD0
Receive Data
Input
This pin is used by the UART to
receive asynchronous serial data.
This signal is multiplexed with PD1.
IR_RxD
IrDA Receive
Data
Input
This pin is used by the IrDA encoder/
decoder to receive serial data. This
signal is multiplexed with PD1.
74
L12
PS019215-0910
JTAG data output pin.
Ground.
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
Architectural Overview
eZ80F91 MCU
Product Specification
12
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
75
PD2
GPIO Port D
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
RTS0
Request to
Send
Output, 
Active Low
Modem control signal from UART.
This signal is multiplexed with PD2.
PD3
GPIO Port D
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
CTS0
Clear to Send
Input, Active Low Modem status signal to the UART.
This signal is multiplexed with PD3.
PD4
GPIO Port D
Bidirectional
DTR0
Data Terminal Output, 
Ready
Active Low
76
77
L11
K10
J9
PS019215-0910
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
Modem control signal to the UART.
This signal is multiplexed with PD4.
Architectural Overview
eZ80F91 MCU
Product Specification
13
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
78
PD5
GPIO Port D
Bidirectional
DSR0
Data Set
Ready
Input, Active Low Modem status signal to the UART.
This signal is multiplexed with PD5.
PD6
GPIO Port D
Bidirectional
DCD0
Data Carrier
Detect
Input, Active Low Modem status signal to the UART.
This signal is multiplexed with PD6.
PD7
GPIO Port D
Bidirectional
RI0
Ring Indicator
Input, Active Low Modem status signal to the UART.
This signal is multiplexed with PD7.
79
80
K12
K11
H8
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port D pin,
when programmed as output is
selected to be an open-drain or opensource output. Port D is multiplexed
with one UART.
81
J11
VDD
Power Supply
Power Supply.
82
J12
VSS
Ground
Ground.
83
J10
LOOP_FILT PLL Loop Filter Analog
Loop Filter pin for the Analog PLL.
84
G7
PLL_VSS
Ground
Ground for Analog PLL.
85
H12
XOUT
System Clock
Oscillator
Output
PS019215-0910
Output
This pin is the output of the onboard
crystal oscillator. When used, a crystal
must be connected between XIN and
XOUT.
Architectural Overview
eZ80F91 MCU
Product Specification
14
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
86
H11
XIN
System Clock Input
Oscillator Input
This pin is the input to the onboard
crystal oscillator for the primary
system clock. If an external oscillator
is used, its clock output must be
connected to this pin. When a crystal
is used, it must be connected between
XIN and XOUT.
87
H10
PLL_VDD
Power Supply
Power Supply for Analog PLL.
88
H9
VDD
Power Supply
Power Supply.
89
G12
VSS
Ground
Ground.
90
G11
PC0
GPIO Port C
TxD1
Transmit Data Output
PC1
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
individually programmed as input or
Schmitt-trigger
output and is also used individually as
input
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
RxD1
Receive Data
Schmitt-trigger
input
91
G10
PS019215-0910
Signal Direction Description
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
This pin is used by the UART to
transmit asynchronous serial data.
This signal is multiplexed with PC0.
This pin is used by the UART to
receive asynchronous serial data.
This signal is multiplexed with PC1.
Architectural Overview
eZ80F91 MCU
Product Specification
15
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
92
PC2
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
RTS1
Request to
Send
Output, Active
Low
PC3
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
CTS1
Clear to Send
Schmitt-trigger
Modem status signal to the UART.
input, Active Low This signal is multiplexed with PC3.
PC4
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
DTR1
Data Terminal Output, Active
Ready
Low
93
94
G9
F12
F11
PS019215-0910
Modem control signal from UART.
This signal is multiplexed with PC2.
Modem control signal to the UART.
This signal is multiplexed with PC4.
Architectural Overview
eZ80F91 MCU
Product Specification
16
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
95
PC5
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
DSR1
Data Set
Ready
Schmitt-trigger
Modem status signal to the UART.
input, Active Low This signal is multiplexed with PC5.
PC6
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
DCD1
Data Carrier
Detect
Schmitt-trigger
Modem status signal to the UART.
input, Active Low This signal is multiplexed with PC6.
PC7
GPIO Port C
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port C pin,
when programmed as output is
selected to be an open-drain or opensource output. Port C is multiplexed
with one UART.
RI1
Ring Indicator
Schmitt-trigger
Modem status signal to the UART.
input, Active Low This signal is multiplexed with PC7.
96
97
F10
G8
E12
98
E11
VDD
Power Supply
Power Supply.
99
F9
VSS
Ground
Ground.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
17
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
100
PB0
GPIO Port B
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
IC0
Input Capture
Schmitt-trigger
input
EC0
Event Counter Schmitt-trigger
input
PB1
GPIO Port B
Bidirectional with This pin is used for GPIO. It is
individually programmed as input or
Schmitt-trigger
output and is also used individually as
input
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
IC1
Input Capture
Schmitt-trigger
input
PB2
GPIO Port B
Bidirectional with This pin is used for GPIO. It is
individually programmed as input or
Schmitt-trigger
output and is also used individually as
input
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
SS
SPI Slave
Select
Schmitt-trigger
The slave select input line is used to
input, Active Low select a slave device in SPI mode.
This signal is multiplexed with PB2.
101
102
E10
D12
F8
PS019215-0910
Input Capture A Signal to Timer 1.
This signal is multiplexed with PB0.
Event Counter Signal to Timer 1. This
signal is multiplexed with PB0.
Input Capture B Signal to Timer 1.
This signal is multiplexed with PB1.
Architectural Overview
eZ80F91 MCU
Product Specification
18
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
103
PB3
GPIO Port B
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
SCK
SPI Serial
Clock
Bidirectional with SPI serial clock. This signal is
Schmitt-trigger
multiplexed with PB3.
input
PB4
GPIO Port B
Bidirectional with This pin is used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
IC2
Input Capture
Schmitt-trigger
input
PB5
GPIO Port B
Bidirectional with This pin is used for GPIO. It is
individually programmed as input or
Schmitt-trigger
output and is also used individually as
input
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
IC3
Input Capture
Schmitt-trigger
input
104
105
D11
E9
D10
PS019215-0910
Input Capture A Signal to Timer 3.
This signal is multiplexed with PB4.
Input Capture B Signal to Timer 3.
This signal is multiplexed with PB5.
Architectural Overview
eZ80F91 MCU
Product Specification
19
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
106
PB6
GPIO Port B
Bidirectional with This pin is be used for GPIO. It is
Schmitt-trigger
individually programmed as input or
input
output and is also used individually as
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
MISO
SPI Master-In/ Bidirectional with The MISO line is configured as an
Slave-Out
Schmitt-trigger
input when the eZ80F91 device is an
input
SPI master device and as an output
when eZ80F91 is an SPI slave device.
This signal is multiplexed with PB6.
PB7
GPIO Port B
MOSI
SPI Master Out Bidirectional with The MOSI line is configured as an
output when the eZ80F91 device is an
Slave In
Schmitt-trigger
SPI master device and as an input
input
when the eZ80F91 device is an SPI
slave device. This signal is
multiplexed with PB7.
107
C12
C11
Bidirectional with This pin is used for GPIO. It is
individually programmed as input or
Schmitt-trigger
output and is also used individually as
input
an interrupt input. Each Port B pin,
when programmed as output is
selected to be an open-drain or opensource output.
108
B12
VSS
Ground
Ground.
109
A12
SDA
I2C Serial Data Bidirectional
This pin carries the I2C data signal.
110
A11
SCL
I2C Serial
Clock
Bidirectional
This pin is used to receive and
transmit the I2C clock.
111
B11
PHI
System Clock
Output
This pin is an output driven by the
internal system clock. It is used by the
system for synchronization with the
eZ80F91 device.
112
C10
VDD
Power Supply
Power Supply.
113
D9
VSS
Ground
Ground.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
20
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
114
PA0
GPIO Port A
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
PWM0
PWM 
Output 0
Output
This pin is used by Timer 3 for PWM
0. This signal is multiplexed with PA0.
OC0
Output
Compare 0
Output
This pin is used by Timer 3 for Output
Compare 0. This signal is multiplexed
with PA0.
PA1
GPIO Port A
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
PWM1
PWM 
Output 1
Output
This pin is used by Timer 3 for PWM
1. This signal is multiplexed with PA1.
OC1
Output
Compare 1
Output
This pin is used by Timer 3 for Output
Compare 1. This signal is multiplexed
with PA1.
PA2
GPIO Port A
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
PWM2
PWM 
Output 2
Output
This pin is used by Timer 3 for PWM
2. This signal is multiplexed with PA2.
OC2
Output
Compare 2
Output
This pin is used by Timer 3 for Output
Compare 2. This signal is multiplexed
with PA2.
115
116
A10
B10
E8
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
21
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
117
PA3
GPIO Port A
Bidirectional
PWM3
PWM Output 3 Output
This pin is used by Timer 3 for PWM
3. This signal is multiplexed with PA3.
OC3
Output
Compare 3
Output
This pin is used by Timer 3 for Output
Compare 3 This signal is multiplexed
with PA3.
PA4
GPIO Port A
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
PWM0
PWM Output 0 Output
Inverted
This pin is used by Timer 3 for
negative PWM 0. This signal is
multiplexed with PA4.
TOUT0
Timer Out
Output
This pin is used by Timer 0 timer-out
signal. This signal is multiplexed with
PA4.
PA5
GPIO Port A
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
PWM1
PWM Output 1 Output
Inverted
This pin is used by Timer 3 for
negative PWM 1. This signal is
multiplexed with PA5.
TOUT2
Timer Out
This pin is used by the Timer 2 timerout signal. This signal is multiplexed
with PA5.
118
119
B9
A9
C9
PS019215-0910
Output
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
Architectural Overview
eZ80F91 MCU
Product Specification
22
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
120
PA6
GPIO Port A
Bidirectional
PWM2
PWM Output 2 Output
Inverted
This pin is used by Timer 3 for
negative PWM 2. This signal is
multiplexed with PA6.
EC1
Event Counter Input
Event Counter Signal to Timer 2. This
signal is multiplexed with PA6.
PA7
GPIO Port A
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
PWM3
PWM Output 3 Output
Inverted
This pin is used by Timer 3 for
negative PWM 3. This signal is
multiplexed with PA7.
121
F7
A8
Bidirectional
This pin is used for GPIO. It is
individually programmed as input or
output and is also used individually as
an interrupt input. Each Port A pin,
when programmed as output is
selected to be an open-drain or opensource output.
122
B8
VDD
Power Supply
Power Supply.
123
C8
VSS
Ground
Ground.
124
D8
CRS
MII Carrier
Sense
Input
This pin is used by the EMAC for the
MII Interface to the PHY (physical
layer). Carrier Sense is an
asynchronous signal.
125
A7
COL
MII Collision
Detect
Input
This pin is used by the EMAC for the
MII Interface to the PHY. Collision
Detect is an asynchronous signal.
126
B7
TxD3
MII Transmit
Data
Output
This pin is used by the EMAC for the
MII Interface to the PHY. Transmit
Data is synchronous to the risingedge of Tx_CLK.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
23
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
127
C7
TxD2
MII Transmit
Data
Output
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Transmit Data is synchronous to the
rising-edge of Tx_CLK.
128
D7
TxD1
MII Transmit
Data
Output
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Transmit Data is synchronous to the
rising-edge of Tx_CLK.
129
A6
TxD0
MII Transmit
Data
Output
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Transmit Data is synchronous to the
rising-edge of Tx_CLK.
130
B6
Tx_EN
MII Transmit
Enable
Output
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Transmit Enable is synchronous to the
rising-edge of Tx_CLK.
131
C6
Tx_CLK
MII Transmit
Clock
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Transmit Clock is the Nibble or
Symbol Clock provided by the MII
PHY interface.
132
E7
Tx_ER
MII Transmit
Error
Output
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Transmit Error is synchronous to the
rising-edge of Tx_CLK.
133
A5
VDD
Power Supply
Power Supply.
134
B5
VSS
Ground
Ground.
135
D6
Rx_ER
MII Receive
Error
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Error is provided by the MII
PHY interface synchronous to the
rising-edge of Rx_CLK.
136
C5
Rx_CLK
MII Receive
Clock
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Clock is the Nibble or Symbol
Clock provided by the MII PHY
interface.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
24
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
137
A4
Rx_DV
MII Receive
Data Valid
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Data Valid is provided by the
MII PHY interface synchronous to the
rising-edge of Rx_CLK.
138
E6
RxD0
MII Receive
Data
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Data is provided by the MII
PHY interface synchronous to the
rising-edge of Rx_CLK.
139
B4
RxD1
MII Receive
Data
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Data is provided by the MII
PHY interface synchronous to the
rising-edge of Rx_CLK.
140
D5
RxD2
MII Receive
Data
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Data is provided by the MII
PHY interface synchronous to the
rising-edge of Rx_CLK.
141
C4
RxD3
MII Receive
Data
Input
This pin is used by the Ethernet MAC
for the MII Interface to the PHY.
Receive Data is provided by the MII
PHY interface synchronous to the
rising-edge of Rx_CLK.
142
A3
MDC
MII
Management
Data Clock
Output
This pin is used by the Ethernet MAC
for the MII Management Interface to
the PHY. The Ethernet MAC provides
the MII Management Data Clock to
the MII PHY interface.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
25
Table 2. Pin Identification on the eZ80F91 Device (Continued)
LQFP BGA
Pin No Pin No
Symbol
Function
Signal Direction Description
143
B3
MDIO
MII
Management
Data
Bidirectional
144
A2
WP
Write Protect
Schmitt-trigger
The Write Protect input is used by the
input, Active Low Flash Controller to protect the Boot
Block from Write and ERASE
operations.
This pin is used by the Ethernet MAC
for the MII Management Interface to
the PHY. The Ethernet MAC sends
and receives the MII Management
Data to and from the MII PHY
interface.
System Clock Source Options
The following section describes the system clock source options.
System Clock—The eZ80F91 device’s internal clock, SCLK, is responsible for clocking
all internal logic. The SCLK source can be an external crystal oscillator, an internal PLL,
or an internal 32 kHz RTC oscillator. The SCLK source is selected by PLL Control Register 0. RESET default is provided by the external crystal oscillator. For more details on
CLK_MUX values in the PLL Control Register 0, see Table 154 on page 269.
PHI—PHI is a device output driven by SCLK that is used for system synchronization to
the eZ80F91 device. PHI is used as the reference clock for all AC characteristics, see
page 344.
External Crystal Oscillator—An externally-driven oscillator operates in two modes. In
one mode, the XIN pin is driven by a oscillator from DC up to 50 MHz when the XOUT pin
is not connected. In the other mode, the XIN and XOUT pins are driven by a crystal circuit.
Crystals recommended by Zilog® are defined to be a 50 MHz–3 overtone circuit or 1–10
MHz range fundamental for PLL operation. For details, see On-Chip Oscillators on page
335.
Real Time Clock—An internal 32 kHz real-time clock crystal oscillator driven by either
the on-chip 32768 Hz crystal oscillator or a 50/60 Hz power-line frequency input. While
intended for timekeeping, the RTC 32 kHz oscillator is selected as an SCLK. RTC_VDD
and RTC_VSS provides an isolated power supply to ensure RTC operation in the event of
loss of line power when a battery is provided. For more details, see On-Chip Oscillators on
page 335.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
26
PLL Clock—The eZ80F91 internal PLL driven by external crystals or external crystal
oscillators in the range of 1 MHz to 10 MHz generates an SCLK up to 50 MHz. For moredetails, see Phase-Locked Loop on page 265.
SCLK Source Selection Example
For additional SCLK source selection examples, refer to Crystal Oscillator/Resonator
Guidelines for eZ80® and eZ80Acclaim!® Devices Technical Note (TN0013) available on
www.zilog.com.
PS019215-0910
Architectural Overview
eZ80F91 MCU
Product Specification
27
Register Map
All on-chip peripheral registers are accessed in the I/O address space. All I/O operations
employ 16-bit addresses. The upper byte of the 24-bit address bus is undefined during all
I/O operations (ADDR[23:16] = XX). All I/O operations using 16-bit addresses within the
0000h–00FFh range are routed to the on-chip peripherals. External I/O chip selects are
not generated if the address space programmed for the I/O chip selects overlap the
0000h–00FFh address range.
Registers at unused addresses within the 0000h–00FFh range assigned to on-chip peripherals are not implemented. Read access to such addresses returns unpredictable values and
Write access produces no effect. Table 3 lists the register map for the eZ80F91 device.
Table 3. Register Map
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
Product ID
0000
ZDI_ID_L
eZ80® Product ID Low Byte Register
08
R
252
0001
ZDI_ID_H
eZ80 Product ID High Byte Register
00
R
252
0002
ZDI_ID_REV
eZ80 Product ID Revision Register
XX
R
252
Interrupt Priority
0010
INT_P0
Interrupt Priority Register—Byte 0
00
R/W
61
0011
INT_P1
Interrupt Priority Register—Byte 1
00
R/W
61
0012
INT_P2
Interrupt Priority Register—Byte 2
00
R/W
61
0013
INT_P3
Interrupt Priority Register—Byte 3
00
R/W
61
0014
INT_P4
Interrupt Priority Register—Byte 4
00
R/W
61
0015
INT_P5
Interrupt Priority Register—Byte 5
00
R/W
61
Ethernet Media Access Controller
0020
EMAC_TEST
EMAC Test Register
00
R/W
298
0021
EMAC_CFG1
EMAC Configuration Register
00
R/W
299
0022
EMAC_CFG2
EMAC Configuration Register
37
R/W
301
0023
EMAC_CFG3
EMAC Configuration Register
0F
R/W
302
0024
EMAC_CFG4
EMAC Configuration Register
00
R/W
303
0025
EMAC_STAD_0
EMAC Station Address—Byte 0
00
R/W
304
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
28
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
0026
EMAC_STAD_1
EMAC Station Address—Byte 1
00
R/W
304
0027
EMAC_STAD_2
EMAC Station Address—Byte 2
00
R/W
304
0028
EMAC_STAD_3
EMAC Station Address—Byte 3
00
R/W
304
0029
EMAC_STAD_4
EMAC Station Address—Byte 4
00
R/W
304
002A
EMAC_STAD_5
EMAC Station Address—Byte 5
00
R/W
304
002B
EMAC_TPTV_L
EMAC Transmit Pause 
Timer Value—Low Byte
00
R/W
305
002C
EMAC_TPTV_H
EMAC Transmit Pause 
Timer Value—High Byte
00
R/W
305
002D
EMAC_IPGT
EMAC Inter-Packet Gap
15
R/W
306
002E
EMAC_IPGR1
EMAC Non-Back-Back IPG
0C
R/W
308
002F
EMAC_IPGR2
EMAC Non-Back-Back IPG
12
R/W
308
0030
EMAC_MAXF_L
EMAC Maximum Frame 
Length—Low Byte
00
R/W
309
0031
EMAC_MAXF_H
EMAC Maximum Frame 
Length—High Byte
06
R/W
310
0032
EMAC_AFR
EMAC Address Filter Register
00
R/W
311
0033
EMAC_HTBL_0
EMAC Hash Table—Byte 0
00
R/W
312
0034
EMAC_HTBL_1
EMAC Hash Table—Byte 1
00
R/W
312
0035
EMAC_HTBL_2
EMAC Hash Table—Byte 2
00
R/W
312
0036
EMAC_HTBL_3
EMAC Hash Table—Byte 3
00
R/W
312
0037
EMAC_HTBL_4
EMAC Hash Table—Byte 4
00
R/W
312
0038
EMAC_HTBL_5
EMAC Hash Table—Byte 5
00
R/W
312
0039
EMAC_HTBL_6
EMAC Hash Table—Byte 6
00
R/W
312
003A
EMAC_HTBL_7
EMAC Hash Table—Byte 7
00
R/W
312
003B
EMAC_MIIMGT
EMAC MII Management Register
00
R/W
313
003C
EMAC_CTLD_L
EMAC PHY Configuration 
Data—Low Byte
00
R/W
314
003D
EMAC_CTLD_H
EMAC PHY Configuration 
Data—High Byte
00
R/W
315
003E
EMAC_RGAD
EMAC PHY Register Address Register
00
R/W
315
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
29
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
003F
EMAC_FIAD
EMAC PHY Unit Select Address
Register
00
R/W
316
0040
EMAC_PTMR
EMAC Transmit Polling Timer Register
00
R/W
316
0041
EMAC_RST
EMAC Reset Control Register
20
R/W
317
0042
EMAC_TLBP_L
EMAC Transmit Lower Boundary
Pointer—Low Byte
00
R/W
318
0043
EMAC_TLBP_H
EMAC Transmit Lower Boundary
Pointer—High Byte
00
R/W
318
0044
EMAC_BP_L
EMAC Boundary Pointer—Low Byte
00
R/W
319
0045
EMAC_BP_H
EMAC Boundary Pointer—High Byte
C0
R/W
319
0046
EMAC_BP_U
EMAC Boundary Pointer—Upper Byte
FF
R/W
319
0047
EMAC_RHBP_L
EMAC Receive High Boundary
Pointer—Low Byte
00
R/W
320
0048
EMAC_RHBP_H
EMAC Receive High Boundary
Pointer—High Byte
00
R/W
321
0049
EMAC_RRP_L
EMAC Receive Read 
Pointer—Low Byte
00
R/W
321
004A
EMAC_RRP_H
EMAC Receive Read 
Pointer—High Byte
00
R/W
322
004B
EMAC_BUFSZ
EMAC Buffer Size Register
00
R/W
322
004C
EMAC_IEN
EMAC Interrupt Enable Register
00
R/W
323
004D
EMAC_ISTAT
EMAC Interrupt Status Register
00
R/W
325
004E
EMAC_PRSD_L
EMAC PHY Read Status 
Data—Low Byte
00
R/W
326
004F
EMAC_PRSD_H
EMAC PHY Read Status 
Data—High Byte
00
R/W
327
0050
EMAC_MIISTAT
EMAC MII Status Register
00
R/W
327
0051
EMAC_RWP_L
EMAC Receive Write 
Pointer—Low Byte
00
R/W
328
0052
EMAC_RWP_H
EMAC Receive Write 
Pointer—High Byte
00
R/W
329
0053
EMAC_TRP_L
EMAC Transmit Read 
Pointer—Low Byte
00
R/W
329
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
30
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
0054
EMAC_TRP_H
EMAC Transmit Read 
Pointer—High Byte
00
R/W
330
0055
EMAC_BLKSLFT_L
EMAC Receive Blocks Left 
Register—Low Byte
20
R/W
330
0056
EMAC_BLKSLFT_H
EMAC Receive Blocks Left 
Register—High Byte
00
R/W
331
0057
EMAC_FDATA_L
EMAC FIFO Data—Low Byte
XX
R/W
332
0058
EMAC_FDATA_H
EMAC FIFO Data—High Byte
0X
R/W
332
0059
EMAC_FFLAGS
EMAC FIFO Flags Register
33
R/W
333
005C
PLL_DIV_L
PLL Divider Register—Low Byte
00
W
268
005D
PLL_DIV_H
PLL Divider Register—High Byte
00
W
269
005E
PLL_CTL0
PLL Control Register 0
00
R/W
269
005F
PLL_CTL1
PLL Control Register 1
00
R/W
271
PLL
Timers and PWM
0060
TMR0_CTL
Timer 0 Control Register
00
R/W
132
0061
TMR0_IER
Timer 0 Interrupt Enable Register
00
R/W
133
0062
TMR0_IIR
Timer 0 Interrupt Identification Register
00
R/W
135
0063
TMR0_DR_L
Timer 0 Data Register—Low Byte
XX
R
136
TMR0_RR_L
Timer 0 Reload Register—Low Byte
XX
W
138
TMR0_DR_H
Timer 0 Data Register—High Byte
XX
R
137
TMR0_RR_H
Timer 0 Reload Register—High Byte
XX
W
139
0065
TMR1_CTL
Timer 1 Control Register
00
R/W
132
0066
TMR1_IER
Timer 1 Interrupt Enable Register
00
R/W
133
0067
TMR1_IIR
Timer 1 Interrupt Identification Register
00
R/W
135
0068
TMR1_DR_L
Timer 1 Data Register—Low Byte
XX
R
136
TMR1_RR_L
Timer 1 Reload Register—Low Byte
XX
W
138
TMR1_DR_H
Timer 1 Data Register—High Byte
XX
R
137
TMR1_RR_H
Timer 1 Reload Register—High Byte
XX
W
139
0064
0069
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
31
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
006A
TMR1_CAP_CTL
Timer 1 Input Capture Control Register
XX
R/W
139
006B
TMR1_CAPA_L
Timer 1 Capture Value A 
Register—Low Byte
XX
R/W
140
006C
TMR1_CAPA_H
Timer 1 Capture Value A 
Register—High Byte
XX
R/W
141
006D
TMR1_CAPB_L
Timer 1 Capture Value B 
Register—Low Byte
XX
R/W
141
006E
TMR1_CAPB_H
Timer 1 Capture Value B 
Register—High Byte
XX
R/W
142
006F
TMR2_CTL
Timer 2 Control Register
00
R/W
132
0070
TMR2_IER
Timer 2 Interrupt Enable Register
00
R/W
133
0071
TMR2_IIR
Timer 2 Interrupt Identification Register
00
R/W
135
0072
TMR2_DR_L
Timer 2 Data Register—Low Byte
XX
R
136
TMR2_RR_L
Timer 2 Reload Register—Low Byte
XX
W
138
TMR2_DR_H
Timer 2 Data Register—High Byte
XX
R
137
TMR2_RR_H
Timer 2 Reload Register—High Byte
XX
W
139
0074
TMR3_CTL
Timer 3 Control Register
00
R/W
132
0075
TMR3_IER
Timer 3 Interrupt Enable Register
00
R/W
133
0076
TMR3_IIR
Timer 3 Interrupt Identification Register
00
R/W
135
0077
TMR3_DR_L
Timer 3 Data Register—Low Byte
XX
R
136
TMR3_RR_L
Timer 3 Reload Register—Low Byte
XX
W
138
TMR3_DR_H
Timer 3 Data Register—High Byte
XX
R
137
TMR3_RR_H
Timer 3 Reload Register—High Byte
XX
W
139
0079
PWM_CTL1
PWM Control Register 1
00
R/W
153
007A
PWM_CTL2
PWM Control Register 2
00
R/W
154
007B
PWM_CTL3
PWM Control Register 3
00
R/W
156
TMR3_CAP_CTL
Timer 3 Input Capture Control Register
00
R/W
139
PWM0R_L
PWM 0 Rising-Edge 
Register—Low Byte
XX
R/W
157
TMR3_CAPA_L
Timer 3 Capture Value A 
Register—Low Byte
XX
R/W
140
0073
0078
007C
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
32
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
007D
007E
007F
0080
0081
0082
0083
0084
Name
Reset
(hex)
CPU
Access
Page
No
PWM0R_H
PWM 0 Rising-Edge 
Register—High Byte
XX
R/W
157
TMR3_CAPA_H
Timer 3 Capture Value A 
Register—High Byte
XX
R/W
141
PWM1R_L
PWM 1 Rising-Edge 
Register—Low Byte
XX
R/W
157
TMR3_CAPB_L
Timer 3 Capture Value B 
Register—Low Byte
XX
R/W
141
PWM1R_H
PWM 1 Rising-Edge 
Register—High Byte
XX
R/W
157
TMR3_CAPB_H
Timer 3 Capture Value B 
Register—High Byte
XX
R/W
142
PWM2R_L
PWM 2 Rising-Edge 
Register—Low Byte
XX
R/W
157
TMR3_OC_CTL1
Timer 3 Output Compare Control
Register 1
00
R/W
132
PWM2R_H
PWM 2 Rising-Edge 
Register—High Byte
XX
R/W
157
TMR3_OC_CTL2
Timer 3 Output Compare Control
Register 2
00
R/W
132
PWM3R_L
PWM 3 Rising-Edge 
Register—Low Byte
XX
R/W
157
TMR3_OC0_L
Timer 3 Output Compare 0 Value
Register—Low Byte
XX
R/W
144
PWM3R_H
PWM 3 Rising-Edge 
Register—High Byte
XX
R/W
157
TMR3_OC0_H
Timer 3 Output Compare 0 Value
Register—High Byte
XX
R/W
145
PWM0F_L
PWM 0 Falling-Edge 
Register—Low Byte
XX
R/W
158
TMR3_OC1_L
Timer 3 Output Compare 1 Value
Register—Low Byte
XX
R/W
144
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
33
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
PWM0F_H
PWM 0 Falling-Edge 
Register—High Byte
XX
R/W
158
TMR3_OC1_H
Timer 3 Output Compare 1 Value
Register—High Byte
XX
R/W
145
PWM1F_L
PWM 1 Falling-Edge 
Register—Low Byte
XX
R/W
158
TMR3_OC2_L
Timer 3 Output Compare 2 Value
Register—Low Byte
XX
R/W
144
PWM1F_H
PWM 1 Falling-Edge 
Register—High Byte
XX
R/W
158
TMR3_OC2_H
Timer 3 Output Compare 2 Value
Register—High Byte
XX
R/W
145
PWM2F_L
PWM 2 Falling-Edge 
Register—Low Byte
XX
R/W
158
TMR3_OC3_L
Timer 3 Output Compare 3 Value
Register—Low Byte
XX
R/W
144
PWM2F_H
PWM 2 Falling-Edge 
Register—High Byte
XX
R/W
158
TMR3_OC3_H
Timer 3 Output Compare 3 Value
Register—High Byte
XX
R/W
145
008A
PWM3F_L
PWM 3 Falling-Edge 
Register—Low Byte
XX
R/W
158
008B
PWM3F_H
PWM 3 Falling-Edge 
Register—High Byte
XX
R/W
158
08/28
R/W
117
XX
W
119
0085
0086
0087
0088
0089
Watchdog Timer
0093
WDT_CTL
Watchdog Timer Control Register
0094
WDT_RR
Watchdog Timer Reset Register
General-Purpose Input/Output Ports
0096
PA_DR
Port A Data Register
XX
R/W
55
0097
PA_DDR
Port A Data Direction Register
FF
R/W
55
0098
PA_ALT1
Port A Alternate Register 1
00
R/W
56
0099
PA_ALT2
Port A Alternate Register 2
00
R/W
56
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
34
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
009A
PB_DR
Port B Data Register
XX
R/W
55
009B
PB_DDR
Port B Data Direction Register
FF
R/W
55
009C
PB_ALT1
Port B Alternate Register 1
00
R/W
56
009D
PB_ALT2
Port B Alternate Register 2
00
R/W
56
009E
PC_DR
Port C Data Register
XX
R/W
55
009F
PC_DDR
Port C Data Direction Register
FF
R/W
55
00A0
PC_ALT1
Port C Alternate Register 1
00
R/W
56
00A1
PC_ALT2
Port C Alternate Register 2
00
R/W
56
00A2
PD_DR
Port D Data Register
XX
R/W
55
00A3
PD_DDR
Port D Data Direction Register
FF
R/W
55
00A4
PD_ALT1
Port D Alternate Register 1
00
R/W
56
00A5
PD_ALT2
Port D Alternate Register 2
00
R/W
56
00A6
PA_ALT0
Port A Alternate Register 0
00
W
56
00A7
PB_ALT0
Port B Alternate Register 0
00
W
56
Chip Select/Wait State Generator
00A8
CS0_LBR
Chip Select 0 Lower Bound Register
00
R/W
85
00A9
CS0_UBR
Chip Select 0 Upper Bound Register
FF
R/W
86
00AA
CS0_CTL
Chip Select 0 Control Register
E8
R/W
87
00AB
CS1_LBR
Chip Select 1 Lower Bound Register
00
R/W
85
00AC
CS1_UBR
Chip Select 1 Upper Bound Register
00
R/W
86
00AD
CS1_CTL
Chip Select 1 Control Register
00
R/W
87
00AE
CS2_LBR
Chip Select 2 Lower Bound Register
00
R/W
85
00AF
CS2_UBR
Chip Select 2 Upper Bound Register
00
R/W
86
00B0
CS2_CTL
Chip Select 2 Control Register
00
R/W
87
00B1
CS3_LBR
Chip Select 3 Lower Bound Register
00
R/W
85
00B2
CS3_UBR
Chip Select 3 Upper Bound Register
00
R/W
86
00B3
CS3_CTL
Chip Select 3 Control Register
00
R/W
87
Random Access Memory Control
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
35
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
00B4
RAM_CTL
RAM Control Register
C0
R/W
94
00B5
RAM_ADDR_U
RAM Address Upper Byte Register
FF
R/W
95
00B6
MBIST_GPR
General-Purpose RAM MBIST Control
00
R/W
96
00B7
MBIST_EMR
Ethernet MAC RAM MBIST Control
00
R/W
96
Serial Peripheral Interface
00B8
SPI_BRG_L
SPI Baud Rate Generator 
Register—Low Byte
02
R/W
207
00B9
SPI_BRG_H
SPI Baud Rate Generator 
Register—High Byte
00
R/W
207
00BA
SPI_CTL
SPI Control Register
04
R/W
208
00BB
SPI_SR
SPI Status Register
00
R
209
00BC
SPI_TSR
SPI Transmit Shift Register
XX
W
210
SPI_RBR
SPI Receive Buffer Register
XX
R
210
Infrared Encoder/Decoder Control
00
R/W
199
Infrared Encoder/Decoder
00BF
IR_CTL
Universal Asynchronous Receiver/Transmitter 0 (UART0)
00C0
00C1
00C2
UART0_RBR
UART 0 Receive Buffer Register
XX
R
184
UART0_THR
UART 0 Transmit Holding Register
XX
W
184
UART0_BRG_L
UART 0 Baud Rate Generator
Register—Low Byte
02
R/W
182
UART0_IER
UART 0 Interrupt Enable Register
00
R/W
185
UART0_BRG_H
UART 0 Baud Rate Generator
Register—High Byte
00
R/W
183
UART0_IIR
UART 0 Interrupt Identification Register
01
R
186
UART0_FCTL
UART 0 FIFO Control Register
00
W
187
Universal Asynchronous Receiver/Transmitter 0 (UART0)
00C3
UART0_LCTL
UART 0 Line Control Register
00
R/W
188
00C4
UART0_MCTL
UART 0 Modem Control Register
00
R/W
190
00C5
UART0_LSR
UART 0 Line Status Register
60
R
191
00C6
UART0_MSR
UART 0 Modem Status Register
XX
R
193
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
36
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
00C7
UART0_SPR
UART 0 Scratch Pad Register
00
R/W
194
I2C_SAR
I2C Slave Address Register
00
R/W
224
I2C
00C8
2
00C9
I2C_XSAR
I C Extended Slave Address Register
00
R/W
224
00CA
I2C_DR
I2C Data Register
00
R/W
225
00
R/W
226
00CB
I2C_CTL
2
I C Control Register
General-Purpose Input/Output Ports
00CE
PC_ALT0
Port C Alternate Register 0
00
W
56
00CF
PD_ALT0
Port D Alternate Register 0
00
W
56
00CC
00CD
2
I2C_SR
I C Status Register
F8
R
227
I2C_CCR
I2C Clock Control Register
00
W
229
XX
W
230
I2C_SRR
2
I C Software Reset Register
Universal Asynchronous Receiver/Transmitter 1 (UART1)
00D0
00D1
00D2
00D3
UART1_RBR
UART 1 Receive Buffer Register
XX
R
184
UART1_THR
UART 1 Transmit Holding Register
XX
W
184
UART1_BRG_L
UART 1 Baud Rate Generator
Register—Low Byte
02
R/W
182
UART1_IER
UART 1 Interrupt Enable Register
00
R/W
185
UART1_BRG_H
UART 1 Baud Rate Generator
Register—High Byte
00
R/W
183
UART1_IIR
UART 1 Interrupt Identification Register
01
R
186
UART1_FCTL
UART 1 FIFO Control Register
00
W
187
UART1_LCTL
UART 1 Line Control Register
00
R/W
188
Universal Asynchronous Receiver/Transmitter 0 (UART0)
00D4
UART1_MCTL
UART 1 Modem Control Register
00
R/W
190
00D5
UART1_LSR
UART 1 Line Status Register
60
R/W
191
00D6
UART1_MSR
UART 1 Modem Status Register
XX
R/W
193
00D7
UART1_SPR
UART 1 Scratch Pad Register
00
R/W
194
Low-Power Control
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
37
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
00DB
CLK_PPD1
Clock Peripheral Power-Down 
Register 1
00
R/W
47
00DC
CLK_PPD2
Clock Peripheral Power-Down
Register 2
00
R/W
48
Real-Time Clock
00E0
RTC_SEC
RTC Seconds Register
XX
R/W
161
00E1
RTC_MIN
RTC Minutes Register
XX
R/W
162
00E2
RTC_HRS
RTC Hours Register
XX
R/W
163
00E3
RTC_DOW
RTC Day-of-the-Week Register
0X
R/W
164
00E4
RTC_DOM
RTC Day-of-the-Month Register
XX
R/W
165
00E5
RTC_MON
RTC Month Register
XX
R/W
166
00E6
RTC_YR
RTC Year Register
XX
R/W
167
00E7
RTC_CEN
RTC Century Register
XX
R/W
168
00E8
RTC_ASEC
RTC Alarm Seconds Register
XX
R/W
169
00E9
RTC_AMIN
RTC Alarm Minutes Register
XX
R/W
170
00EA
RTC_AHRS
RTC Alarm Hours Register
XX
R/W
171
00EB
RTC_ADOW
RTC Alarm Day-of-the-Week Register
0X
R/W
172
00EC
RTC_ACTRL
RTC Alarm Control Register
00
R/W
173
00ED
RTC_CTRL
RTC Control Register
x0xxxx00
b/
x0xxxx10
b4
R/W
174
Chip Select Bus Mode Control
00F0
CS0_BMC
Chip Select 0 Bus Mode Control
Register
02
R/W
88
00F1
CS1_BMC
Chip Select 1 Bus Mode Control
Register
02
R/W
88
00F2
CS2_BMC
Chip Select 2 Bus Mode Control
Register
02
R/W
88
00F3
CS3_BMC
Chip Select 3 Bus Mode Control
Register
02
R/W
88
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
38
Table 3. Register Map (Continued)
Address
(hex)
Mnemonic
Name
Reset
(hex)
CPU
Access
Page
No
Flash Memory Control
00F5
FLASH_KEY
Flash Key Register
00
W
102
00F6
FLASH_DATA
Flash Data Register
XX
R/W
103
00F7
FLASH_ADDR_U
Flash Address Upper Byte Register
00
R/W
104
00F8
FLASH_CTL
Flash Control Register
88
R/W
105
00F9
FLASH_FDIV
Flash Frequency Divider Register
01
R/W
106
00FA
FLASH_PROT
Flash Write/Erase Protection Register
FF
R/W
107
00FB
FLASH_IRQ
Flash Interrupt Control Register
00
R/W
108
00FC
FLASH_PAGE
Flash Page Select Register
00
R/W
109
00FD
FLASH_ROW
Flash Row Select Register
00
R/W
111
00FE
FLASH_COL
Flash Column Select Register
00
R/W
112
00FF
FLASH_PGCTL
Flash Program Control Register
00
R/W
112
PS019215-0910
Register Map
eZ80F91 MCU
Product Specification
39
eZ80® CPU Core
The eZ80® CPU is the first 8-bit CPU to support 16 MB linear addressing. Each software
module or task under a real-time executive or operating system operates in Z80®
compatible (64 KB) mode or full 24-bit (16 MB) address mode.
The CPU instruction set is a superset of the instruction sets for the Z80 and Z180 CPUs.
Z80 and Z180 programs are executed on an eZ80 CPU with little or no modification.
Features
The features of eZ80 CPU include:
•
•
•
•
•
•
•
•
Code-compatible with Z80 and Z180 products
24-bit linear address space
Single-cycle instruction fetch
Pipelined fetch, decode, and execute
Dual Stack Pointers for ADL (24-bit) and Z80 (16-bit) memory modes
24-bit CPU registers and Arithmetic Logic Unit (ALU)
Debug support
Nonmaskable Interrupt (NMI), plus support for 128 maskable vectored interrupts
New Instructions
The new instructions are listed below:
•
Loads/unloads the I register with a 16-bit value. These new instructions are:
– LD I,HL (ED C7)
– LD HL,I (ED D7)
For more information on the CPU, its instruction set, and eZ80 programming, refer to
eZ80 CPU User Manual (UM0077), available on www.zilog.com.
PS019215-0910
eZ80® CPU Core
eZ80F91 MCU
Product Specification
40
PS019215-0910
eZ80® CPU Core
eZ80F91 MCU
Product Specification
41
Reset
The Reset controller within the eZ80F91 device features a consistent reset function for all
types of resets that affects the system. A system reset, referred in this document as RESET,
returns the eZ80F91 to a defined state. All internal registers affected by a RESET return to
their default conditions. RESET configures the GPIO port pins as inputs and clears the
CPU’s Program Counter to 000000h. Program code execution ceases during RESET.
The events that cause a RESET are:
•
•
•
•
•
•
Power-on reset (POR).
Low-Voltage Brownout (VBO).
External RESET pin assertion.
Watchdog Timer (WDT) time-out when configured to generate a RESET.
Real-Time Clock alarm with the CPU in low-power SLEEP mode.
Execution of a Debug RESET command.
During RESET, an internal RESET mode timer holds the system in RESET for 1025
system clock (SCLK) cycles to allow sufficient time for the primary crystal oscillator to
stabilize. For internal RESET sources, the RESET mode timer begins incrementing on the
next rising edge of SCLK following deactivation of the signal that is initiating the RESET
event. For external RESET pin assertion, the RESET mode timer begins on the next rising
edge of SCLK following assertion of the RESET pin for three consecutive SCLK cycles.
Note:
The default clock source for SCLK on RESET is the crystal input (XIN). See the CLK_MUX
values in the PLL Control Register 0, (see Table 154 on page 269).
External Reset Input and Indicator
The eZ80F91 RESET pin functions as both open-drain (active Low) RESET mode indicator and active Low RESET input. When a RESET event occurs, the internal circuitry
begins driving the RESET pin Low. The RESET pin is held Low by the internal circuitry
until the internal RESET mode timer times out. If the external reset signal is released prior
to the end of the 1025 count time-out, program execution begins following the RESET
mode time-out. If the external reset signal is released after the end of the 1025 count timeout, then program execution begins following release of the RESET input (the RESET pin
is High for four consecutive SCLK cycles).
PS019215-0910
Reset
eZ80F91 MCU
Product Specification
42
Power-On Reset
A POR occurs every time the supply voltage to the part rises from below the Voltage
Brownout threshold (VVBO) to above the POR voltage threshold (VPOR). The internal
bandgap-referenced voltage detector sends a continuous RESET signal to the Reset controller until the supply voltage (VCC) exceeds the POR voltage threshold. After VCC rises
above VPOR, an on-chip analog delay element briefly maintains the RESET signal to the
Reset controller. After this analog delay element times out, the Reset controller holds the
eZ80F91 in RESET until the RESET mode timer expires. POR operation is displayed in
Figure 3. The signals in Figure 3 are not drawn to scale but for displaying purposes only.
VCC = 3.3V
VPOR
VVBO
Program Execution
VCC = 0.0V
System Clock
Oscillator
Startup
Internal RESET
Signal
T ANA
RESET mode timer delay
Figure 3. Power-On Reset Operation
Voltage Brownout Reset
If the supply voltage (VCC) drops below the VVBO after program execution begins, the
eZ80F91 device resets. The VBO protection circuitry detects the low supply voltage and
initiates a RESET via the Reset controller. The eZ80F91 remains in RESET until the supply voltage again returns above the POR voltage threshold (VPOR) and the Reset controller
releases the internal RESET signal. The VBO circuitry rejects short negative brown-out
pulses to prevent spurious RESET events.
VBO operation is displayed in Figure 4 on page 43. The signals in the figure are not drawn
to scale but for illustration purposes only.
PS019215-0910
Reset
eZ80F91 MCU
Product Specification
43
VCC = 3.3V
VPOR
VVBO
VCC = 3.3V
Program Execution
Voltage
Brown-out
Program Execution
System Clock
Internal RESET
Signal
TANA
RESET mode
timer delay
Figure 4. Voltage Brownout Reset Operation
PS019215-0910
Reset
eZ80F91 MCU
Product Specification
44
PS019215-0910
Reset
eZ80F91 MCU
Product Specification
45
Low-Power Modes
The eZ80F91 device provides a range of power-saving features. The highest level of
power reduction is provided by SLEEP mode with all peripherals disabled, including
VBO. The next level of power reduction is provided by the HALT instruction. The most
basic level of power reduction is provided by the clock peripheral power-down registers.
SLEEP Mode
Execution of the CPU’s SLP instruction puts the eZ80F91 device into SLEEP mode. In
SLEEP mode, the operating characteristics are:
•
•
•
•
•
The primary crystal oscillator is disabled.
The system clock is disabled.
The CPU is idle.
The Program Counter (PC) stops incrementing.
The 32 kHz crystal oscillator continues to operate and drives the real-time clock and
WDT (if WDT is configured to operate from the 32 kHz oscillator).
The CPU is brought out of SLEEP mode by any of the following operations:
•
•
•
A RESET via the external RESET pin driven Low.
•
•
A RESET via execution of a Debug RESET command.
A RESET via a real-time clock alarm.
A RESET via a WDT time-out (if running out of the 32 kHz oscillator and configured
to generate a RESET on time-out).
A RESET via the Low-Voltage Brownout (VBO) detection circuit, if enabled.
After exiting SLEEP mode, the standard RESET delay occurs to allow the primary crystal
oscillator to stabilize. For more information, see Figure 4 on page 43.
HALT Mode
Execution of the CPU’s HALT instruction puts the eZ80F91 device into HALT mode. 
In HALT mode, the operating characteristics are:
•
•
•
PS019215-0910
The primary crystal oscillator is enabled and continues to operate.
The system clock is enabled and continues to operate.
The CPU is idle.
Low-Power Modes
eZ80F91 MCU
Product Specification
46
•
The PC stops incrementing.
The CPU is brought out of HALT mode by any of the following operations:
•
•
•
•
A nonmaskable interrupt (NMI).
•
•
A RESET via execution of a Debug RESET command.
A maskable interrupt.
A RESET via the external RESET pin driven Low.
A Watchdog Timer time-out (if, configured to generate either an NMI or RESET upon
time-out).
A RESET via the Low-Voltage Brownout detection circuit, if enabled.
To minimize current in HALT mode, the system clock must be gated-off for all unused 
on-chip peripherals via the Clock Peripheral Power-Down Registers.
HALT Mode and the EMAC Function
When the CPU is in HALT mode, the eZ80F91 device’s EMAC block cannot be disabled
as other peripherals can. On receipt of an Ethernet packet, a maskable Receive interrupt is
generated by the EMAC block, just as it would be in a non-halt mode. Accordingly, the
processor wakes up and continues with the user-defined application.
Clock Peripheral Power-Down Registers
To reduce power, the Clock Peripheral Power-Down Registers allow the system clock to
be blocked to unused on-chip peripherals. On RESET, all peripherals are enabled. The
clock to unused peripherals are gated off by setting the appropriate bit in the Clock Peripheral Power-Down Registers to 1. When powered down, the peripherals are completely disabled. To re-enable, the bit in the Clock Peripheral Power-Down Registers must be cleared
to 0.
Additionally, the VBO_OFF bit of CLK_PPD2 is used to disable the VBO detection circuit and thereby significantly reduce DC current consumption (see Table 234 on page 341)
when this function is not required.
Many peripherals features separate enable/disable control bits that must be appropriately
set for operation. These peripheral specific enable/disable bits do not provide the same
level of power reduction as the Clock Peripheral Power-Down Registers. When powered
down, the individual peripheral control register is not accessible for Read or Write access,
(see Table 4 on page 47 and Table 5 on page 48).
PS019215-0910
Low-Power Modes
eZ80F91 MCU
Product Specification
47
Table 4. Clock Peripheral Power-Down Register 1 (CLK_PPD1 = 00DBh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit Position
Value Description
7
GPIO_D_OFF
1
System clock to GPIO Port D is powered down.
Port D alternate functions do not operate correctly.
0
System clock to GPIO Port D is powered up.
1
System clock to GPIO Port C is powered down.
Port C alternate functions do not operate correctly.
0
System clock to GPIO Port C is powered up.
1
System clock to GPIO Port B is powered down.
Port B alternate functions do not operate correctly.
0
System clock to GPIO Port B is powered up.
1
System clock to GPIO Port A is powered down.
Port A alternate functions do not operate correctly.
0
System clock to GPIO Port A is powered up.
3
SPI_OFF
1
System clock to SPI is powered down.
0
System clock to SPI is powered up.
2
I2C_OFF
1
System clock to I2C is powered down.
0
System clock to I2C is powered up.
1
UART1_OFF
1
System clock to UART1 is powered down.
0
System clock to UART1 is powered up.
0
UART0_OFF
1
System clock to UART0 and IrDA endec is powered down.
0
System clock to UART0 and IrDA endec is powered up.
6
GPIO_C_OFF
5
GPIO_B_OFF
4
GPIO_A_OFF
PS019215-0910
Low-Power Modes
eZ80F91 MCU
Product Specification
48
Table 5. Clock Peripheral Power-Down Register 2 (CLK_PPD2 = 00DCh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R
R
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read Only; R/W = Read/Write.
Bit Position
Value Description
7
PHI_OFF
1
PHI Clock output is disabled (output is high-impedance).
0
PHI Clock output is enabled.
6 VBO_OFF
1
Voltage Brownout detection circuit is disabled. This reduces
DC current consumption in situations where VBO detection is
not necessary. Power-On Reset functionality is not affected by
this setting.
0
VBO detection circuit is enabled.
[5:4]
000
Reserved.
3
TIMER3_OFF
1
System clock to TIMER3 is powered down.
0
System clock to TIMER3 is powered up.
2
TIMER2_OFF
1
System clock to TIMER2 is powered down.
0
System clock to TIMER2 is powered up.
1
TIMER1_OFF
1
System clock to TIMER1 is powered down.
0
System clock to TIMER1 is powered up.
0
TIMER0_OFF
1
System clock to TIMER0 is powered down.
0
System clock to TIMER0 is powered up.
PS019215-0910
Low-Power Modes
eZ80F91 MCU
Product Specification
49
General-Purpose Input/Output
The eZ80F91 device features 32 General-Purpose Input/Output (GPIO) pins. The GPIO
pins are assembled as four 8-bit ports—Port A, Port B, Port C, and Port D. All port signals
are configured as either inputs or outputs. In addition, all the port pins are used as vectored
interrupt sources for the CPU.
The eZ80F91 microcontroller’s GPIO ports are slightly different from its eZ80®
predecessors. Specifically, Port A pins source 8 mA and sink 10 mA. In addition, the 
Port B and C inputs now feature Schmitt-trigger input buffers.
GPIO Operation
GPIO operation is the same for all four GPIO ports (Ports A, B, C, and D). Each port
features eight GPIO port pins. The operating mode for each pin is controlled by four bits
that are divided between four 8-bit registers. The GPIO mode control registers are:
•
•
•
•
Port x Data Register (Px_DR)
Port x Data Direction Register (Px_DDR)
Port x Alternate Register 1 (Px_ALT1)
Port x Alternate Register 2 (Px_ALT2)
where x can be A, B, C, or D representing any of the four GPIO ports. The mode for each
pin is controlled by setting each register bit pertinent to the pin to be configured. For
example, the operating mode for port B pin 7 (PB7) is set by the values contained in
PB_DR[7], PB_DDR[7], PB_ALT1[7], and PB_ALT2[7].
The combination of the GPIO control register bits allows individual configuration of each
port pin for nine modes. In all modes, reading of the Port x Data register returns the
sampled state or level of the signal on the corresponding pin. Table 6 on page 50 lists the
function of each port signal based on these four register bits. After a RESET event, all
GPIO port pins are configured as standard digital inputs with the interrupts disabled.
In addition to the four mode control registers, each port has an 8-bit register, which is used
for clearing edge triggered interrupts. This register is the Port x Alternate register
0(Px_ALT0) where x can be A, B, C, or D representing the four GPIO ports. When a
GPIO pin is configured as an edge triggered interrupt, writing 1 to the corresponding bit of
the Px_ALT0 register clears the interrupt.
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
50
Table 6. GPIO Mode Selection
GPIO Px_ALT2 Px_ALT1 Px_DDR Px_DR
Mode Bits7:0 Bits7:0 Bits7:0 Bits7:0 Port Mode
Output
0
0
0
0
Output
0
0
0
0
1
Output
1
0
0
1
0
Input from pin
High impedance
0
0
1
1
Input from pin
High impedance
0
1
0
0
Open-drain output
0
0
1
0
1
Open-drain I/O
High impedance
0
1
1
0
Open-source I/O
High impedance
0
1
1
1
Open-source output
1
5
1
0
0
0
Reserved
High impedance
6
1
0
0
1
Interrupt—dual edge-triggered
High impedance
1
0
1
0
Alternate function controls port I/O.
1
0
1
1
Alternate function controls port I/O.
1
1
0
0
Interrupt—active Low
High impedance
1
1
0
1
Interrupt—active High
High impedance
1
1
1
0
Interrupt—falling edge-triggered
High impedance
1
1
1
1
Interrupt—rising edge-triggered
High impedance
1
2
3
4
7
8
9
Figure 5 on page 53 and Figure 6 on page 53 display the simplified block diagrams of the
GPIO port pin for the various modes.
GPIO Mode 1—Output
The port pin is configured as a standard digital output pin. The value written to the Port x
Data register (Px_DR) is driven on the pin.
GPIO Mode 2—Input
The port pin is configured as a standard digital input pin. The output is high impedance.
The value stored in the Port x Data register produces no effect. As in all modes, a read
from the Port x Data register returns the pin’s value. GPIO mode 2 is the default operating
mode following a RESET.
GPIO Mode 3—Open Drain
The port pin is configured as open-drain Input/Output. The GPIO pins do not feature an
internal pull-up to the supply voltage. To employ the GPIO pin in OPEN-DRAIN mode,
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
51
an external pull-up resistor must connect the pin to the supply voltage. Writing 0 to the
Port x Data register outputs a Low at the pin. Writing 1 to the Port x Data register results in
high-impedance output.
GPIO Mode 4—Open Source
The port pin is configured as open-source I/O. The GPIO pins do not feature an internal
pull-down to the supply ground. To employ the GPIO pin in OPEN-SOURCE mode, an
external pull-down resistor must connect the pin to the supply ground. Writing 1 to the
Port x Data register outputs a High at the pin. Writing 0 to the Port x Data register results
in a high-impedance output.
GPIO Mode 5—Reserved
This mode produces a high-impedance output.
GPIO Mode 6—Dual Edge Triggered
The port pin is configured for dual edge-triggered interrupt mode. Both a rising and a
falling edge on this pin cause an interrupt request to be sent to the CPU. To select this
mode from the default mode (mode 2), you must:
1. Set Px_DR=1
2. Set Px_ALT2=1
3. Set Px_ALT1=0
4. Set Px_DDR=0
Writing a 1 to the Port x ALT0 register bit position corresponding to the interrupt request
clears the interrupt.
GPIO Mode 7—Alternate Functions
The port pin is configured to pass control over to the alternate (secondary) functions
assigned to the pin. For example, the alternate mode function for PC5 is the DSR1 input
signal to UART1 and the alternate mode function for PB4 is the timer 3 input capture.
When GPIO mode 7 is enabled, the pin output data and pin high-impedance control is
obtained from the alternate function's data output and high-impedance control,
respectively. The value in the Port x Data register produces no effect on operation. Input
signals are sampled by the system clock before being passed to the alternate input
function.
If the alternate function of a pin is an input and alternate function mode for that pin is not
enabled, the input is driven to a default non-asserted value. For example, in alternate mode
function, PC5 drives the DSR1 signal to UART1. As this signal is Low level true, the
DSR1 signal to UART1 is driven to 1 when PC5 is not in alternate mode function.
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
52
GPIO Mode 8—Level Sensitive Interrupt
The port pin is configured for level-sensitive interrupt mode. The value in the Port x Data
register determines if a low or high-level causes an interrupt request. An interrupt request
is generated when the level at the pin is the same as the level stored in the Port x Data
register. The port pin value is sampled by the system clock. The input pin must be held at
the selected interrupt level for a minimum of two system clock periods to initiate an
interrupt. The interrupt request remains active as long as this condition is maintained at the
external source. For example, if a port pin is configured as a low-level-sensitive interrupt,
the interrupt request will be asserted when the pin has been low for two system clocks and
remains active until the pin goes high.
Configuring a pin for mode 8 requires a transition through mode 9 (edge triggered mode).
To avoid the possibility of an unwanted interrupt while transition through mode 9, the
following steps must be taken to select mode 8 when starting from the default mode (mode
2):
1. Disable interrupts
2. Set Px_DR = 0 (low level interrupt) or 1 (high level interrupt)
3. Set Px_ALT2 = 1
4. Set Px_ALT1 =1 (mode 9)
5. Set Px_DDR = 0 (mode 8)
6. Set Px_ALT0 = 1 (to clear possible mode 9 interrupt)
7. Enable interrupts
GPIO Mode 9—Edge Triggered Interrupt
The port pin is configured for single edge triggered interrupt mode. The value in the Port x
Data register determines whether a positive or negative edge causes an interrupt request.
Writing 0 to the Port x Data register bit sets the selected pin to generate an interrupt
request for falling edges. Writing 1 to the Port x Data register bit sets the selected pin to
generate an interrupt request for rising edges. The interrupt request remains active until 1
is written to the corresponding bit of the Port x Alternate register 0. To select mode 9 from
the default mode (mode 2), you must:
1. Set the Port x Data register
2. Set Px_ALT2 = 1
3. Set Px_ALT1 = 1
4. Set Px_DDR=1
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
53
Simplified GPIO Port Block Diagram for Modes 2, 6, 7(input), 8, and 9
GPIO Port Pin
Mode 2
Mode 6
Mode 8
Mode 9
Mode 7(Input)
GPIO Output Buffer
Px_DR*
ENB
D
Q
D
Input to chip
Q
Tristated for
modes 2,6,8,9
and 7(Input) SysClock
Alternate
Function
Input
Default Value
Mode 7(Input)
Interrupt Interrupt
Logic
Clear Interrupt
Modes 6,8,9
* Reading from the Px_DR returns
the value stored in this register
Figure 5. GPIO Port Pin Block Diagram for Input and Interrupt Modes
Simplified GPIO Port Block Diagram for Modes 1, 3, 4, and 7 (Output)
VDD
Px_DR*
Data
System Clock
D
Mode 4
Q
Q
GPIO Output Buffer
Mode 3
Mode 1
Mode 7 (Output)
ENB
GPIO Port
Pin
External
Pull-up resistor
required for
Mode 3
(open drain)
External Pull-down resistor
required for Mode 4
(Open source)
Alternate Function Output
* Writing to the Px_DR stores
the value in this register
Figure 6. GPIO Port Pin Block Diagram for Output and Input/Output Mode
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
54
GPIO Interrupts
Each port pin is used as an interrupt source. Interrupts are either level- or edge-triggered.
Level-Triggered Interrupts
When the port is configured for level-triggered interrupts (mode 8), the corresponding port
pin is open-drain. An interrupt request is generated when the level at the pin is the same as
the level stored in the Port x Data register. The port pin value is sampled by the system
clock. The input pin must be held at the selected interrupt level for a minimum of two
clock periods to initiate an interrupt. The interrupt request remains active as long as this
condition is maintained at the external source.
For example, if PA3 is programmed for low-level interrupt and the pin is forced Low for
two clock cycles, an interrupt request signal is generated from that port pin and sent to the
CPU. The interrupt request signal remains active until the external device driving PA3
forces the pin high. The CPU must be enabled to respond to interrupts for the interrupt
request signal to be acted upon.
Edge Triggered Interrupts
When the port is configured for edge triggered interrupts, the corresponding port pin is
open-drain. If the pin receives the correct edge from an external device, the port pin
generates an interrupt request signal to the CPU.
When configured for dual-edge triggered interrupt mode (GPIO mode 6), both a rising and
a falling edge on the pin cause an interrupt request to be sent to the CPU. To select mode 6
from the default mode (mode 2), you must:
1. Set Px_DR = 1
2. Set Px_ALT2 =1
3. Set Px_ALT1= 0
4. Set Px_DDR = 0
When configured for single-edge triggered interrupt mode (GPIO mode 9), the value in
the Port x Data register determines whether a positive or negative edge causes an interrupt
request. 0 in the Port x Data register bit sets the selected pin to generate an interrupt
request for falling edges. 1 in the Port x Data register bit sets the selected pin to generate
an interrupt request for rising edges. To select mode 9 from the default mode (mode 2),
you must:
1. Set Px_DR = 1
2. Set Px_ALT2 = 1
3. Set Px_ALT = 1
4. Set Px_DDR = 1
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
55
Edge triggered interrupts are cleared by writing 1 to the corresponding bit of the Px_ALT0
register. For example, if PD4 has been set up to generate an edge triggered interrupt, the
interrupt is cleared by writing a 1 to Px_ALT0[4].
GPIO Control Registers
Each GPIO port has four registers that controls its operation. The operating mode of each
bit within a port is selected by writing to the corresponding bits of these four registers as
listed in Table 6 on page 50. These four registers are Port Data register (Px_DR), Port Data
Direction register (Px_DDR), Port Alternate register 1 (PX_ALT1), and Port Alternate
register 2 (Px_ALT2). In addition to these four control registers, each port has a Port
Alternate register 0 (Px_ALT0), which is used for clearing edge triggered interrupts.
Port x Data Registers
When the port pins are configured for one of the output modes, the data written to the 
Port x Data registers (see Table 7) is driven on the corresponding pins. In all modes,
reading from the Port x Data registers always returns the sampled current value of the
corresponding pins. When the port pins are configured for edge triggered interrupts or
level-sensitive interrupts, the value written to the Port x Data register bit selects the
interrupt edge or interrupt level (for more details on GPIO mode selection, see Table 6 on
page 50).
Table 7. Port x Data Registers
(PA_DR = 0096h, PB_DR = 009Ah, PC_DR = 009Eh, PD_DR = 00A2h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: X = Undefined; R/W = Read/Write.
Port x Data Direction Registers
In conjunction with the other GPIO Control registers, the Port x Data Direction registers
(see Table 8) control the operating modes of the GPIO port pins. For more details on GPIO
mode selection, see Table 6 on page 50.
Table 8. Port x Data Direction Registers
(PA_DDR = 0097h, PB_DDR = 009Bh, PC_DDR = 009Fh, PD_DDR = 00A3h)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
1
1
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
56
Port x Alternate Register 0
The Port x Alternate register 0 is used to clear edge triggered interrupts. If an edge
triggered interrupt occurs, writing 1 to the corresponding bit of this register will clear it.
Table 9. Port x Alternate Registers 0
(PA_ALT0 = 00A6h, PB_ALT0 = 00A7h, PC_ALT0 = 00CEh, PD_ALT0 = 00CFh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write only
Port x Alternate Register 1
In conjunction with the other GPIO Control registers, the Port x Alternate Register 1 (see
Table 10) controls the operating modes of the GPIO port pins. For more details on GPIO
mode selection, see Table 6 on page 50.
Table 10. Port x Alternate Registers 1
(PA_ALT1 = 0098h, PB_ALT1 = 009Ch, PC_ALT1 = 00A0h, PD_ALT1 = 00A4h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Port x Alternate Register 2
In conjunction with the other GPIO Control registers, the Port x Alternate Register 2 (see
Table 11) controls the operating modes of the GPIO port pins. For more details on GPIO
mode selection, see Table 6 on page 50.
Table 11. Port x Alternate Registers 2
(PA_ALT2 = 0099h, PB_ALT2 = 009Dh, PC_ALT2 = 00A1h, PD_ALT2 = 00A5h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
PS019215-0910
General-Purpose Input/Output
eZ80F91 MCU
Product Specification
57
Interrupt Controller
The interrupt controller on the eZ80F91 device routes the interrupt request signals from
the internal peripherals, external devices (via the internal port I/O), and the nonmaskable
interrupt (NMI) pin to the CPU.
Maskable Interrupts
On the eZ80F91 device, all maskable interrupts use the CPU’s vectored interrupt function.
The size of I register is modified to 16 bits in the eZ80F91 device differing from the previous versions of eZ80® CPU, to allow for a 16 MB range of interrupt vector table placement. Additionally, the size of the IVECT register is increased from 8 bits to 9 bits to
provide an interrupt vector table that is expanded and more easily integrated with other
interrupts.
The vectors are 4 bytes (32 bits) apart, even though only 3 bytes (24 bits) are required. 
A fourth byte is implemented for both programmability and expansion purposes.
Starting the interrupt vectors at 40h allows for easy implementation of the interrupt controller vectors with the RST vectors. Table 12 lists the interrupt vector sources by priority
for each of the maskable interrupt sources. The maskable interrupt sources are listed in
order of their priority, with vector 40h being the highest-priority interrupt. In ADL mode,
the full 24-bit interrupt vector is located at starting address {I[15:1], IVECT[8:0]}, where
I[15:0] is the CPU’s Interrupt Page Address register.
Table 12. Interrupt Vector Sources by Priority
Priority
Vector
Source
Priority
Vector
Source
0
040h
EMAC Rx
24
0A0h
Port B 0
1
044h
EMAC Tx
25
0A4h
Port B 1
2
048h
EMAC SYS
26
0A8h
Port B 2
3
04Ch
PLL
27
0ACh
Port B 3
4
050h
Flash
28
0B0h
Port B 4
5
054h
Timer 0
29
0B4h
Port B 5
6
058h
Timer 1
30
0B8h
Port B 6
7
05Ch
Timer 2
31
0BCh
Port B 7
8
060h
Timer 3
32
0C0h
Port C 0
9
064h
Unused*
33
0C4h
Port C 1
10
068h
Unused*
34
0C8h
Port C 2
PS019215-0910
Interrupt Controller
eZ80F91 MCU
Product Specification
58
Table 12. Interrupt Vector Sources by Priority (Continued)
Priority
Vector
Source
Priority
Vector
Source
11
06Ch
RTC
35
0CCh
Port C 3
12
070h
UART 0
36
0D0h
Port C 4
13
074h
UART 1
37
0D4h
Port C 5
14
078h
I2 C
38
0D8h
Port C 6
15
07Ch
SPI
39
0DCh
Port C 7
16
080h
Port A 0
40
0E0h
Port D 0
17
084h
Port A 1
41
0E4h
Port D 1
18
088h
Port A 2
42
0E8h
Port D 2
19
08Ch
Port A 3
43
0ECh
Port D 3
20
090h
Port A 4
44
0F0h
Port D 4
21
094h
Port A 5
45
0F4h
Port D 5
22
098h
Port A 6
46
0F8h
Port D 6
23
09Ch
Port A 7
47
0FCh
Port D 7
Note: *The vector addresses 064h and 068h are left unused to avoid conflict with the nonmaskable
interrupt (NMI) address 066h. The NMI is prioritized higher than all maskable interrupts.
The program must store the interrupt service routine starting address in the 
four-byte interrupt vector locations. For example in ADL mode, the three-byte address for
the SPI interrupt service routine is stored at {I[15:1], 07Ch}, {I[15:1], 07Dh}, and {I[15:1],
07Eh}. In Z80® mode, the two-byte address for the SPI interrupt service routine is stored at
{MBASE[7:0], I[7:1], 07Ch} and {MBASE, I[7:1], 07Dh}. The LSB is stored at the lower
address.
When one or more interrupt requests (IRQs) become active, an interrupt request is
generated by the interrupt controller and sent to the CPU. The corresponding 9-bit
interrupt vector for the highest-priority interrupt is placed on the 9-bit interrupt vector bus,
IVECT[8:0]. The interrupt vector bus is internal to the eZ80F91 device and is therefore
externally not visible. The response time of the CPU to an interrupt request is a function of
the current instruction being executed as well as the number of wait states being asserted.
The interrupt vector, {I[15:1], IVECT[8:0]} is visible on the address bus (ADDR[23:0]),
when the interrupt service routine begins. The response of the CPU to a vectored interrupt
on the eZ80F91 device is listed in Table 13 on page 59. Interrupt sources are required to be
active until the Interrupt Service Routine (ISR) starts.
Note:
PS019215-0910
The lower bit of the I register is replaced with the MSB of the IVECT from the interrupt controller. As a result, the interrupt vector table is required to be placed onto a 512-byte
Interrupt Controller
eZ80F91 MCU
Product Specification
59
boundary. Setting the LSB of the I register produces no effect on the interrupt vector
address.
Table 13. Vectored Interrupt Operation
Memory
Mode
ADL
Bit
MADL
Bit
Operation
Z80® Mode 0
0
Read the LSB of the interrupt vector placed on the internal vectored interrupt
bus, IVECT [8:0], by the interrupting peripheral.
IEF1  0
IEF2  0
The Starting Program Counter is effective {MBASE, PC[15:0]}.
Push the 2-byte return address PC[15:0] onto the ({MBASE,SPS}) stack.
The ADL mode bit remains cleared to 0.
The interrupt vector address is located at { MBASE, I[7:1], IVECT[8:0] }.
PC[23:0]  ( { MBASE, I[7:1], IVECT[8:0] } ).
The interrupt service routine must end with RETI.
ADL Mode
1
0
Read the LSB of the interrupt vector placed on the internal vectored interrupt
bus, IVECT [8:0], by the interrupting peripheral.
IEF1  0
IEF2  0
The Starting Program Counter is PC[23:0].
Push the 3-byte return address, PC[23:0], onto the SPL stack.
The ADL mode bit remains set to 1.
The interrupt vector address is located at { I[15:1], IVECT[8:0] }.
PC[23:0]  ( { I[15:1], IVECT[8:0] } ).
The interrupt service routine must end with RETI.
Z80 Mode
0
1
Read the LSB of the interrupt vector placed on the internal vectored interrupt
bus, IVECT[8:0], bus by the interrupting peripheral.
• IEF1  0
• IEF2  0
• The Starting Program Counter is effective {MBASE, PC[15:0]}.
• Push the 2-byte return address, PC[15:0], onto the SPL stack.
• Push a 00h byte onto the SPL stack to indicate an interrupt from Z80 mode
(because ADL = 0).
• Set the ADL mode bit to 1.
• The interrupt vector address is located at { I[15:1], IVECT[8:0] }.
• PC[23:0]  ( { I[15:1], IVECT[8:0] } ).
• The interrupt service routine must end with RETI.L
PS019215-0910
Interrupt Controller
eZ80F91 MCU
Product Specification
60
Table 13. Vectored Interrupt Operation (Continued)
Memory
Mode
ADL
Bit
MADL
Bit
Operation
ADL Mode
1
1
Read the LSB of the interrupt vector placed on the internal vectored interrupt
bus, IVECT [8:0], by the interrupting peripheral.
• IEF1  0
• IEF2  0
• The Starting Program Counter is PC[23:0].
• Push the 3-byte return address, PC[23:0], onto the SPL stack.
• Push a 01h byte onto the SPL stack to indicate a restart from ADL mode
(because ADL = 1).
• The ADL mode bit remains set to 1.
• The interrupt vector address is located at {I[15:1], IVECT[8:0]}.
• PC[23:0]  ( { I[15:1], IVECT[8:0] } ).
• The interrupt service routine must end with RETI.L
Interrupt Priority Registers
The eZ80F91 provides two interrupt priority levels for the maskable interrupts. The default
priority (or Level 0) is listed in Table 14 on page 61. The default priority of any maskable
interrupt increases to Level 1 (a higher priority than any Level 0 interrupt) by setting the
appropriate bit in the Interrupt Priority registers as listed in Table 14 on page 61.
PS019215-0910
Interrupt Controller
eZ80F91 MCU
Product Specification
61
Table 14. Interrupt Priority Registers (INT_P0 = 0010h, INT_P1 = 0011h, INT_P2 = 0012h, INT_P3
= 0013h, INT_P4 = 0014h, INT_P5 = 0015h)
Bit
7
6
5
4
3
2
1
0
INT_P0 Reset
0
0
0
0
0
0
0
0
INT_P1 Reset
0
0
0
0
0
0*
0*
0
INT_P2 Reset
0
0
0
0
0
0
0
0
INT_P3 Reset
0
0
0
0
0
0
0
0
INT_P4 Reset
0
0
0
0
0
0
0
0
INT_P5 Reset
0
0
0
0
0
0
0
0
CPU Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Note: X = Undefined; R/W = Read/Write, *Unused.
Bit
Position
Value Description
7
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
6
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
5
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
4
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
3
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
2
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
1
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
0
INT_PX
0
Default Interrupt Priority
1
Level One Interrupt Priority
PS019215-0910
Interrupt Controller
eZ80F91 MCU
Product Specification
62
The Interrupt Vector Priority Control bits are listed in Table 15.
Table 15. Interrupt Vector Priority Control Bits
Priority Control
Bit
Vector
Source
Priority Control
Bit
Vector
Source
INT_P0[0]
040h
EMAC Rx
INT_P3[0]
0A0h
Port B 0
INT_P0[1]
044h
EMAC Tx
INT_P3[1]
0A4h
Port B 1
INT_P0[2]
048h
EMAC SYS
INT_P3[2]
0A8h
Port B 2
INT_P0[3]
04Ch
PLL
INT_P3[3]
0ACh
Port B 3
INT_P0[4]
050h
Flash
INT_P3[4]
0B0h
Port B 4
INT_P0[5]
054h
Timer 0
INT_P3[5]
0B4h
Port B 5
INT_P0[6]
058h
Timer 1
INT_P3[6]
0B8h
Port B 6
INT_P0[7]
05Ch
Timer 2
INT_P3[7]
0BCh
Port B 7
INT_P1[0]
060h
Timer 3
INT_P4[0]
0C0h
Port C 0
INT_P1[1]
064h
Unused*
INT_P4[1]
0C4h
Port C 1
INT_P1[2]
068h
Unused*
INT_P4[2]
0C8h
Port C 2
INT_P1[3]
06Ch
RTC
INT_P4[3]
0CCh
Port C 3
INT_P1[4]
070h
UART 0
INT_P4[4]
0D0h
Port C 4
INT_P1[5]
074h
UART 1
INT_P4[5]
0D4h
Port C 5
INT_P1[6]
078h
I2C
INT_P4[6]
0D8h
Port C 6
INT_P1[7]
07Ch
SPI
INT_P4[7]
0DCh
Port C 7
INT_P2[0]
080h
Port A 0
INT_P5[0]
0E0h
Port D 0
INT_P2[1]
084h
Port A 1
INT_P5[1]
0E4h
Port D 1
INT_P2[2]
088h
Port A 2
INT_P5[2]
0E8h
Port D 2
INT_P2[3]
08Ch
Port A 3
INT_P5[3]
0ECh
Port D 3
INT_P2[4]
090h
Port A 4
INT_P5[4]
0F0h
Port D 4
INT_P2[5]
094h
Port A 5
INT_P5[5]
0F4h
Port D 5
INT_P2[6]
098h
Port A 6
INT_P5[6]
0F8h
Port D 6
INT_P2[7]
09Ch
Port A 7
INT_P5[7]
0FCh
Port D 7
Note: *The vector addresses 064h and 068h are left unused to avoid conflict with the NMI vector address 066h.
If more than one maskable interrupt is prioritized to a higher level (Level 1), the higherpriority interrupts follow the priority order as listed in Table 14 on page 61. For example,
PS019215-0910
Interrupt Controller
eZ80F91 MCU
Product Specification
63
Table 16 lists the maskable interrupts 044h (EMAC Tx), 084h (Port A 1), and 06Ch
(RTC) as elevated to priority Level 1. Table 17 lists the new interrupt priority for the top
ten maskable interrupts.
Table 16. Example: Maskable Interrupt Priority
Priority
Register
Setting
Description
INT_P0
02h
Increase 044h (EMAC Tx) to Priority Level 1
INT_P1
08h
Increase 06Ch (RTC) to Priority Level 1
INT_P2
02h
Increase 084h (Port A1) to Priority Level 1
INT_P3
00h
Default priority
INT_P4
00h
Default priority
INT_P5
00h
Default priority
Table 17. Example: Priority Levels for Maskable Interrupts
PS019215-0910
Priority
Vector
Source
0
044h
EMAC Tx
1
06Ch
RTC
2
084h
Port A 1
3
040h
EMAC Rx
4
048h
EMAC SYS
5
04Ch
PLL
6
050h
Flash
7
054h
Timer 0
8
058h
Timer 1
9
05Ch
Timer 2
Interrupt Controller
eZ80F91 MCU
Product Specification
64
GPIO Port Interrupts
All interrupts are latched. In effect, an interrupt is held even if the interrupt occurs while
another interrupt is being serviced and interrupts are disabled, or if the interrupt is of a
lower priority. However, before the latched ISR completes its task or re-enables interrupts,
the ISR must clear the interrupt. For on-chip peripherals, the interrupt is cleared when the
data register is accessed. For GPIO-level interrupts, the interrupt signal must be removed
before the ISR completes its task. For GPIO-edge interrupts (single and dual), the interrupt
is cleared by writing a 1 to the corresponding bit position in the Px_ALT0 register. See
Edge Triggered Interrupts on page 54.
Note:
For F91 devices with a ZDI or JTAG revision less than 2, care must be taken using a GPIO
data register when it is configured for interrupts. For edge-interrupt modes (modes 6 and
9) as discussed earlier, writing 1 clears the interrupt. However, 1 in the data register also
conveys a particular configuration. For example, when the data register Px_DR is set first
followed by the Px_ALT2, Px_ALT1, and Px_DDR registers, then the configuration is performed correctly. Writing 1 to the register later to clear interrupts does not change the configuration. For F91 devices with a ZDI or JTAG revision 2 or later, the clearing of
interrupts is accomplished through the new Px_ALT0 registers and the above problem does
not exist.

In mode 9 operation, if the GPIO is already configured for mode 9 and if the trigger edge
must be changed (from falling to rising or from rising to falling), then the configuration
must be changed to another mode, such as Mode 2, and then changed back to mode 9. For
example, enter mode 2 by writing the registers in the sequence PxDR, Px_ALT2, Px_ALT1,
and Px_DDR. Next, change back to mode 9 by writing the registers in the sequence PxDR,
Px_ALT2, Px_ALT1, and Px_DDR.
In Mode 8 operation, if the GPIO is configured for level-sensitive interrupts, a Write value
to Px_DR after configuration must be the same Write value used when configuring the
GPIO.
PS019215-0910
Interrupt Controller
eZ80F91 MCU
Product Specification
65
Chip Selects and Wait States
The eZ80F91 generates four chip selects for external devices. Each chip select is programmed to access either the memory space or the I/O space. The memory chip selects are
individually programmed on a 64 KB boundary. Each I/O chip selects choose a 256-byte
section of I/O space. In addition, each chip select is programmed for up to 7 Wait states.
Memory and I/O Chip Selects
Each of the chip selects are enabled either for the memory address space or the I/O address
space, but not both. To select the memory address space for a particular chip select,
CSX_IO (CSx_CTL[4]) must be reset to 0. To select the I/O address space for a particular
chip select, CSX_IO must be set to 1. After RESET, the default is for all chip selects to be
configured for the memory address space. For either the memory address space or the I/O
address space, the individual chip selects must be enabled by setting CSX_EN
(CSx_CTL[3]) to 1.
Memory Chip Select Operation
Operation of each of the memory chip select is controlled by three control registers. To
enable a particular memory chip select, the following conditions must be satisfied:
•
•
•
The chip select is enabled by setting CSx_EN to 1.
•
On-chip Flash is not configured for the same address space, because on-chip Flash is
prioritized higher than all memory chip selects.
•
On-chip RAM is not configured for the same address space, because on-chip RAM is
prioritized higher than Flash and all memory chip selects.
•
•
No higher priority (lower number) chip select meets the above conditions.
The chip select is configured for memory by clearing CSX_IO to 0.
The address is in the associated chip select range:
CSx_LBR[7:0]  ADDR[23:16]  CSx_UBR[7:0].
A memory access instruction must be executing.
If all the preceding conditions are satisfied to generate a memory chip select, then the following results occur:
•
•
•
PS019215-0910
The appropriate chip select—CS0, CS1, CS2, or CS3 is asserted (driven Low).
MREQ is asserted (driven Low).
Depending on the instruction either RD or WR is asserted (driven Low).
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
66
If the upper and lower bounds are set to the same value (CSx_UBR = CSx_LBR), then a
particular chip select is valid for a single 64 KB page.
Memory Chip Select Priority
A lower-numbered chip select is granted priority over a higher-numbered chip select. For
example, if the address space of chip select 0 overlaps the chip select 1 address space, then
chip select 0 is active. If the address range programmed for any chip select signal overlaps
with the address of internal memory, the internal memory is accorded higher priority. If
the particular chip select(s) are configured with an address range that overlaps with an
internal memory address and when the internal memory is accessed, the chip select signal
is not asserted.
Reset States
On RESET, chip select 0 is active for all addresses, because its Lower Bound register
resets to 00h and its Upper Bound register resets to FFh. All the other chip select Lower
and Upper Bound registers reset to 00h.
Memory Chip Select Example
The use of Memory chip selects is displayed in Figure 7 on page 67. The associated control register values are listed in Table 18 on page 67. In this example, all four chip selects
are enabled and configured for memory addresses. Also, CS1 overlaps with CS0. Because
CS0 is prioritized higher than CS1, CS1 is not active for much of its defined address
space.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
67
Memory
Location
CS3_UBR = FFh
FFFFFFh
CS3 Active
3 MB Address Space
CS3_LBR = D0h
CS2_UBR = CFh
CS2 Active
3 MB Address Space
CS2_LBR = A0h
CS1_UBR = 9Fh
CS1 Active
2 MB Address Space
CS0_UBR = 7Fh
D00000h
CFFFFFh
A00000h
9FFFFFh
800000h
7FFFFFh
CS0 Active
8 MB Address Space
CS0_LBR = CS1_LBR = 00h
000000h
Figure 7. Example: Memory Chip Select
Table 18. Example: Register Values for Figure 7 Memory Chip Select
Chip
Select
CSx_CTL[3] CSx_CTL[4]
CSx_EN
CSx_IO
CSx_LBR
CSx_UBR Description
CS0
1
0
00h
7Fh
CS0 is enabled as a Memory chip
select. Valid addresses range from
000000h–7FFFFFh.
CS1
1
0
00h
9Fh
CS1 is enabled as a Memory chip
select. Valid addresses range from
800000h–9FFFFFh.
CS2
1
0
A0h
CFh
CS2 is enabled as a Memory chip
select. Valid addresses range from
A00000h–CFFFFFh.
CS3
1
0
D0h
FFh
CS3 is enabled as a Memory chip
select. Valid addresses range from
D00000h–FFFFFFh.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
68
Input/Output Chip Select Operation
I/O chip selects will be active only when the CPU is performing I/O instructions. Because
the I/O space is separate from the memory space in the eZ80F91 device, a conflict
between I/O and memory addresses never occurs.
The eZ80F91 supports a 16-bit I/O address. The I/O chip select logic decodes the High
byte of the I/O address, ADDR[15:8]. Because the upper byte of the address bus,
ADDR[23:16], is ignored, the I/O devices are always accessed from memory mode (ADL
or Z80®). The MBASE offset value used for setting the Z80 MEMORY mode page is also
always ignored.
Four I/O chip selects are available with the eZ80F91 device. To generate a particular I/O
chip select, the following conditions must be satisfied:
•
•
•
•
•
The chip select is enabled by setting CSx_EN to 1.
The chip select is configured for I/O by setting CSX_IO to 1.
An I/O chip select address match occurs—ADDR[15:8] = CSx_LBR[7:0].
No higher-priority (lower-number) chip select meets the above conditions.
The I/O address is not within the on-chip peripheral address range 0000h–00FFh. 
On-chip peripheral registers assume priority for all addresses where:
0000h  ADDR[15:0]  00FFh
•
An I/O instruction must be executing.
If all of the foregoing conditions are met to generate an I/O chip select, then the following
results occur:
•
•
•
The appropriate chip select—CS0, CS1, CS2, or CS3 is asserted (driven Low).
IORQ is asserted (driven Low).
Depending on the instruction, either RD or WR is asserted (driven Low).
Wait States
For each of the chip selects, programmable Wait states are asserted to provide external
devices with additional clock cycles to complete their Read or Write operations. The
number of wait states for a particular chip select is controlled by the 3-bit field
CSx_WAIT (CSx_CTL[7:5]). The Wait states are independently programmed to provide 0
to 7 Wait states for each chip select. The Wait states idle the CPU for the specified number
of system clock cycles.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
69
WAIT Input Signal
Similar to the programmable wait states, an external peripheral drives the WAIT input pin
to force the CPU to provide additional clock cycles to complete its Read or Write operation. Driving the WAIT pin Low stalls the CPU. The CPU resumes operation on the first
rising edge of the internal system clock following deassertion of the WAIT pin.
Caution: If the WAIT pin is to be driven by an external device, the corresponding chip select for
the device must be programmed to provide at least one wait state. Due to input sampling
of the WAIT input pin (see Figure 8), one programmable wait state is required to allow
the external peripheral sufficient time to assert the WAIT pin. It is recommended that the
corresponding chip select for the external device be programmed to provide the maximum number of wait states (seven).
Wait
Pin
D
Q
eZ80
CPU
System Clock
Figure 8. Wait Input Sampling Block Diagram
An example of wait state operation is illustrated in Figure 9 on page 70. In this example,
the chip select is configured to provide a single wait state. The external peripheral
accessed drives the WAIT pin Low to request assertion of an additional wait state. If the
WAIT pin is asserted for additional system clock cycles, wait states are added until the
WAIT pin is deasserted (active High).
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
70
TCLK
TWAIT
SCLK
ADDR[23:0]
DATA[7:0]
(output)
CSx
MREQ
RD
INSTRD
Figure 9. Example: Wait State Read Operation
Chip Selects During Bus Request/Bus Acknowledge Cycles
When the CPU relinquishes the address bus to an external peripheral in response to an
external bus request (BUSREQ), it drives the bus acknowledge pin (BUSACK) Low. The
external peripheral then drives the address bus (and data bus). The CPU continues to generate chip select signals in response to the address on the bus. External devices cannot
access the internal registers of the eZ80F91.
Bus Mode Controller
The bus mode controller allows the address and data bus timing and signal formats of the
eZ80F91 to be configured to connect with external devices compatible with eZ80®, Z80®,
Intel™ and Motorola microcontrollers. Bus modes for each of the chip selects are configured independently using the Chip Select Bus Mode Control Registers. The number of
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
71
CPU system clock cycles per bus mode state is also independently programmable. For
Intel bus mode, multiplexed address and data are selected in which both the lower byte of
the address and the data byte use the data bus, DATA[7:0]. Each of the bus modes are
explained in the following sections.
eZ80® Bus Mode
Chip selects configured for eZ80 bus mode do not modify the bus signals from the CPU.
The timing diagrams for external Memory and I/O Read and Write operations are shown in
the AC Characteristics on page 344. The default mode for each chip select is eZ80 mode.
Z80® Bus Mode
Chip selects configured for Z80 mode modify the eZ80 bus signals to match the Z80 microprocessor address and data bus interface signal format and timing. During Read operations,
the Z80 Bus mode employs three states—T1, T2, and T3 as listed in Table 19.
Table 19. Z80 Bus Mode Read States
STATE T1
The Read cycle begins in State T1. The CPU drives the address onto the address bus and
the associated chip select signal is asserted.
STATE T2
During State T2, the RD signal is asserted. Depending on the instruction, either the MREQ
or IORQ signal is asserted. If the external WAIT pin is driven Low at least one CPU system
clock cycle prior to the end of State T2, additional Wait states (TWAIT) are asserted until the
WAIT pin is driven High.
STATE T3
During State T3, no bus signals are altered. The data is latched by the eZ80F91 at the rising
edge of the CPU system clock at the end of State T3.
During Write operations, Z80 Bus mode employs three states—T1, T2, and T3 as listed in
Table 20.
Table 20. Z80 Bus Mode Write States
STATE T1
The Write cycle begins in State T1. The CPU drives the address onto the address bus, and
the associated chip select signal is asserted.
STATE T2
During State T2, the WR signal is asserted. Depending upon the instruction, either the
MREQ or IORQ signal is asserted. If the external WAIT pin is driven Low at least one CPU
system clock cycle prior to the end of State T2, additional wait states (TWAIT) are asserted
until the WAIT pin is driven High.
STATE T3
During State T3, no bus signals are altered.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
72
Z80® bus mode Read and Write timing is displayed in Figure 10 and Figure 11 on page
73. The Z80 bus mode states are configured for 1 to 15 CPU system clock cycles. In the
figures, each Z80 bus mode state is two CPU system clock cycles in duration. The figures
also display the assertion of 1 wait state (TWAIT) by the external peripheral during each
Z80 bus mode cycle.
T1
T2
TCLK
T3
System Clock
ADDR[23:0]
DATA[7:0]
CSx
RD
WAIT
WR
MREQ
or IORQ
Figure 10. Example: Z80 Bus Mode Read Timing
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
73
T1
T2
TCLK
T3
System Clock
ADDR[23:0]
DATA[7:0]
CSx
RD
WAIT
WR
MREQ
or IORQ
Figure 11. Example: Z80® Bus Mode Write Timing
Intel Bus Mode
Chip selects configured for Intel bus mode modify the CPU bus signals to duplicate a 
four-state memory transfer similar to that found on Intel-style microcontrollers. The bus
signals and eZ80F91 pins are mapped as displayed in Figure 12 on page 74. In Intel bus
mode, you select either multiplexed or nonmultiplexed address and data buses. In
nonmultiplexed operation, the address and data buses are separate. In multiplexed
operation, the lower byte of the address, ADDR[7:0], also appears on the data bus,
DATA[7:0], during State T1 of the Intel bus mode cycle.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
74
Bus Mode
Controller
eZ80 Bus Mode
Signals (Pins)
Intel Bus
Signal Equvalents
INSTRD
ALE
RD
RD
WR
WR
WAIT
READY
MREQ
MREQ
IORQ
IORQ
ADDR[23:0]
ADDR[23:0]
ADDR[7:0]
DATA[7:0]
Multiplexed
Bus
Controller
DATA[7:0]
Figure 12. Intel Bus Mode Signal and Pin Mapping
Intel™ Bus Mode—Separate Address and Data Buses
During Read operations with separate address and data buses, the Intel bus mode employs
four states—T1, T2, T3, and T4 as listed in Table 21.
Table 21. Intel Bus Mode Read States—Separate Address and Data Buses
STATE T1
The Read cycle begins in State T1. The CPU drives the address onto the address bus and
the associated chip select signal is asserted. The CPU drives the ALE signal High at the
beginning of T1. In the middle of T1, the CPU drives ALE Low to facilitate the latching of the
address.
STATE T2
During State T2, the CPU asserts the RD signal. Depending on the instruction, either the
MREQ or IORQ signal is asserted.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
75
Table 21. Intel Bus Mode Read States—Separate Address and Data Buses (Continued)
STATE T3
During State T3, no bus signals are altered. If the external READY (WAIT) pin is driven Low
at least one CPU system clock cycle prior to the beginning of State T3, additional wait states
(TWAIT) are asserted until the READY pin is driven High.
STATE T4
The CPU latches the Read data at the beginning of State T4. The CPU deasserts the RD
signal and completes the Intel bus mode cycle.
During Write operations with separate address and data buses, the Intel bus mode employs
four states—T1, T2, T3, and T4 as listed in Table 22.
Table 22. Intel Bus Mode Write States—Separate Address and Data Buses
STATE T1
The Write cycle begins in State T1. The CPU drives the address onto the address bus, the
associated chip select signal is asserted, and the data is driven onto the data bus. The CPU
drives the ALE signal High at the beginning of T1. During the middle of T1, the CPU drives
ALE Low to facilitate the latching of the address.
STATE T2
During State T2, the CPU asserts the WR signal. Depending on the instruction, either the
MREQ or IORQ signal is asserted.
STATE T3
During State T3, no bus signals are altered. If the external READY (WAIT) pin is driven Low
at least one CPU system clock cycle prior to the beginning of State T3, additional wait states
(TWAIT) are asserted until the READY pin is driven High.
STATE T4
The CPU deasserts the WR signal at the beginning of State T4. The CPU holds the data
and address buses till the end of T4. The bus cycle is completed at the end of T4.
Intel bus mode timing is displayed for a Read operation in Figure 13 on page 76 and for a
Write operation in Figure 14 on page 77. If the READY signal (external WAIT pin) is
driven Low prior to the beginning of State T3, additional wait states (TWAIT) are asserted
until the READY signal is driven High. The Intel bus mode states are configured for 2 to
15 CPU system clock cycles. In the Figure 13 on page 76 and Figure 14 on page 77, each
Intel bus mode state is 2 CPU system clock cycles in duration. Figure 13 on page 76 and
Figure 14 on page 77 also display the assertion of one Wait state (TWAIT) by the selected
peripheral.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
76
T1
T2
T3
TWAIT
T4
System Clock
ADDR[23:0]
DATA[7:0]
CSx
ALE
RD
READY
WR
MREQ
or IORQ
Figure 13. Example: Intel Bus Mode Read Timing—Separate Address and Data Buses
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
77
T1
T2
T3
TWAIT
T4
System Clock
ADDR[23:0]
DATA[7:0]
CSx
ALE
WR
READY
RD
MREQ
or IORQ
Figure 14. Example: Intel Bus Mode Write Timing—Separate Address and Data Buses
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
78
Intel™ Bus Mode—Multiplexed Address and Data Bus
During Read operations with multiplexed address and data, the Intel™ bus mode employs
four states—T1, T2, T3, and T4 as listed in Table 23.
Table 23. Intel Bus Mode Read States—Multiplexed Address and Data Bus
STATE T1
The Read cycle begins in State T1. The CPU drives the address onto the DATA bus and the
associated chip select signal is asserted. The CPU drives the ALE signal High at the
beginning of T1. In the middle of T1, the CPU drives ALE Low to facilitate the latching of the
address.
STATE T2
During State T2, the CPU removes the address from the DATA bus and asserts the RD
signal. Depending upon the instruction, either the MREQ or IORQ signal is asserted.
STATE T3
During State T3, no bus signals are altered. If the external READY (WAIT) pin is driven Low
at least one CPU system clock cycle prior to the beginning of State T3, additional wait states
(TWAIT) are asserted until the READY pin is driven High.
STATE T4
The CPU latches the Read data at the beginning of State T4. The CPU deasserts the RD
signal and completes the Intel™ bus mode cycle.
During Write operations with multiplexed address and data, the Intel™ bus mode employs
four states—T1, T2, T3, and T4 as listed in Table 24.
Table 24. Intel Bus Mode Write States—Multiplexed Address and Data Bus
STATE T1
The Write cycle begins in State T1. The CPU drives the address onto the DATA bus and
drives the ALE signal High at the beginning of T1. During the middle of T1, the CPU drives
ALE Low to facilitate the latching of the address.
STATE T2
During State T2, the CPU removes the address from the DATA bus and drives the Write
data onto the DATA bus. The WR signal is asserted to indicate a Write operation.
STATE T3
During State T3, no bus signals are altered. If the external READY (WAIT) pin is driven Low
at least one CPU system clock cycle prior to the beginning of State T3, additional wait states
(TWAIT) are asserted until the READY pin is driven High.
STATE T4
The CPU deasserts the Write signal at the beginning of T4 identifying the end of the Write
operation. The CPU holds the data and address buses through the end of T4. The bus cycle
is completed at the end of T4.
Signal timing for Intel bus mode with multiplexed address and data is displayed for a Read
operation in Figure 15 on page 79 and for a Write operation in Figure 16 on page 80. In
Figure 15 on page 79 and Figure 16 on page 80, each Intel bus mode state is 2 CPU system
clock cycles in duration. Figure 15 on page 79 and Figure 16 on page 80 also display the
assertion of one wait state (TWAIT) by the selected peripheral.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
79
T1
T2
T3
TWAIT
T4
System Clock
ADDR[23:0]
DATA[7:0]
CSx
ALE
RD
READY
WR
MREQ
or IORQ
Figure 15. Example: Intel Bus Mode Read Timing—Multiplexed Address and Data Bus
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
80
T1
T2
T3
TWAIT
T4
System Clock
ADDR[23:0]
DATA[7:0]
CSx
ALE
WR
READY
RD
MREQ
or IORQ
Figure 16. Example: Intel Bus Mode Write Timing—Multiplexed Address and Data Bus
Motorola Bus Mode
Chip selects configured for Motorola bus mode modify the CPU bus signals to duplicate
an eight-state memory transfer similar to that on the Motorola-style microcontrollers. The
bus signals (and eZ80F91 I/O pins) are mapped as displayed in Figure 17 on page 81.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
81
Bus Mode
Controller
eZ80 Bus Mode
Signals (Pins)
Motorola Bus
Signal Equvalents
INSTRD
AS
RD
DS
WR
R/W
WAIT
DTACK
MREQ
MREQ
IORQ
IORQ
ADDR[23:0]
DATA[7:0]
ADDR[23:0]
DATA[7:0]
Figure 17. Motorola Bus Mode Signal and Pin Mapping
During Write operations, the Motorola bus mode employs eight states—S0, S1, S2, S3,
S4, S5, S6, and S7 as listed in Table 25.
Table 25. Motorola Bus Mode Read States
STATE S0
The Read cycle starts in state S0. The CPU drives R/W High to identify a Read cycle.
STATE S1
Entering state S1, the CPU drives a valid address on the address bus, ADDR[23:0].
STATE S2
On the rising edge of state S2, the CPU asserts AS and DS.
STATE S3
During state S3, no bus signals are altered.
STATE S4
During state S4, the CPU waits for a cycle termination signal DTACK (WAIT), a peripheral
signal. If the termination signal is not asserted at least one full CPU clock period prior to the
rising clock edge at the end of S4, the CPU inserts WAIT (TWAIT) states until DTACK is
asserted. Each wait state is a full bus mode cycle.
STATE S5
During state S5, no bus signals are altered.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
82
Table 25. Motorola Bus Mode Read States (Continued)
STATE S6
During state S6, data from the external peripheral device is driven onto the data bus.
STATE S7
On the rising edge of the clock entering state S7, the CPU latches data from the addressed
peripheral device and deasserts AS and DS. The peripheral device deasserts DTACK at
this time.
The eight states for a Write operation in Motorola bus mode are listed in Table 26.
Table 26. Motorola Bus Mode Write States
STATE S0
The Write cycle starts in S0. The CPU drives R/W High (if a preceding Write cycle leaves R/
W Low).
STATE S1
Entering S1, the CPU drives a valid address on the address bus.
STATE S2
On the rising edge of S2, the CPU asserts AS and drives R/W Low.
STATE S3
During S3, the data bus is driven out of the high-impedance state as the data to be written is
placed on the bus.
STATE S4
At the rising edge of S4, the CPU asserts DS. The CPU waits for a cycle termination signal
DTACK (WAIT). If the termination signal is not asserted at least one full CPU clock period
prior to the rising clock edge at the end of S4, the CPU inserts WAIT (TWAIT) states until
DTACK is asserted. Each wait state is a full bus mode cycle.
STATE S5
During S5, no bus signals are altered.
STATE S6
During S6, no bus signals are altered.
STATE S7
On entering S7, the CPU deasserts AS and DS. As the clock rises at the end of S7, the CPU
drives R/W High. The peripheral device deasserts DTACK at this time.
Signal timing for Motorola bus mode is displayed for a Read operation in Figure 18 on
page 83 and for a Write operation in Figure 19 on page 84. In these two figures, each
Motorola bus mode state is 2 CPU system clock cycles in duration.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
83
S0
S1
S2
S3
S4
S5
S6
S7
System Clock
ADDR[23:0]
DATA[7:0]
CSx
AS
DS
R/W
DTACK
MREQ
or IORQ
Figure 18. Example: Motorola Bus Mode Read Timing
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
84
S0
S1
S2
S3
S4
S5
S6
S7
System Clock
ADDR[23:0]
DATA[7:0]
CSx
AS
DS
R/W
DTACK
MREQ
or IORQ
Figure 19. Example: Motorola Bus Mode Write Timing
Switching Between Bus Modes
When switching bus modes between Intel™ to Motorola, Motorola to Intel™, eZ80® to
Motorola, or eZ80 to Intel™, there is one extra SCLK cycle added to the bus access. An
extra clock cycle is not required for repeated access in any of the bus modes (for example,
Intel™ to Intel™). An extra clock cycle is not required for Intel™ (or Motorola) to eZ80
bus mode (under normal operation). The extra clock cycle is not shown in the timing
examples. Due to the asynchronous nature of these bus protocols, the extra delay does not
impact peripheral communication.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
85
Chip Select Registers
Chip Select x Lower Bound Register
For Memory chip selects, the chip select x Lower Bound register (see Table 27) defines
the lower bound of the address range for which the corresponding Memory chip select (if
enabled) is active. For I/O chip selects, the chip select x Lower Bound register defines the
address to which ADDR[15:8] is compared to generate an I/O chip select. All chip select
lower bound registers reset to 00h.
Table 27. Chip Select x Lower Bound Register (CS0_LBR = 00A8h, CS1_LBR = 00ABh,
CS2_LBR = 00AEh, CS3_LBR = 00B1h)
Bit
7
6
5
4
3
2
1
0
CS0_LBR Reset
0
0
0
0
0
0
0
0
CS1_LBR Reset
0
0
0
0
0
0
0
0
CS2_LBR Reset
0
0
0
0
0
0
0
0
CS3_LBR Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value Description
[7:0]
CSX_LBR
00h–
FFh
For Memory Chip Selects (CSx_IO = 0)
This byte specifies the lower bound of the chip select address
range. The upper byte of the address bus, ADDR[23:16], is
compared to the values contained in these registers for
determining whether a Memory chip select signal must be
generated.
For I/O Chip Selects (CSx_IO = 1)
This byte specifies the chip select address value. ADDR[15:8] is
compared to the values contained in these registers for
determining whether an I/O chip select signal must be generated.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
86
Chip Select x Upper Bound Register
For Memory chip selects, the Chip Select x Upper Bound registers, listed in Table 28,
defines the upper bound of the address range for which the corresponding Chip Select (if
enabled) are active. For I/O chip selects, this register produces no effect. The reset state for
the Chip Select 0 Upper Bound register is FFh when the reset state for the other Chip
Select Upper Bound registers is 00h.
Table 28. Chip Select x Upper Bound Register (CS0_UBR = 00A9h, CS1_UBR = 00ACh,
CS2_UBR = 00AFh, CS3_UBR = 00B2h)
Bit
7
6
5
4
3
2
1
0
CS0_UBR Reset
1
1
1
1
1
1
1
1
CS1_UBR Reset
0
0
0
0
0
0
0
0
CS2_UBR Reset
0
0
0
0
0
0
0
0
CS3_UBR Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value Description
[7:0]
CSX_UBR
00h–
FFh
For Memory Chip Selects (CSx_IO = 0)
This byte specifies the upper bound of the chip select address
range. The upper byte of the address bus, ADDR[23:16], is
compared to the values contained in these registers for
determining whether a chip select signal must be generated.
For I/O Chip Selects (CSx_IO = 1)
No effect.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
87
Chip Select x Control Register
The Chip Select x Control register (see Table 29) enables the chip selects, specifies the
type of chip select, and sets the number of wait states. The reset state for the Chip Select 0
Control register is E8h when the reset state for three other Chip Select Control registers is
00h.
Table 29. Chip Select x Control Register (CS0_CTL = 00AAh, CS1_CTL = 00ADh,
CS2_CTL = 00B0h, CS3_CTL = 00B3h)
Bit
7
6
5
4
3
2
1
0
CS0_CTL Reset
1
1
1
0
1
0
0
0
CS1_CTL Reset
0
0
0
0
0
0
0
0
CS2_CTL Reset
0
0
0
0
0
0
0
0
CS3_CTL Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R
R
R
CPU Access
Note: R/W = Read/Write; R = Read Only.
Bit 
Position
[7:5]
CSX_WAIT
Value Description
000
0 wait states are asserted when this chip select is active.
001
1 wait state is asserted when this chip select is active.
010
2 wait states are asserted when this chip select is active.
011
3 wait states are asserted when this chip select is active.
100
4 wait states are asserted when this chip select is active.
101
5 wait states are asserted when this chip select is active.
110
6 wait states are asserted when this chip select is active.
111
7 wait states are asserted when this chip select is active.
0
Chip select is configured as a memory chip select.
1
Chip select is configured as an I/O chip select.
3
CSX_EN
0
Chip select is disabled.
1
Chip select is enabled.
[2:0]
000
Reserved.
4
CSX_IO
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
88
Chip Select x Bus Mode Control Register
The Chip Select Bus Mode register (see Table 30) configures the chip select for eZ80®,
Z80®, Intel™, or Motorola bus modes. Changing the bus mode allows the eZ80F91 device
to interface to peripherals based on the Z80, Intel™, or Motorola style asynchronous bus
interfaces. When a bus mode other than eZ80 is programmed for a particular chip select,
the CSx_WAIT setting in that Chip Select Control Register is ignored.
Table 30. Chip Select x Bus Mode Control Register (CS0_BMC = 00F0h, CS1_BMC =
00F1h, CS2_BMC = 00F2h, CS3_BMC = 00F3h)
Bit
7
6
5
4
3
2
1
0
CS0_BMC Reset
0
0
0
0
0
0
1
0
CS1_BMC Reset
0
0
0
0
0
0
1
0
CS2_BMC Reset
0
0
0
0
0
0
1
0
CS3_BMC Reset
0
0
0
0
0
0
1
0
R/W
R/W
R/W
R
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write; R = Read Only.
Bit 
Position
Value Description
00
eZ80 bus mode
01
Z80 bus mode
10
Intel™ bus mode
11
Motorola bus mode
5
AD_MUX
0
Separate address and data
1
Multiplexed address and data—appears on data bus
DATA[7:0]
4
0
Reserved
[7:6]
BUS_MODE
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
89
Bit 
Position
[3:0]
BUS_CYCLE
Value Description
0000
Not valid.
0001
Each bus mode state is 1 eZ80® clock cycle in duration.1, 2, 3
0010
Each bus mode state is 2 eZ80 clock cycles in duration.
0011
Each bus mode state is 3 eZ80 clock cycles in duration.
0100
Each bus mode state is 4 eZ80 clock cycles in duration.
0101
Each bus mode state is 5 eZ80 clock cycles in duration.
0110
Each bus mode state is 6 eZ80 clock cycles in duration.
0111
Each bus mode state is 7 eZ80 clock cycles in duration.
1000
Each bus mode state is 8 eZ80 clock cycles in duration.
1001
Each bus mode state is 9 eZ80 clock cycles in duration.
1010
Each bus mode state is 10 eZ80 clock cycles in duration.
1011
Each bus mode state is 11 eZ80 clock cycles in duration.
1100
Each bus mode state is 12 eZ80 clock cycles in duration.
1101
Each bus mode state is 13 eZ80 clock cycles in duration.
1110
Each bus mode state is 14 eZ80 clock cycles in duration.
1111
Each bus mode state is 15 eZ80 clock cycles in duration.
Notes
1. Setting the BUS_CYCLE to 1 in Intel bus mode causes the ALE pin to not function properly.
2. Use of the external WAIT input pin in Z80 mode requires that BUS_CYCLE is set to a value
greater than 1.
3. BUS_CYCLE produces no effect in eZ80 mode.
Bus Arbiter
The Bus Arbiter within the eZ80F91 allows external bus masters to gain control of the
CPU memory interface bus. During normal operation, the eZ80F91 device is the bus master. External devices request master use of the bus by asserting the BUSREQ pin. The Bus
Arbiter forces the CPU to release the bus after completing the current instruction. When
the CPU releases the bus, the Bus Arbiter asserts the BUSACK pin to notify the external
device that it can master the bus. When an external device assumes control of the memory
interface bus, the bus acknowledge cycle is complete. Table 31 on page 90 lists the status
of the pins on the eZ80F91 device during bus acknowledge cycles.
During a bus acknowledge cycle, the bus interface pins of the eZ80F91 device are used by
an external bus master to control the memory and I/O chip selects.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
90
Table 31. eZ80F91 Pin Status During Bus Acknowledge Cycles
Pin Symbol
Signal Direction
Description
ADDR23..ADDR0
Input
Allows external bus master to utilize the chip
select logic of the eZ80F91.
CS0
Output
Normal operation.
CS1
Output
Normal operation.
CS2
Output
Normal operation.
CS3
Output
Normal operation.
DATA7..0
Tristate
Allows external bus master to communicate
with external peripherals.
IORQ
Input
Allows external bus master to utilize the chip
select logic of the eZ80F91.
MREQ
Input
Allows external bus master to utilize the chip
select logic of the eZ80F91.
RD
Tristate
Allows external bus master to communicate
with external peripherals.
WR
Tristate
Allows external bus master to communicate
with external peripherals.
INSTRD
Tristate
Allows external bus master to communicate
with external peripherals.
Normal bus operation of the eZ80F91 device using CS0 to communicate to an external
peripheral is displayed in Figure 20 on page 91. Figure 21 on page 91 displays an external
bus master communicating with an external peripheral during bus acknowledge cycles.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
91
WAIT
RD
WR
External
Master
External
Peripheral
DATA
ADDRESS
IORQ
MREQ
eZ80F91
Chip Select
Wait State
Generator
CS0
CS1
CS2
CS3
Figure 20. Memory Interface Bus Operation During CPU Bus Cycles, Normal Operation
WAIT
RD
WR
External
Master
External
Peripheral
DATA
ADDRESS
IORQ
MREQ
eZ80F91
Chip Select
Wait State
Generator
CS0
CS1
CS2
CS3
Figure 21. Memory Interface Bus Operation During Bus Acknowledge Cycles
During bus acknowledge cycles, the Memory and I/O chip select logic is controlled by the
external address bus and external IORQ and MREQ signals.
PS019215-0910
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
92
The following chip select features are not available during bus acknowledge cycles:
PS019215-0910
•
The chip select logic does not insert wait states during bus acknowledge cycles regardless of the WAIT configuration for the decoded chip select.
•
•
The bus mode controller does not function during bus acknowledge cycles.
Internal registers and memory addresses in the eZ80F91 device are not accessible during bus acknowledge cycles.
Chip Selects and Wait States
eZ80F91 MCU
Product Specification
93
Random Access Memory
The eZ80F91 device features 8 KB (8192 bytes) of single-port data Random Access
Memory (RAM) for general-purpose use and 8 KB of RAM for the EMAC. RAM is
enabled or disabled, and it is relocated to the top of any 64 KB page in memory. Data is
passed to and from RAM via the 8-bit data bus. On-chip RAM operates with zero wait
states. EMAC RAM is accessed via the bus arbiter and executes with zero or one Wait
states.
General-purpose RAM occupies memory addresses in the RAM Address Upper Byte register in the range {RAM_ADDR_U[7:0], E000h} to {RAM_ADDR_U[7:0], FFFFh}.
EMAC RAM occupies memory addresses in the range {RAM_ADDR_U[7:0], C000h}
to {RAM_ADDR_U[7:0], DFFFh}. Following a RESET, RAM is enabled when
RAM_ADDR_U is set to FFh. Figure 22 displays a memory map for on-chip RAM. In
this example, RAM_ADDR_U is set to 7Ah. Figure 22 is not drawn to scale, as RAM
occupies only a very small fraction of the available 16 MB address space.
Memory
Location
FFFFFFh
7AFFFFh
7AE000h
7ADFFFh
8 KB
General-Purpose
RAM
8 KB
EMAC SRAM
RAM_ADDR_U
7Ah
7AC000h
000000h
Figure 22. Example: eZ80F91 On-Chip RAM Memory Addressing
When enabled, on-chip RAM assumes priority over on-chip Flash memory and any memory chip selects that is also enabled in the same address space. If an address is generated in
a range that is covered by both the RAM address space and a particular memory chip
PS019215-0910
Random Access Memory
eZ80F91 MCU
Product Specification
94
select address space, the memory chip select is not activated. On-chip RAM is not accessible to external devices during bus acknowledge cycles.
RAM Control Registers
RAM Control Register
Internal general-purpose RAM is disabled by clearing the GPRAM_EN bit. The default on
RESET is for general-purpose RAM to be enabled. See Table 32.
Table 32. RAM Control Register (RAM_CTL = 00B4h)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
0
0
0
0
0
0
R/W
R/W
R
R
R
R
R
R
CPU Access
Note: R/W = Read/Write; R = Read Only.
Bit 
Position
PS019215-0910
Value
Description
7
GPRAM_EN
0
On-chip general-purpose RAM is disabled.
1
On-chip general-purpose RAM is enabled.
6
ERAM_EN
0
On-chip EMAC RAM is disabled.
1
On-chip EMAC RAM is enabled.
[5:0]
000000
Reserved.
Random Access Memory
eZ80F91 MCU
Product Specification
95
RAM Address Upper Byte Register
The RAM_ADDR_U register defines the upper byte of the address for on-chip RAM. 
If enabled, RAM addresses assume priority over all Chip Selects. The external Chip Select
signals are not asserted if the corresponding RAM address is enabled. See Table 33.
Table 33. RAM Address Upper Byte Register (RAM_ADDR_U = 00B5h)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
1
1
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value Description
[7:0]
00h–
RAM_ADDR_U FFh
PS019215-0910
This byte defines the upper byte of the RAM address. When
enabled, the general-purpose RAM address space ranges from
{RAM_ADDR_U, E000h} to {RAM_ADDR_U, FFFFh}. When
enabled, the EMAC RAM address space ranges from
{RAM_ADDR_U, C000h} to {RAM_ADDR_U, DFFFh}.
Random Access Memory
eZ80F91 MCU
Product Specification
96
MBIST Control
There are two Memory Built-In Self-Test (MBIST) controllers for the RAM blocks on the
eZ80F91. MBIST_GPR is for General-Purpose RAM and MBIST_EMR is for EMAC
RAM. Writing a 1 to MBIST_ON starts the MBIST testing. Writing a 0 to MBIST_ON
stops the MBIST testing. On completion of the MBIST testing, MBIST_ON is
automatically reset to 0. If RAM passes MBIST testing, MBIST_PASS is 1. The value in
MBIST_PASS is only valid when MBIST_DONE is High. See Table 34.
Table 34. MBIST Control Register (MBIST_GPR = 00B6h, MBIST_EMR = 00B7h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R
R
R
R
R
R
R
CPU Access
Note: R/W = Read/Write; R = Read Only.
PS019215-0910
Bit Position
Value
Description
7
MBIST_ON
0
MBIST Testing of the RAM is disabled.
1
MBIST Testing of the RAM is enabled.
6
MBIST_DONE
0
MBIST Testing has not completed.
1
MBIST Testing has completed.
5
MBIST_PASS
0
MBIST Testing has failed.
1
MBIST Testing has passed.
[4:0]
00000
Reserved.
Random Access Memory
eZ80F91 MCU
Product Specification
97
Flash Memory
The eZ80F91 device features 256 KB (262,144 bytes) of non-volatile Flash memory with
Read/Write/Erase capability. The main Flash memory array is arranged in 128 pages with
8 rows per page and 256 bytes per row. In addition to main Flash memory, there are two
separately addressable rows which comprise a 512-byte information page.
In eight 32 KB blocks, 256 KB of main storage is protected. Protecting a 32 KB block
prevents Write or Erase operations. The lower 32 KB block (00000h–07FFFh) is protected using the external WP pin. This portion of memory is called the Boot block because
the CPU always starts executing code from this location at startup. If the application
requires external program memory, then the Boot block must at least contain a jump
instruction to move the Program Counter outside of the Flash memory space.
The Flash memory arrangement is displayed in Figure 23.
8
32 KB blocks
7
6
5
4
3
2
1
0
16
2 KB pages
per block
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
0
8
256-byte rows
per page
7
6
5
4
3
2
1
0
256
single-byte columns
per row
255 254
1
0
Figure 23. eZ80F91 Flash Memory Arrangement
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
98
Flash Memory Overview
The eZ80F91 device includes a Flash memory controller that automatically converts 
standard CPU Read and Write cycles to the specific protocol required for the Flash
memory array. As such, standard memory Read and Write instructions access the Flash
memory array as if it is internal RAM. The controller also supports I/O access to the Flash
memory array, in effect presenting it as an indirectly addressable bank of I/O registers.
These access methods are also supported via the ZDI and OCI™ interfaces.
In addition, eZ80Acclaim!® Flash Microcontrollers support a Flash Read–While–Write
methodology. In other words, the eZ80® CPU continues to read and execute code from an
area of Flash memory when a nonconflicting area of Flash memory is being programmed.
The Flash memory controller contains a frequency divider, a Flash register interface, and a
Flash control state machine. A simplified block diagram of the Flash controller is
displayed in Figure 24.
System Clock
eZ80 Core
Interface
Clock Divider
8-bit downcounter
ADDR 17
DOUT 8
FADDR
17
FDIN
8
FCNTL
9
Flash
MAIN_INFO
State
Machine
FDOUT 8
Flash
256 KB
+
512 bytes
Flash
Control
Registers
CPUD OUT
8
FLASH_IRQ
Figure 24. Flash Memory Block Diagram
Reading Flash Memory
The main Flash memory array is read using both memory and I/O operations. As an auxiliary storage area, the information page is only accessible via I/O operations. In all cases,
Wait states are automatically inserted to allow for read access time.
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
99
Memory Read
A memory Read operation uses the address bus and data bus of the eZ80F91 device to
read a single data byte from Flash memory. This Read operation is similar to reads from
RAM. To perform Flash memory reads, the FLASH_CTRL register must be configured to
enable memory access to Flash with the appropriate number of wait states. See Table 38
on page 105.
Only the main area of Flash memory is accessible via memory reads. The information
page must be read using I/O access.
I/O Read
A single-byte I/O Read operation uses I/O registers for setting the column, page, and row
address to be read. A Read of the FLASH_DATA register returns the contents of Flash
memory at the designated address. Each access to the FLASH_DATA register causes an
autoincrement of the Flash address stored in the Flash address registers (FLASH_PAGE,
FLASH_ROW, FLASH_COL). To allow for Flash memory access time, the
FLASH_CTRL register must be configured with the appropriate number of wait states.
See Table 38 on page 105.
Programming Flash Memory
Flash memory is programmed using standard I/O or memory Write operations that the
Flash memory controller automatically translates to the detailed timing and protocol
required for Flash memory. The more efficient multibyte (row) programming mode is only
available via I/O Writes.
Note: To ensure data integrity and device reliability, two main restrictions exist on programming
of Flash memory:
1. The cumulative programming time since the last erase cannot exceed 31 ms for any
given row.
2. The same byte cannot be programmed more than once since the last erase.
Single-Byte I/O Write
A single-byte I/O Write operation uses I/O registers for setting the column, page, and row
address to be written. The FLASH_DATA register stores the data to be written. While the
CPU executes an I/O instruction to load the data into the FLASH_DATA register, the
Flash controller asserts the internal WAIT signal to stall the CPU until the Flash Write
operation is complete. A single-byte Write takes between 66 µs and 85 µs to complete.
Programming an entire row (256 bytes) using single-byte Writes therefore takes no more
than 21.8 ms. This duration of time does not include the time required by the CPU to
transfer data to the registers which is a function of the instructions employed and the 
system clock frequency. Each access to the FLASH_DATA register causes an
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
100
autoincrement of the Flash address stored in the Flash Address registers (FLASH_PAGE,
FLASH_ROW, FLASH_COL).
A typical sequence that performs a single-byte I/O Write is shown below. Because the
Write is self-timed, step 2 of the sequence is repeated back-to-back without requiring polling or interrupts.
1. Write the FLASH_PAGE, FLASH_ROW, and FLASH_COL registers with the
address of the byte to be written.
2. Write the data value to the FLASH_DATA register.
Multibyte I/O Write (Row Programming)
Multibyte I/O Write operations use the same I/O registers as single-byte Writes. 
Multibyte I/O Writes allow the programming of full row and are enabled by setting the
ROW_PGM bit of the Flash Program Control Register. For multibyte I/O Writes, the CPU
sets the address registers, enables row programming, and then executes an I/O instruction
(with repeat) to load the block of data into the FLASH_DATA register. For each individual
byte written to the FLASH_DATA register during the block move, the Flash controller
asserts the internal WAIT signal to stall the CPU until the current byte is programmed.
Each access to the FLASH_DATA register causes an autoincrement of the Flash address
stored in the Flash Address registers (FLASH_PAGE, FLASH_ROW, FLASH_COL).
During row programming, the Flash controller continuously asserts the Flash memory’s
high voltage signal until all bytes are programmed (column address < 255). As a result, the
row programs more quickly than if the high-voltage signal is toggled for each byte. The
per-byte programming time during row programming is between 41 µs and 52µs. As such,
programming 256 bytes of a row in this mode takes not more than 13.4 ms, leaving 17.6
ms for CPU instruction overhead to fetch the 256 bytes.
A typical sequence that performs a multibyte I/O Write is shown below:
1. Check the FLASH_IRQ register to ensure that any previous row program is 
completed.
2. Write the FLASH_PAGE, FLASH_ROW, and FLASH_COL registers with the
address of the first byte to be written.
3. Set the ROW_PGM bit in the FLASH_PGCTL register to enable row programming
mode.
4. Write the next data value to the FLASH_DATA register.
5. If the end of the row has not been reached, return to step 4.
During row programming, software must monitor the row time-out error bit either by
enabling this interrupt or via polling. If a row time-out occurs, the Flash controller aborts
the row programming operation, and software must assure that no further Writes are 
performed to the row without it first being erased. It is suggested that row programming is
be used one time per row and not in combination with single-byte Writes to the same row
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
101
without first erasing it. Otherwise, the burden is on software to ensure that the 31 ms
maximum cumulative programming time between erases is not exceeded for a row.
Memory Write
A single-byte memory Write operation uses the address bus and data bus of the eZ80F91
device for programming a single data byte to Flash memory. While the CPU executes a
Load instruction, the Flash controller asserts the internal WAIT signal to stall the CPU
until the Write is complete. A single-byte Write takes between 66 µs and 85 µs to
complete. Programming an entire row using memory Writes therefore takes no more than
21.8 ms. This duration of time does not include time required by the CPU to transfer data
to the registers, which is a function of the instructions employed and the system clock
frequency.
The memory Write function does not support multibyte row programming. Because memory Writes are self-timed, they are performed back-to-back without requiring polling or
interrupts.
Erasing Flash Memory
Erasing bytes in Flash memory returns them to a value of FFh. Both the MASS and PAGE
ERASE operations are self-timed by the Flash controller, leaving the CPU free to execute
other operations in parallel. The DONE status bit in the Flash Interrupt Control Register
are polled by software or used as an interrupt source to signal completion of an Erase operation. If the CPU attempts to access Flash memory while an erase is in progress, the Flash
controller forces a wait state until the Erase operation is completed.
Mass Erase
Performing a MASS ERASE operation on Flash memory erases all bits contained in the
main Flash memory array. The information page remains unaffected unless the
FLASH_PAGE register bit 7(INFO_EN) is set. This self-timed operation takes
approximately 200 ms to complete.
Page Erase
The smallest erasable unit in Flash memory is a page. The pages to be erased, whether they
are the 128 main Flash memory pages or the information page, are determined by the setting of the FLASH_PAGE register. This self-timed operation takes approximately 10 ms to
complete.
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
102
Information Page Characteristics
As noted earlier, the information page is not accessible using memory access instructions
and must be accessed via the FLASH_DATA I/O register. The Flash Page Select Register
contains a bit which selects the information page for I/O access.
There are two ways to erase the information page. You must set the FLASH_PAGE register(0x00FC) bit7(INFO_EN) and then you execute either a MASS ERASE (which also
erases the entire main Flash memory array) operation or a PAGE ERASE operation.
Flash Control Registers
The Flash Control Register interface contains all the registers used in Flash memory. The
definitions in this section describe each register.
Flash Key Register
Writing the two-byte sequence B6h, 49h in immediate succession to this register unlocks
the Flash Divider and Flash Write/Erase Protection registers. If these values are not 
written by consecutive CPU I/O Writes (I/O reads and memory Read/Writes have no
effect), the Flash Divider and Flash Write/Erase Protection registers remain locked. This
prevents accidental overwrites of these critical Flash control register settings. Writing a
value to either the Flash Frequency Divider Register or the Flash Write/Erase Protection
Register automatically relocks both of the registers. See Table 35.
Table 35. Flash Key Register (FLASH_KEY = 00F5h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
PS019215-0910
Bit 
Position
Value Description
[7:0]
FLASH_KEY
B6h,
49h
Sequential Write operations of the values B6h, 49h to this
register will unlock the Flash Frequency Divider and Flash
Write/Erase Protection registers.
Flash Memory
eZ80F91 MCU
Product Specification
103
Flash Data Register
The Flash Data register stores the data values to be programmed into Flash memory via 
I/O Write operations. An I/O read of the Flash Data register returns data from Flash
memory. The Flash memory address used for I/O access is determined by the contents of
the page, row, and column registers. Each access to the FLASH_DATA register causes an
autoincrement of the Flash address stored in the Flash Address registers (FLASH_PAGE,
FLASH_ROW, FLASH_COL). See Table 36.
Table 36. Flash Data Register (FLASH_DATA = 00F6h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
PS019215-0910
Bit Position
Value
Description
[7:0]
FLASH_DATA
00h-FFh Data value to be written to Flash memory during an I/O Write
operation, or the data value that is read in Flash memory,
indicated by the Flash Address registers (FLASH_PAGE,
FLASH_ROW, FLASH_COL).
Flash Memory
eZ80F91 MCU
Product Specification
104
Flash Address Upper Byte Register
The FLASH_ADDR_U register defines the upper 6 bits of the Flash memory address
space. Changing the value of FLASH_ADDR_U allows on-chip 256 KB Flash memory
to be mapped to any location within the 16 MB linear address space of the eZ80F91
device. If on-chip Flash memory is enabled, the Flash address assumes priority over any
external Chip Selects. The external Chip Select signals are not asserted if the corresponding Flash address is enabled. Internal Flash memory does not hold priority over
internal SRAM. See Table 37.
Table 37. Flash Address Upper Byte Register (FLASH_ADDR_U = 00F7h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R
R
CPU Access
Note: R/W = Read/Write; R = Read Only.
Bit Position
Value
Description
[7:2]
00h–FCh These bits define the upper byte of the Flash address.
FLASH_ADDR_U
When on-chip Flash is enabled, the Flash address space
begins at address {FLASH_ADDR_U, 00b, 0000h}. On-chip
Flash has priority over all external Chip Selects.
[1:0]
PS019215-0910
00
Reserved (enforces alignment on a 256 KB boundary).
Flash Memory
eZ80F91 MCU
Product Specification
105
Flash Control Register
The Flash Control register enables or disables memory access to Flash memory. I/O access
to the Flash control registers and to Flash memory is still possible while Flash memory
space access is disabled.
The minimum access time of internal Flash memory is 60 ns. The Flash Control Register must be configured to provide the appropriate number of wait states based on the system clock frequency of the eZ80F91 device. Because the maximum SCLK frequency is
50 MHz (20 ns), the default on RESET is for four Wait states to be inserted for Flash
memory access (Flash memory access + one eZ80® Bus Cycle = 60 ns + 20 ns = 80 ns;
80 ns ÷ 20 ns = 4 Wait states). See Table 38.
Table 38. Flash Control Register (FLASH_CTRL = 00F8h)
Bit
7
6
5
4
3
2
1
0
Reset
1
0
0
0
1
0
0
0
R/W
R/W
R/W
R
R/W
R
R
R
CPU Access
Note: R/W = Read/Write, R = Read Only.
PS019215-0910
Bit Position
Value Description
[7:5]
FLASH_WAIT
000
0 wait states are inserted when the Flash is active.
001
1 wait state is inserted when the Flash is active.
010
2 wait states are inserted when the Flash is active.
011
3 wait states are inserted when the Flash is active.
100
4 wait states are inserted when the Flash is active.
101
5 wait states are inserted when the Flash is active.
110
6 wait states are inserted when the Flash is active.
111
7 wait states are inserted when the Flash is active.
[4]
0
Reserved.
[3]
FLASH_EN
0
Flash memory access is disabled.
1
Flash memory access is enabled.
[2:0]
000
Reserved.
Flash Memory
eZ80F91 MCU
Product Specification
106
Flash Frequency Divider Register
The 8-bit frequency divider allows the programming of Flash memory over a range of 
system clock frequencies. Flash is programmed with system clock frequencies ranging
from 154 kHz to 50 MHz. The Flash controller requires an input clock with a period that
falls within the range of 5.16.5 µs. The period of the Flash controller clock is set in the
Flash Frequency Divider Register. Writes to this register is allowed only after it is
unlocked via the FLASH_KEY register. The Flash Frequency Divider Register value
required versus the system clock frequency is listed in Table 39. System clock frequencies
outside of the ranges shown are not supported. Register values for the Flash Frequency
Divider are listed in Table 40.
Table 39. Flash Frequency Divider Values
System Clock Frequency
Flash Frequency Divider Value
154–196 kHz
1
308–392 kHz
2
462–588 kHz
3
616 kHz–50 MHz
CEILING [System Clock Frequency (MHz) x 5.1 (µs)]*
Note: *The CEILING function rounds fractional values up to the next whole number. For example,
CEILING(3.01) is 4.
Table 40. Flash Frequency Divider Register (FLASH_FDIV = 00F9h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
1
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W
CPU Access
Note: R/W = Read/Write, R = Read Only. *Key sequence required to enable Writes
PS019215-0910
Bit Position
Value
Description
[7:0]
FLASH_FDIV
01h–FFh Divider value for generating the required 5.1-6.5 µs Flash
controller clock period.
Flash Memory
eZ80F91 MCU
Product Specification
107
Flash Write/Erase Protection Register
The Flash Write/Erase Protection register prevents accidental Write or Erase operations.
The protection is limited to a resolution of eight 32 KB blocks. Setting a bit to 1 protects
that 32 KB block of Flash memory from accidental Writes or Erases. The default upon
RESET is for all Flash memory blocks to be protected.
The WP pin works in conjunction with FLASH_PROT[0] to protect the lowest block (also
called the Boot block) of Flash memory. If either the WP is held asserted or
FLASH_PROT[0] is set, the Boot block is protected from Write and Erase operations.
Note:
A protect bit is not available for the information page. The information page is, however,
protected excluded from a MASS ERASE by clearing the FLASH_PAGE register
(0x00FC) bit7(INFO_EN).
Writes to this register is allowed only after it is unlocked via the FLASH_KEY register.
Any attempted Writes to this register while locked will set it to FFh, thereby protecting all
blocks. See Table 41.
Table 41. Flash Write/Erase Protection Register (FLASH_PROT = 00FAh)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
1
1
1
1
1
1
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: R/W = Read/Write if unlocked, R = Read Only if locked. *Key sequence required to unlock.
PS019215-0910
Bit Position
Value Description
[7]
BLK7_PROT
0
Disable Write/Erase Protect on block 38000h to 3FFFFh.
1
Enable Write/Erase Protect on block 38000h to 3FFFFh.
[6]
BLK6_PROT
0
Disable Write/Erase Protect on block 30000h to 37FFFh.
1
Enable Write/Erase Protect on block 30000h to 37FFFh.
[5]
BLK5_PROT
0
Disable Write/Erase Protect on block 28000h to 2FFFFh.
1
Enable Write/Erase Protect on block 28000h to 2FFFFh.
[4]
BLK4_PROT
0
Disable Write/Erase Protect on block 20000h to 27FFFh.
1
Enable Write/Erase Protect on block 20000h to 27FFFh.
[3]
BLK3_PROT
0
Disable Write/Erase Protect on block 18000h to 1FFFFh.
1
Enable Write/Erase Protect on block 18000h to 1FFFFh.
[2]
BLK2_PROT
0
Disable Write/Erase Protect on block 10000h to 17FFFh.
1
Enable Write/Erase Protect on block 10000h to 17FFFh.
Flash Memory
eZ80F91 MCU
Product Specification
108
Bit Position
Value Description
[1]
BLK1_PROT
0
Disable Write/Erase Protect on block 08000h to 0FFFFh.
1
Enable Write/Erase Protect on block 08000h to 0FFFFh.
[0]
BLK0_PROT
0
Disable Write/Erase Protect on block 00000h to 07FFFh.
1
Enable Write/Erase Protect on block 00000h to 07FFFh.
Note: The lower 32 KB block (00000h to 07FFFh—BLK0) is called the Boot block and is protected
using the external WP pin.
Flash Interrupt Control Register
There are two sources of interrupts from the Flash controller. These two sources are:
•
•
Page Erase, Mass Erase, or Row Program completed successfully.
An error condition occurred.
Either or both of these two interrupt sources are enabled by setting the appropriate bits in
the Flash Interrupt Control register.
The Flash Interrupt Control register contains four status bits to indicate the following error
conditions:
Row Program Time-Out—This bit signals a time-out during Row Programming. If the
current row program operation does not complete within 4864 Flash controller clocks, 
the Flash controller terminates the row program operation by clearing bit 2 of the Flash
Program Control Register and sets the RP_TM0 error bit to 1.
Write Violation—This bit indicates an attempt to write to a protected block of Flash 
memory (the Write was not performed).
Page Erase Violation—This bit indicates an attempt to erase a protected block of Flash
memory (the requested page was not erased).
Mass Erase Violation—This bit indicates an attempt to MASS ERASE when there are
one or more protected blocks in Flash memory (the MASS ERASE was not performed).
If the error condition interrupt is enabled, any of these four error conditions result in an
interrupt request being sent to the eZ80F91device’s interrupt controller. Reading the Flash
Interrupt Control register clears all error condition flags and the DONE flag. See Table 42
on page 109.
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
109
Table 42. Flash Interrupt Control Register (FLASH_IRQ = 00FBh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R
R
R
R
R
R
CPU Access
Note: R/W = Read/Write, R = Read Only. Read resets bits [5] and [3:0].
Bit Position
Value Description
[7]
DONE_IEN
0
Flash Erase/Row Program Done Interrupt is disabled.
1
Flash Erase/Row Program Done Interrupt is enabled.
[6]
ERR_IEN
0
Error Condition Interrupt is disabled.
1
Error Condition Interrupt is enabled.
[5]
DONE
0
Erase/Row Program Done Flag is not set.
1
Erase/Row Program Done Flag is set.
[4]
0
Reserved.
[3]
WR_VIO
0
The Write Violation Error Flag is not set.
1
The Write Violation Error Flag is set.
[2]
RP_TMO
0
The Row Program Time-Out Error Flag is not set.
1
The Row Program Time-Out Error Flag is set.
[1]
PG_VIO
0
The Page Erase Violation Error Flag is not set.
1
The Page Erase Violation Error Flag is set.
[0]
MASS_VIO
0
The Mass Erase Violation Error Flag is not set.
1
The Mass Erase Violation Error Flag is set.
Note: The lower 32 KB block (00000h to 07FFFh) is called the Boot Block and is protected using
the external WP pin. Attempts to page erase BLK0 or mass erase Flash when WP is asserted
result in failure and signal an erase violation.
Flash Page Select Register
The msb of this register is used to select whether I/O Flash access and PAGE ERASE
operations are directed to the 512-byte information page or to the main Flash memory
array, and also whether the information page is included in MASS ERASE operations. The
lower 7 bits are used to select one of the main 128 pages for PAGE ERASE or I/O 
operations.
To perform a PAGE ERASE, the software must set the proper page value prior to setting
the page erase bit in the Flash Control Register. In addition, each access to the
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
110
FLASH_DATA register causes an autoincrement of the Flash address stored in the Flash
Address registers (FLASH_PAGE, FLASH_ROW, FLASH_COL). See Table 43.
Table 43. Flash Page Select Register (FLASH_PAGE = 00FCh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write, R = Read Only.
Bit 
Position
[7]
INFO_EN
[6:0]
FLASH_PAGE
PS019215-0910
Value
Description
0
Flash I/O access to PAGE ERASE operations are directed to
main Flash memory. Info page is NOT affected by a MASS
ERASE operation.
1
Flash I/O access to PAGE ERASE operations are directed to
the information page. PAGE ERASE operations only affect
the information page. Info page is included during a MASS
ERASE operation.
00h–7Fh Page address of Flash memory to be used during the PAGE
ERASE or I/O access of main Flash memory. When
INFO_EN is set to 1, this field is ignored.
Flash Memory
eZ80F91 MCU
Product Specification
111
Flash Row Select Register
The Flash Row Select Register is a 3-bit value used to define one of the 8 rows of Flash
on a single page. This register is used for all I/O access to Flash memory. In addition,
each access to the FLASH_DATA register causes an autoincrement of the Flash address
stored in the Flash Address registers (FLASH_PAGE, FLASH_ROW, FLASH_COL).
See Table 44.
Table 44. Flash Row Select Register (FLASH_ROW = 00FDh)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
0
0
0
CPU Access
R
R
R
R
R
R/W
R/W
R/W
Note: R/W = Read/Write, R = Read Only.
Bit 
Position
Value Description
[7:3]
00h
Reserved.
[2:0]
0h–7h Row address of Flash memory to be used during an I/O access
FLASH_ROW
of Flash memory. When INFO_EN is 1 in the Flash Page Select
Register, values for this field are restricted to 0h–1h, which
selects between the two rows in the information page.
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
112
Flash Column Select Register
The Flash Column Select Register is an 8-bit value used to define one of the 256 bytes of
Flash memory contained in a single row. This register is used for all I/O access to Flash
memory. In addition, each access to the FLASH_DATA register causes an autoincrement
of the Flash address stored in the Flash Address registers (FLASH_PAGE, FLASH_ROW,
FLASH_COL). See Table 45.
Table 45. Flash Column Select Register (FLASH_COL = 00FEh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write, R = Read Only.
Bit 
Position
Value
[7:0]
FLASH_COL
00h–FFh Column address of Flash memory to be used during an I/O
access of Flash memory.
Description
Flash Program Control Register
The Flash Program Control Register is used to perform the functions of MASS ERASE,
PAGE ERASE, and ROW PROGRAM. MASS ERASE and PAGE ERASE are 
self-clearing functions.
MASS ERASE requires approximately 200 ms to completely erase the full 256 KB of
main Flash and the 512-byte information page if the FLASH_PAGE register(0x00FC)
bit7(INFO_EN) is set. The 200 ms time is not reduced by excluding the 512 byte
information page from erasing.
PAGE ERASE requires approximately 10 ms to erase a 2 KB page.
On completion of either a MASS ERASE or PAGE ERASE, the value of each 
corresponding bit is reset to 0.
When Flash is being erased, any Read or Write access to Flash forces the CPU into a Wait
state until the Erase operation is complete and the Flash is accessed. Reads and Writes to
areas other than Flash memory proceeds as usual while an Erase operation is 
underway.
During row programming, any reads of Flash memory force a WAIT condition until the
row programming operation completes or times out. See Table 46 on page 113.
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
113
Table 46. Flash Program Control Register (FLASH_PGCTL = 00FFh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R/W
R/W
R/W
Note: R/W = Read/Write, R = Read Only.
PS019215-0910
Bit 
Position
Value Description
[7:3]
00h
Reserved.
[2]
ROW_PGM
0
Row Program Disable or Row Program completed.
1
Row Program Enable. This bit automatically resets to 0 when
the row address reaches 256 or when the Row Program
operation times out.
[1]
PG_ERASE
0
Page Erase Disable (Page Erase completed).
1
Page Erase Enable. This bit automatically resets to 0 when the
PAGE ERASE operation is complete.
[0]
MASS_ERASE
0
Mass Erase Disable (Mass Erase completed).
1
Mass Erase Enable. This bit automatically resets to 0 when the
MASS ERASE operation is complete.
Flash Memory
eZ80F91 MCU
Product Specification
114
PS019215-0910
Flash Memory
eZ80F91 MCU
Product Specification
115
Watchdog Timer
The Watchdog Timer (WDT) helps protect against corrupt or unreliable software, power
faults, and other system-level problems which places the CPU into unsuitable operating
states. The eZ80F91 WDT features:
•
Four programmable time-out ranges (depending on the WDT clock source). The four
ranges are:
– 03.2–5.20 ms
– 51.2–83.9 ms
– 0.50–0.82 sec
– 2.68–4.00 sec
•
Three selectable WDT clock sources:
– Internal RC oscillator
– System clock
– Real-Time Clock source (on-chip 32 kHz crystal oscillator or 50/60 Hz signal)
•
A selectable time-out response: a time-out is configured to generate either a RESET or
a nonmaskable interrupt (NMI)
•
A WDT time-out RESET indicator flag
Figure 25 displays a block diagram of the Watchdog Timer.
Data[7:0]
Control Register/
Reset Register
WDT_CLK
RTC Clock
System Clock
WDT
Oscillator
28-Bit
Upcounter
WDT Control Logic
Time-out Compare Logic
(WDT_PERIOD)
RESET
¤
NMI to eZ80 CPU
Figure 25. Watchdog Timer Block Diagram
PS019215-0910
Watchdog Timer
eZ80F91 MCU
Product Specification
116
Watchdog Timer Operation
Enabling and Disabling the Watchdog Timer
The WDT is disabled on a RESET. To enable the WDT, the application program must set
WDT_EN, which is bit 7 of the WDT_CTL register. After WDT_EN is set, no Writes are
allowed to the WDT_CTL register. When enabled, the WDT cannot be disabled except by
a RESET.
Time-Out Period Selection
There are four choices of time-out periods for the WDT. The WDT time-out period is
defined by the WDT_PERIOD WDT_CTL[1:0] field and WDT_CLK WDT_CTL[3:2]
field of the Watchdog Timer control register (WDT_CTL = 0093h). The approximate
time-out period and corresponding clock cycles for three different WDT clock sources are
listed in Table 47.
The WDT time-out period divider is set to one of the four available settings for the
selected frequency of the WDT clock source. Basing the divider settings on the clock
source values provides a time-out range from few seconds to few msecs, regardless of the
frequency setting.
Table 47. WDT Approximate Time-Out Delays for Possible Clock Sources
00
01
10
11
50 MHz system
clock
32.768 kHz RTC
clock
Internal RC
oscillator (~10
kHz)
Reserved
WDT_CLK[
3:2]
WDT_PERI
OD[1:0]
Divider Timeout
Divider
Timeout Divider Timeout Divider Timeout
00
227
2.68 s
217
4.00 s
215
3.28 s
-
-
01
225
0.67 s
214
0.5 s
213
0.82 s
-
-
10
2
22
51.2 ms
-
-
11
218
3.2 ms
-
-
11
83.9 ms
2
5.2 ms
27
9
62.5 ms
2
3.9 ms
25
RESET or NMI Generation
A WDT time-out causes a RESET or sends a NMI signal to the CPU. The default operation is for the WDT to cause a RESET.
If the NMI_OUT bit in the WDT_CTL register is set to 0, then on a WDT time-out, the
RST_FLAG bit in the WDT_CTL register is set to 1. The RST_FLAG bit is polled by the
CPU to determine the source of the RESET event.
PS019215-0910
Watchdog Timer
eZ80F91 MCU
Product Specification
117
If the NMI_OUT bit in the WDT_CTL register is set to 1, then on time-out, the WDT
asserts an NMI for CPU processing. The NMI_FLAG bit is polled by the CPU to determine the source of the NMI event.
Watchdog Timer Registers
Watchdog Timer Control Register
The Watchdog Timer Control register (see Table 48) is an 8-bit Read/Write register used to
enable the Watchdog Timer, set the time-out period, indicate the source of the most recent
RESET or NMI, and select the required operation on WDT time-out.
The default clock source for the WDT is the WDT oscillator (WDT_CLK = 10b). 
To power-down the WDT oscillator, another clock source must be selected. The powerup sequence of the WDT oscillator takes approximately 20 ms.
Table 48. Watchdog Timer Control Register (WDT_CTL = 0093h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0/1
0
1
0
0
0
R/W
R/W
R
R
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
Bit
Position
PS019215-0910
Value Description
7
WDT_EN
0
WDT is disabled.
1
WDT is enabled. When enabled, the WDT cannot be disabled
without a RESET.
6
NMI_OUT
0
WDT time-out resets the CPU.
1
WDT time-out generates a NMI to the CPU.
5
RST_FLAG
0
RESET caused by external full-chip reset or ZDI reset.
1
RESET caused by WDT time-out. This flag is set by the WDT
time-out, only if the NMI_OUT flag is set to 0. The CPU polls
this bit to determine the source of the RESET. This flag is
cleared by a non-WDT generated reset.
4
NMI_FLAG
0
NMI caused by external source.
1
NMI caused by WDT time-out. This flag is set by the WDT timeout, only if the NMI_OUT flag is set to 1. The CPU polls this bit
to determine the source of the NMI. This flag is cleared by a
non-WDT NMI.
Watchdog Timer
eZ80F91 MCU
Product Specification
118
Bit
Position
[3:2]
WDT_CLK
[1:0]
WDT_PERIOD
Value Description
00
WDT clock source is system clock.
01
WDT clock source is Real-Time Clock source (32 kHz on-chip
oscillator or 50/60 Hz input as set by RTC_CTRL[4]).
10
WDT clock source is internal RC oscillator (10 kHz typical).
11
Reserved.
00
WDT_CLK = 00 WDT time-out period is 227 clock cycles.
WDT_CLK = 01 WDT time-out period is 217 clock cycles.
WDT_CLK = 10 WDT time-out period is 215 clock cycles.
WDT_CLK = 11 Reserved.
01
WDT_CLK = 00 WDT time-out period is 225 clock cycles.
WDT_CLK = 01 WDT time-out period is 214 clock cycles.
WDT_CLK = 10 WDT time-out period is 213 clock cycles.
WDT_CLK = 11 Reserved.
10
WDT_CLK = 00 WDT time-out period is 222 clock cycles.
WDT_CLK = 01 WDT time-out period is 211 clock cycles.
WDT_CLK = 10 WDT time-out period is 29 clock cycles.
WDT_CLK = 11 Reserved.
11
WDT_CLK = 00 WDT time-out period is 218 clock cycles.
WDT_CLK = 01 WDT time-out period is 27 clock cycles.
WDT_CLK = 10 WDT time-out period is 25 clock cycles.
WDT_CLK = 11 Reserved.
Note: When the WDT is enabled, no Writes are allowed to the WDT_CTL register.
PS019215-0910
Watchdog Timer
eZ80F91 MCU
Product Specification
119
Watchdog Timer Reset Register
The WDT Reset register (see Table 49) is an 8-bit Write only register. The WDT is reset
when an A5h value followed by a 5Ah value is written to this register. Any amount of time
occurs between the writing of A5h value and the 5Ah value, so long as the WDT time-out
does not occur prior to completion. Any value other than 5Ah written to the WDT Reset
register after the A5h value requires that the sequence of Writes (A5h,5Ah) be restarted for
the timer to be reset.
Table 49. Watchdog Timer Reset Register (WDT_RR = 0094h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: X = Undefined; W = Write Only.
Bit
Position
[7:0]
WDT_RR
PS019215-0910
Value Description
A5h
The first Write value required to reset the WDT prior to a timeout.
5Ah
The second Write value required to reset the WDT prior to a
time-out. If an A5h, 5Ah sequence is written to WDT_RR, the
WDT timer is reset to its initial count value and counting
resumes.
Watchdog Timer
eZ80F91 MCU
Product Specification
120
PS019215-0910
Watchdog Timer
eZ80F91 MCU
Product Specification
121
Programmable Reload Timers
The eZ80F91 device features four programmable reload timers. The core of each timer is a
16-bit downcounter. In addition, each timer features a selectable clock source, adjustable
prescaling and operates in either SINGLE PASS or CONTINUOUS mode.
In addition to the basic timer functionality, some of the timers support specialty modes
that performs event counting, input capture, output compare, and Pulse-Width Modulation
(PWM) generation functions. PWM mode supports four individually-configurable outputs
and a power trip function.
Each of the four timers available on the eZ80F91 device are controlled individually. They
do not share the same counters, reload registers, control registers, or interrupt signals. A
simplified block diagram of a programmable reload timer is displayed in Figure 26.
Each timer features its own interrupt which is triggered either by the timer reaching zero
or after a successful comparison occurs. As with the other eZ80F91 interrupts, the priority
is fully programmable.
Input Capture
Registers
CONTROL
R
E
L
O
A
D
16-Bit
Down Counter
ICx
Comparator
OCx
16
16
DIV
SCLK
Output Compare
Registers
M
U
X
RTC CLK
ECx
EOC
IC
OC
PWM
PWR Trip
PWM
Control
PWM
IRQ Control
IRQ
Figure 26. Programmable Reload Timer Block Diagram
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
122
Basic Timer Operation
Basic timer operation is controlled by a timer control register and a programmable reload
value. The CPU uses the control register to setup the prescaling, the input clock source,
the end-of-count behavior, and to start the timer. The 16-bit reload value is used to 
determine the duration of the timer’s count before either halting or reloading.
After choosing a timer period and writing the appropriate values to the reload registers, the
CPU must set the timer enable bit (TMRx_CTL[TIM_EN]) by allowing the count to
begin. The reload bit (TMRx_CTL[RLD]) must also be asserted so that the timer counts
down from the reload value rather than from 0000h. On the system clock cycle, after the
assertion of the reload bit, the timer loads with the 16-bit reload value and begins counting
down. The reload bit is automatically cleared after the loading operation. The timer is
enabled and reloaded on the same cycle; however, the timer does not require disabling to
reload and reloading is performed at any time. It is also possible to halt the timer by deasserting the timer enable bit and resuming the count at a later time from the same point by
reasserting the bit.
Reading the Current Count Value
The CPU reads the current count value when the timer is running. Because the count is a
16-bit value, the hardware latches the value of the upper byte into temporary storage when
the lower byte is read. This value in temporary storage is the value returned when the
upper byte is read. Therefore, the software must read the lower byte first. If it attempts to
read the upper byte first, it does not obtain the current upper byte of the count. Instead, it
obtains the last latched value. This Read operation does not affect timer operation.
Setting Timer Duration
There are three factors to consider while determining Programmable Reload Timer 
duration: clock frequency, clock divider ratio, and initial count value. Minimum duration
of the timer is achieved by loading 0001h. Maximum duration is achieved by loading
0000h, because the timer first rolls over to FFFFh and then continues counting down to
0000h before the end-of-count is signaled. Depending on the TMRx_CTL[CLK_SEL]
bits of the control register, the clock is either the system clock, or an on-chip RC oscillator
output or an input from a pin.
The time-out period of the timer is returned by the following equation:
Time-Out Period =
Clock Divider Ratio x Reload Value
System Clock Frequency
To calculate the time-out period with the above equation while using an initial value of
0000h, enter a reload value of 65536 (FFFFh + 1).
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
123
Minimum time-out duration is four times longer than the input clock period and is generated by setting the clock divider ratio to 1:4 and the reload value to 0001h. Maximum
time-out duration is 224 (16,777,216) times longer than the input clock period and is generated by setting the clock divider ratio to 1:256 and the reload value to 0000h.
SINGLE PASS Mode
In SINGLE PASS mode when the end-of-count value (0000h) is reached; counting halts,
the timer is disabled, and TMRx_CTL[TIM_EN] bit resets to 0. To re-enable the timer, the
CPU must set the TIM_EN bit to 1. An example of a PRT operating in SINGLE PASS
mode is displayed in Figure 27. Timer register information is listed in Table 50.
System Clock
Clock Enable
TMR3_CTL Write
(Timer Enable)
T3 Count
0
4
3
2
1
0
Interrupt Request
Figure 27. Example: PRT SINGLE PASS Mode Operation
Table 50. Example: PRT SINGLE PASS Mode Parameters
Parameter
Control Register(s)
Value
Timer Enable
TMRx_CTL[TIM_EN]
1
Reload
TMRx_CTL[RLD]
1
Prescaler Divider = 4
TMRx_CTL[CLK_DIV]
00b
SINGLE PASS Mode
TMRx_CTL[TIM_CONT]
0
End of Count Interrupt Enable
TMRx_IER[IRQ_EOC_EN]
1
Timer Reload Value
{TMRx_RR_H, TMRx_RR_L}
0004h
CONTINUOUS Mode
In CONTINUOUS mode, when the end-of-count value, 0000h, is reached, the timer
automatically reloads the 16-bit start value from the Timer Reload registers,
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
124
TMRx_RR_H and TMRx_RR_L. Downcounting continues on the next clock edge and
the timer continues to count until disabled. An example of the timer operating in 
CONTINUOUS mode is displayed in Figure 28. Timer register information is listed in
Table 51.
System Clock
Clock Enable
TMR3_CTL Write
(Timer Enable)
T3 Count
X
4
3
2
1
4
3
2
1
Interrupt
Request
Figure 28. Example: PRT CONTINUOUS Mode Operation
Table 51. Example: PRT CONTINUOUS Mode Parameters
Parameter
Control Register(s)
Value
Timer Enable
TMRx_CTL[TIM_EN]
1
Reload
TMRx_CTL[RLD]
1
Prescaler Divider = 4
TMRx_CTL[CLK_DIV]
00b
CONTINUOUS Mode
TMRx_CTL[TIM_CONT]
1
End of Count Interrupt Enable
TMRx_IER[IRQ_EOC_EN]
1
Timer Reload Value
{TMRx_RR_H, TMRx_RR_L}
0004h
Timer Interrupts
The terminal count flag (TMRx_IIR[EOC]) is set to 1 whenever the timer reaches 0000h,
its end-of-count value in SINGLE PASS mode, or when the timer reloads the start value in
CONTINUOUS mode. The terminal count flag is only set when the timer reaches 0000h
(or reloads) from 0001h. The timer interrupt flag is not set to 1 when the timer is loaded
with the value 0000h, which selects the maximum time-out period.
The CPU is programmed to poll the EOC bit for the time-out event. Alternatively, an interrupt service request signal is sent to the CPU by setting the TMRx_IER[EOC] bit to 1.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
125
And when the end-of-count value (0000h) is reached, the EOC bit is set to 1 and an interrupt service request signal is passed to the CPU. The interrupt service request signal is
deactivated by a CPU read of the timer interrupt identification register, TMRx_IIR. 
All bits in that register are reset by the Read.
The response of the CPU to this interrupt service request is a function of the CPU’s interrupt enable flag, IEF1. For more information about this flag, refer to the eZ80® CPU User
Manual (UM0077) available on www.zilog.com.
Timer Input Source Selection
Timers 0–3 features programmable input source selection. By default, the input is taken
from the eZ80F91’s system clock. The timers also use the Real-Time Clock source (50,
60, or 32768 Hz) as their clock sources. The input source for these timers is set using the
timer control register. (TMRx_CTL[CLK_SEL])
Timer Output
The timer count is directed to the GPIO output pins, if required. To enable the Timer 
Output feature, the GPIO port pin must be configured as an output and for alternate functions. The GPIO output pin toggles each time the timer reaches its end-of-count value. 
In CONTINUOUS mode operation, enabling the Timer Output feature results in a Timer
Output signal period which is twice the timer time-out period. Examples of Timer Output
operation is displayed in Figure 29 on page 126 and listed in Table 52 on page 126. The
initial value for the timer output is zero.
Logic to support timer output exists in all timers; but for the eZ80F91 device, only Timer
0 and 2 route the actual timer output to the pins. Because Timer 3 uses the TOUT pins for
PWMxN signals, the timer outputs are not available when using complementary PWM
outputs. See Table 52 on page 126 for details.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
126
Break Point Halting
System Clock
Clock Enable
TMR3_CTL Write
(Timer Enable)
T3 Count
0
4
3
2
1
4
3
2
1
Timer Out
(internal)
Timer Out
(at pad)
Figure 29. Example: PRT Timer Output Operation
Table 52. Example: PRT Timer Out Parameters
Parameter
Control Register(s)
Value
Timer Enable
TMRx_CTL[TIM_EN]
1
Reload
TMRx_CTL[RLD]
1
Prescaler Divider = 4
TMRx_CTL[CLK_DIV]
00b
CONTINUOUS Mode
TMRx_CTL[TIM_CONT]
1
Timer Reload Value
{TMRx_RR_H, TMRx_RR_L}
0003h
When the eZ80F91 device is running in DEBUG mode, encountering a break point causes
all CPU functions to halt. However, the timers keep running. This instance makes debugging timer-related software much more difficult. Therefore, the control
register contains a BRK_STP bit. Setting this bit causes the count value to be held during
debug break points.
Specialty Timer Modes
The features described above are common to all timers in the eZ80F91 device. In addition
to these common features, some of the timers have additional functionality.
The following is a list of the special features for each timer:
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
127
•
Timer 0
– No special functions
•
Timer 1
– One event counter (EC0)
– Two input captures (IC0 and IC1)
•
Timer 2
– One event counter (EC1)
•
Timer 3
– Two input captures (IC2 and IC3)
– Four output compares (OC0, OC1, OC2, and OC3)
– Four PWM outputs (PWM0, PWM1, PWM2, and PWM3)
Timer 3 consists of three specialty modes. Each of these modes are enabled using bits in
their respective control registers (TMR3_CAP_CTL, TMR3_OC_CTL1,
TMR3_PWM_CTL1). When PWM mode is enabled, the OUTPUT COMPARE and
INPUT CAPTURE modes are not available. This instance is due to address space sharing
requirements. However, INPUT CAPTURE and OUTPUT COMPARE modes run 
simultaneously.
Timers with specialty modes offer multiple ways to generate an interrupt. When the interrupt controller services a timer interrupt, the software must read the timers interrupt identification register (TMRx_IIR) to determine the causes for an interrupt request. This
register is cleared each time it is read, allowing subsequent events to be identified without
interference from prior events.
Event Counter
When a timer is configured to take its input from a port input pin (ECx), it functions as an
event counter. For event counting, the clock prescaler is automatically bypassed and edges
(events) cause the timer to decrement. You must select the rising or the falling edge for
counting. Also, the port pins must be configured as inputs.
Input sampling on the port pins results in the counter being updated on the third rising
edge of the system clock after the edge event occurs at the port pin. Due to sampling, the
frequency of the event input is limited to one-half the system clock frequency under ideal
conditions. In practice, the event frequency must be less than this value due to duty cycle
variation and system clock jitter.
This EVENT COUNT mode is identical to basic timer operation, except for the clock
source. Therefore, interrupts are managed in the same manner.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
128
RTC Oscillator Input
When the timer clock source is the Real-Time Clock (RTC) signal, the timer functions just
as it does in EVENT COUNT mode, except that it samples the internal RTC clock rather
than the ECx pin.
Input Capture
INPUT CAPTURE mode allows the CPU to determine the timing of specified events on a
set of external pins.
A timer intended for use in INPUT CAPTURE mode is setup the same way as in BASIC
mode, with one exception. The CPU must also write the TMRx_CAP_CTL register to
select the edge on which to capture: rising, falling, or both. When one of these events
occurs on an input capture pin, the current 16 bit timer value is latched into the capture
value register pair (TMRx_CAP_A or TMRx_CAP_B depending on the IC pin exhibiting
the event).
Reading the Low byte of the register pair causes the timer to ignore other capture events
on the associated external pin until the High byte is read. This instance prevents a 
subsequent capture event from overwriting the High byte between the two Reads and 
generating an invalid capture value. The capture value registers are Read Only.
A capture flag (ICA or ICB) in the TMRx_IIR register is set whenever a capture event
occurs. Setting the interrupt identification register bit TMRx_IER[IRQ_ICx_EN] enables
the capture event to generate a timer interrupt. The port pins must be configured as 
alternate functions, see GPIO Mode 7—Alternate Functions on page 51.
Output Compare
The output compare function reverses the input capture function. Rather than store a timer
value when an external event occurs, OUTPUT COMPARE mode waits until the timer
reaches a specified value, then generates an external event. Although the same base timer
is used, up to four separate external pins are driven each with its own compare value.
To use OUTPUT COMPARE mode, the CPU must first configure the basic timer 
parameters. Then it must load up to four 16-bit compare values into the four TMR3_OCx
register pairs. Next, it must load the TMR3_ OC_CTL2 register to specify the event that
occurs on comparison. You can select the following events: SET, CLEAR, and TOGGLE.
Finally, the CPU must enable OUTPUT COMPARE mode by asserting
TMR3_OC_CTL1[OC_EN].
The initial value for the OCx pins in OUTPUT COMPARE mode is 0 by default. It is 
possible to initialize this value to 1 or force a value at a later time. Setting the
TMR3_OC_CTL2[OCx_MODE] value to 0 forces the OCx pin to the selected state 
provided by the TMR3_OC_CTL1[OCx_INIT] bits. Regardless of any compare events,
the pin stays at the forced value until OCx_MODE is changed. After release, it retains the
forced value until modified by an OUTPUT COMPARE event.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
129
Asserting TMR3_OC_CTL1[MAST_MODE] selects MASTER MODE for all OUTPUT
COMPARE events and sets output 0 as the master. As a result, outputs 1, 2, and 3 are
caused to disregard output-specific configuration and comparison values and instead
mimic the current settings for output 0.
The OCx bits in the TMR3_IIR register are set whenever the corresponding timer compares occur. TMR3_IER[IRQ_OCx_EN] allows the compare event to generate a timer
interrupt.
Timer Port Pin Allocation
The eZ80F91 device timers interface to the outside world via Ports A and B. These
ports are also used for GPIO as well as other assorted functions. Table 53 on page 129
lists the timer pins and their respective functions.
Table 53. GPIO Mode Selection Using Timer Pins
Timer Function
Port
GPIO Port
Bits
GPIO Port
Mode
PWM_CTL1
MPWM_EN = 0
PWM_CTL1
MPWM_EN = 1
A
PA0
7
OC0
PWM0
PA1
7
OC1
PWM1
PA2
7
OC2
PWM2
PA3
7
OC3
PWM3
PWM_CTL1
PAIR_EN = 0
PWM_CTL1
PAIR_EN = 1
B
PS019215-0910
PA4
7
TOUT0
PWM0
PA5
7
TOUT2
PWM1
PA6
7
EC1
PWM2
PA7
7
PB0
7
IC0/EC0
PB1
7
IC1
PB4
7
IC2
PB5
7
IC3
PWM3
Programmable Reload Timers
eZ80F91 MCU
Product Specification
130
Timer Registers
The CPU monitors and controls the timer using seven 8-bit registers. These registers are
the control register, the interrupt identification register, the interrupt enable register and
the reload register pair (High and Low byte). There are also a pair of data registers used to
read the current timer count value.
The variable x can be 0, 1, 2, or 3 to represent each of the four available timers.
Basic Timer Register Set
Each timer requires a different set of registers for configuration and control. However,
all timers contain the following seven registers, each of which is necessary for basic 
operation:
•
•
•
•
•
Timer Control Register (TMRx_CTL)
Interrupt Identification Register (TMRx_IIR)
Interrupt Enable Register (TMRx_IER)
Timer Data Registers (TMRx_DR_H and TMRx_DR_L)
Timer Reload Registers (TMRx_RR_H and TMRx_RR_L)
The Timer Data Register is Read Only, when the Timer Reload Register is Write Only.
The address space for these two registers is shared.
Register Set for Capture in Timer 1
In addition to the basic register set, Timer 1 uses the following five registers for its INPUT
CAPTURE mode:
•
•
Capture Control Register (TMR1_CAP_CTL)
Capture Value Registers (TMR1_CAP_B_H, TMR1_CAP_B_L, TMR1_CAP_A_H,
TMR1_CAP_A_L)
Register Set for Capture/Compare/PWM in Timer 3
In addition to the basic register set, Timer 3 uses 19 registers for INPUT CAPTURE,
OUTPUT COMPARE, and PWM modes. PWM and capture/compare functions cannot be
used simultaneously so, their register address space is shared. INPUT CAPTURE and
OUTPUT COMPARE are used concurrently and their address space is not shared.
The INPUT CAPTURE mode registers are equivalent to those used in Timer 1 above
(substitute TMR3 for TMR1).
OUTPUT COMPARE mode uses the following nine registers:
•
PS019215-0910
Output Compare Control Registers
– TMR3_OC_CTL1
Programmable Reload Timers
eZ80F91 MCU
Product Specification
131
–
•
TMR3_OC_CTL2
Compare Value Registers
– TMR3_OC3_H
– TMR3_OC3_L
– TMR3_OC2_H
– TMR3_OC2_L
– TMR3_OC1_H
– TMR3_OC1_L
– TMR3_OC0_H
– TMR3_OC0_L
Multiple PWM mode uses the following 19 registers:
PS019215-0910
•
PWM Control Registers
– TMR3_PWM_CTL1
– TMR3_PWM_CTL2
– TMR3_PWM_CTL3
•
PWM Rising Edge Values
– TMR3_PWM3R_H
– TMR3_PWM3R_L
– TMR3_PWM2R_H
– TMR3_PWM2R_L
– TMR3_PWM1R_H
– TMRx_PWM1R_L
– TMR3_PWM0R_H
– TMR3_PWM0R_L
•
PWM Falling Edge Values
– TMR3_PWM3F_H
– TMRx_PWM3F_L
– TMR3_PWM2F_H
– TMR3_PWM2F_L
– TMR3_PWM1F_H
– TMR3_PWM1F_L
– TMR3_PWM0F_H
– TMR3_PWM0F_L
Programmable Reload Timers
eZ80F91 MCU
Product Specification
132
Timer Control Register
The Timer x Control Register (see Table 54) is used to control timer operations including
enabling the timer, selecting the clock source, selecting the clock divider, selecting
between CONTINUOUS and SINGLEPASS modes, and enabling the auto-reload 
feature.
Table 54. Timer Control Register (TMR0_CTL = 0060h, TMR1_CTL = 0065h,
TMR2_CTL = 006Fh, TMR3_CTL = 0074h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
Bit
Position
Value
0
7
BRK_STOP 1
[6:5]
CLK_SEL
[4:3]
CLK_DIV
The timer continues to operate during debug break points.
The timer stops operation and holds count value during debug
break points.
00
Timer source is the system clock divided by the prescaler.
01
Timer source is the Real Time Clock Input.
10
Timer source is the Event Count (ECx) input—falling edge.
For Timer 1 this is EC0.
For Timer 2, this is EC1.
11
Timer source is the Event Count (ECx) input—rising edge.
For Timer 1 this is EC0.
For Timer 2, this is EC1.
00
System clock divider = 4.
01
System clock divider = 16.
10
System clock divider = 64.
11
System clock divider = 256.
0
The timer operates in SINGLE PASS mode. TIM_EN (bit 0) is
reset to 0 and counting stops when the end-of-count value is
reached.
1
The timer operates in CONTINUOUS mode. The timer reload
value is written to the counter when the end-of-count value is
reached.
2
TIM_CONT
PS019215-0910
Description
Programmable Reload Timers
eZ80F91 MCU
Product Specification
133
1
RLD
0
TIM_EN
0
Reload function is not forced.
1
Force reload. When 1 is written to this bit, the values in the
reload registers are loaded into the downcounter.
0
The programmable reload timer is disabled.
1
The programmable reload timer is enabled.
Timer Interrupt Enable Register
The Timer x Interrupt Enable Register (see Table 55) is used to control timer interrupt
operations. Only bits related to functions present in a given timer are active.
Table 55. Timer Interrupt Enable (TMR0_IER = 0061h, TMR1_IER = 0066h,
TMR2_IER = 0070h, TMR3_IER = 0075h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
Bit
Position
Value
Description
7
0
Unused.
0
Interrupt requests for OC3 are disabled (valid only in
OUTPUT COMPARE mode). OC operations occur in Timer 3.
1
Interrupt requests for OC3 are enabled (valid only in OUTPUT
COMPARE mode). OC operations occur in Timer 3.
0
Interrupt requests for OC2 are disabled (valid only in
OUTPUT COMPARE mode). OC operations occur in Timer 3.
1
Interrupt requests for OC2 are enabled (valid only in OUTPUT
COMPARE mode). OC operations occur in Timer 3.
0
Interrupt requests for OC1 are disabled (valid only in
OUTPUT COMPARE mode). OC operations occur in Timer 3.
1
Interrupt requests for OC1 are enabled (valid only in OUTPUT
COMPARE mode). OC operations occur in Timer 3.
0
Interrupt requests for OC0 are disabled (valid only in
OUTPUT COMPARE mode). OC operations occur in Timer 3.
1
Interrupt requests for OC0 are enabled (valid only in OUTPUT
COMPARE mode). OC operations occur in Timer 3.
6
IRQ_OC3_EN
5
IRQ_OC2_EN
4
IRQ_OC1_EN
3
IRQ_OC0_EN
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
134
0
Interrupt requests for ICx are disabled (valid only in INPUT
CAPTURE mode).
Timer 1: the capture pin is IC1.
Timer 3: the capture pin is IC3.
1
Interrupt requests for ICx are enabled (valid only in INPUT
CAPTURE mode).
For Timer 1: the capture pin is IC1.
For Timer 3: the capture pin is IC3.
0
Interrupt requests for ICA or PWM power trip are disabled
(valid only in INPUT CAPTURE and PWM modes).
For Timer 1: the capture pin is IC0.
For Timer 3: the capture pin is IC2.
1
Interrupt requests for ICA or PWM power trip are enabled
(valid only in INPUT CAPTURE and PWM modes).
For Timer 1: the capture pin is IC0.
For Timer 3: the capture pin is IC2.
2
IRQ_ICB_EN
1
IRQ_ICA_EN
0
0
IRQ_EOC_EN 1
PS019215-0910
Interrupt on end-of-count is disabled.
Interrupt on end-of-count is enabled.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
135
Timer Interrupt Identification Register
The TImer x Interrupt Identification Register (see Table 56) is used to flag timer events so
that the CPU determines the cause of a timer interrupt. This register is cleared by a CPU
Read.
Table 56. Timer Interrupt Identification Register (TMR0_IIR = 0062h, TMR1_IIR =
0067h, TMR2_IIR = 0071h, TMR3_IIR = 0076h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only;
Bit
Position
Value
Description
7
0
Unused.
6
OC3
0
Output compare, OC3, does not occur.
1
Output compare, OC3, occurs.
5
OC2
0
Output compare, OC2, does not occur.
1
Output compare, OC2, occurs.
4
OC1
0
Output compare, OC1, does not occur.
1
Output compare, OC1, occurs.
3
OC0
0
Output compare, OC0, does not occur.
1
Output compare, OC0, occurs.
0
Input capture, ICB, does not occur.
For Timer 1, the capture pin is IC1.
For Timer 3, the capture pin is IC3.
1
Input capture, ICB, occurs.
For Timer 1, the capture pin is IC1.
For Timer 3, the capture pin is IC3.
0
Input capture, ICA, or PWM power trip does not occur.
For Timer 1, the capture pin is IC0.
For Timer 3, the capture pin is IC2.
1
Input capture, ICA, or PWM power trip occurs.
For Timer 1, the capture pin is IC0.
For Timer 3, the capture pin is IC2.
0
End-of-count does not occur.
1
End-of-count occurs.
2
ICB
1
ICA
0
EOC
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
136
Timer Data Register—Low Byte
The Timer x Data Register—Low Byte returns the Low byte of the current count value of
the selected timer. The Timer Data Register—Low Byte (see Table 57) is read when the
timer is in operation. Reading the current count value does not affect timer 
operation. To read the 16-bit data of the current count value, {TMRx_DR_H[7:0],
TMRx_DR_L[7:0]}, first read the Timer Data Register—Low Byte, followed by the
Timer Data Register—High Byte. The Timer Data Register—High Byte value is latched
into temporary storage when a Read of the Timer Data Register—Low Byte occurs.
This register shares its address with the corresponding timer reload register.
Table 57. Timer Data Register—Low Byte (TMR0_DR_L = 0063h, TMR1_DR_L =
0068h, TMR2_DR_L = 0072h, TMR3_DR_L = 0077h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit
Position
[7:0]
TMR_DR_L
PS019215-0910
Value
Description
These bits represent the Low byte of the 2-byte timer data
value, {TMRx_DR_H[7:0], TMRx_DR_L[7:0]}. Bit 7 is bit 7
00h–FFh
of the 16-bit timer data value. Bit 0 is bit 0 (lsb) of the 16-bit
timer data value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
137
Timer Data Register—High Byte
The Timer x Data Register—High Byte returns the High byte of the count value of the
selected timer as it existed at the time that the Low byte was read. The Timer Data 
Register—High Byte (see Table 58) is read when the timer is in operation. Reading the
current count value does not affect timer operation. To read the 16-bit data of the 
current count value, {TMRx_DR_H[7:0], TMRx_DR_L[7:0]}, first read the Timer Data
Register—Low Byte followed by the Timer Data Register—High Byte. The Timer Data
Register—High Byte value is latched into temporary storage when a Read of the Timer
Data Register—Low Byte occurs.
This register shares its address with the corresponding timer reload register.
Table 58. Timer Data Register—High Byte (TMR0_DR_H = 0064h, TMR1_DR_H =
0069h, TMR2_DR_H = 0073h, TMR3_DR_H = 0078h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit
Position
[7:0]
TMR_DR_H
PS019215-0910
Value
Description
These bits represent the High byte of the 2-byte timer data
value, {TMRx_DR_H[7:0], TMRx_DR_L[7:0]}. Bit 7 is bit 15
00h–FFh
(msb) of the 16-bit timer data value. Bit 0 is bit 8 of the 16-bit
timer data value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
138
Timer Reload Register—Low Byte
The Timer x Reload Register—Low Byte (see Table 59) stores the least-significant byte
(LSB) of the 2-byte timer reload value. In CONTINUOUS mode, the timer reload value is
reloaded into the timer on end-of-count. When the reload bit (TMRx_CTL[RLD]) is set to
1 forcing the reload function, the timer reload value is written to the timer on the next rising edge of the clock.
This register shares its address with the corresponding timer data register.
Table 59. Timer Reload Register—Low Byte (TMR0_RR_L = 0063h, TMR1_RR_L
= 0068h, TMR2_RR_L = 0072h, TMR3_RR_L = 0077h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit
Position
[7:0]
TMR_RR_L
PS019215-0910
Value
Description
These bits represent the Low byte of the 2-byte timer
reload value, {TMRx_RR_H[7:0], TMRx_RR_L[7:0]}. Bit 7
00h–FFh
is bit 7 of the 16-bit timer reload value. Bit 0 is bit 0 (lsb) of
the 16-bit timer reload value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
139
Timer Reload Register—High Byte
The Timer x Reload Register—High Byte (see Table 60) stores the most-significant byte
(MSB) of the 2-byte timer reload value. In CONTINUOUS mode, the timer reload value is
reloaded into the timer upon end-of-count. When the reload bit (TMRx_CTL[RLD]) is set
to 1, it forces the reload function, the timer reload value is written to the timer on the next
rising edge of the clock.
This register shares its address with the corresponding timer data register.
Table 60. Timer Reload Register—High Byte (TMR0_RR_H = 0064h,
TMR1_RR_H = 0069h, TMR2_RR_H = 0073h, TMR3_RR_H = 0078h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit
Position
[7:0]
TMR_RR_H
Value
Description
These bits represent the High byte of the 2-byte timer
reload value, {TMRx_RR_H[7:0], TMRx_RR_L[7:0]}. Bit 7
00h–FFh
is bit 15 (msb) of the 16-bit timer reload value. Bit 0 is bit 8
of the 16-bit timer reload value.
Timer Input Capture Control Register
The Timer x Input Capture Control Register (see Table 61) is used to select the edge or
edges to be captured. For Timer 1, CAP_EDGE_B is used for IC1 and CAP_EDGE_A is
for IC0. For Timer 3, CAP_EDGE_B is for IC3, and CAP_EDGE_A is for IC2.
Table 61. Timer Input Capture Control Register 
(TMR1_CAP_CTL = 006Ah, TMR3_CAP_CTL = 007Bh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
PS019215-0910
Bit
Position
Value
Description
[7:4]
0000
Reserved
Programmable Reload Timers
eZ80F91 MCU
Product Specification
140
[3:2]
CAP_EDGE_B
[1:0]
CAP_EDGE_A
00
Disable capture on ICB.
01
Enable capture only on the falling edge of ICB.
10
Enable capture only on the rising edge of ICB.
11
Enable capture on both edges of ICB.
00
Disable capture on ICA.
01
Enable capture only on the falling edge of ICA
10
Enable capture only on the rising edge of ICA.
11
Enable capture on both edges of ICA.
Timer Input Capture Value A Register—Low Byte
The Timer x Input Capture Value A Register—Low Byte (see Table 62) stores the Low
byte of the capture value for external input A. For Timer 1, the external input is IC0. For
Timer 3, it is IC2.
Table 62. Timer Input Capture Value Register A—Low Byte (TMR1_CAPA_L =
006Bh, TMR3_CAPA_L = 007Ch)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit
Position
[7:0]
TMRx_CAPA_L
PS019215-0910
Value
Description
These bits represent the Low byte of the 2-byte capture
value, {TMRx_CAPA_H[7:0], TMRx_CAPA_L[7:0]}. Bit 7 is
00h–FFh
bit 7 of the 16-bit data value. Bit 0 is bit 0 (lsb) of the 16-bit
timer data value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
141
Timer Input Capture Value A Register—High Byte
The Timer x Input Capture Value A Register—High Byte (see Table 63) stores the High
byte of the capture value for external input A. For Timer 1, the external input is IC0. For
Timer 3, it is IC2.
Table 63. Timer Input Capture Value Register A—High Byte (TMR1_CAPA_H
= 006Ch, TMR3_CAPA_H = 007Dh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit
Position
[7:0]
TMRx_CAPA_H
Value
Description
These bits represent the High byte of the 2-byte capture
value, {TMRx_CAPA_H[7:0], TMRx_CAPA_L[7:0]}. Bit 7 is
00h–FFh
bit 15 (msb) of the 16-bit data value. Bit 0 is bit 8 of the 16bit timer data value.
Timer Input Capture Value B Register—Low Byte
The Timer x Input Capture Value B Register—Low Byte (see Table 64) stores the Low
byte of the capture value for external input B. For Timer 1, the external input is IC1. For
Timer 3, it is IC3.
Table 64. Timer Input Capture Value Register B—Low Byte (TMR1_CAPB_L =
006Dh, TMR3_CAPB_L = 007Eh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit
Position
[7:0]
TMRx_CAPB_L
PS019215-0910
Value
Description
These bits represent the Low byte of the 2-byte capture
value, {TMRx_CAPB_H[7:0], TMRx_CAPB_L[7:0]}. Bit 7 is
00h–FFh
bit 7 of the 16-bit data value. Bit 0 is bit 0 (lsb) of the 
16-bit timer data value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
142
Timer Input Capture Value B Register—High Byte
The Timer x Input Capture Value B Register—High Byte (see Table 65) stores the High
byte of the capture value for external input B. For Timer 1, the external input is IC0. For
Timer 3, it is IC3.
Table 65. Timer Input Capture Value Register B—High Byte (TMR1_CAPB_H
= 006Eh, TMR3_CAPB_H = 007Fh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit
Position
[7:0]
TMRx_CAPB_H
Value
Description
These bits represent the High byte of the 2-byte capture
value, {TMRx_CAPB_H[7:0], TMRx_CAPB_L[7:0]}. Bit 7 is
00h–FFh
bit 15 (msb) of the 16-bit data value. Bit 0 is bit 8 of the 16bit timer data value.
Timer Output Compare Control Register 1
The Timer3 Output Compare Control Register 1 (see Table 66) is used to select the Master
Mode and to provide initial values for the OC pins.
Table 66. Timer Output Compare Control Register 1 (TMR3_OC_CTL1 = 0080h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
PS019215-0910
Bit
Position
Value
Description
[7:6]
00
Unused.
5
OC3_INIT
0
OC pin cleared when initialized.
1
OC pin set when initialized.
4
OC2_INIT
0
OC pin cleared when initialized.
1
OC pin set when initialized.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
143
3
OC1_INIT
0
OC pin cleared when initialized.
1
OC pin set when initialized.
2
OC0_INIT
0
OC pin cleared when initialized.
1
OC pin set when initialized.
1
MAST_MODE
0
OC pins are independent.
1
OC pins all mimic OC0.
0
OC_EN
0
OUTPUT COMPARE mode is disabled.
1
OUTPUT COMPARE mode is enabled.
Timer Output Compare Control Register 2
The Timer3 Output Compare Control Register 2 (see Table 67) is used to select the event
that occurs on the output compare pins when a timer compare happens.
Table 67. Timer Output Compare Control Register 2 (TMR3_OC_CTL2 = 0081h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:6]
OC3_MODE
[5:4]
OC2_MODE
PS019215-0910
Value
Description
00
Initialize OC pin to value specified in
TMR3_OC_CTL1[OC3_INT].
01
OC pin is cleared upon timer compare.
10
OC pin is set upon timer compare.
11
OC pin toggles upon timer compare.
00
Initialize OC pin to value specified in
TMR3_OC_CTL1[OC2_INT].
01
OC pin is cleared upon timer compare.
10
OC pin is set upon timer compare.
11
OC pin toggles upon timer compare.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
144
[3:2]
OC1_MODE
[1:0]
OC0_MODE
00
Initialize OC pin to value specified in
TMR3_OC_CTL1[OC1_INT].
01
OC pin is cleared upon timer compare.
10
OC pin is set upon timer compare.
11
OC pin toggles upon timer compare.
00
Initialize OC pin to value specified in
TMR3_OC_CTL1[OC0_INT].
01
OC pin is cleared upon timer compare.
10
OC pin is set upon timer compare.
11
OC pin toggles upon timer compare.
Timer Output Compare Value Register—Low Byte
The Timer3 Output Compare x Value Register—Low Byte (see Table 68) stores the Low
byte of the compare value for OC0–OC3.
Table 68. Compare Value Register—Low Byte (TMR3_OC0_L = 0082h,
TMR3_OC1_L = 0084h, TMR3_OC2_L = 0086h, TMR3_OC3_L = 0088h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
TMR3_OCx_L
PS019215-0910
Value
Description
These bits represent the Low byte of the 2-byte compare
value, {TMR3_OCx_H[7:0], TMR3_OCx_L[7:0]}. Bit 7 is bit
00h–FFh
7 of the 16-bit data value. Bit 0 is bit 0 (lsb) of the 16-bit
timer compare value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
145
Timer Output Compare Value Register—High Byte
The Timer3 Output Compare x Value Register—High Byte (see Table 69) stores the High
byte of the compare value for OC0–OC3.
Table 69. Compare Value Register—High Byte (TMR3_OC0_H = 0083h,
TMR3_OC1_H = 0085h, TMR3_OC2_H = 0087h, TMR3_OC3_H = 0089h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
TMR3_OCx_H
Value
Description
These bits represent the High byte of the 2-byte compare
value, {TMR3_OCx_H[7:0], TMR3_OCx_L[7:0]}. Bit 7 is bit
00h–FFh
15 (msb) of the 16-bit data value. Bit 0 is bit 8
of the 16-bit timer compare value.
Multi-PWM Mode
The special Multi-PWM mode uses the Timer 3 16-bit counter as the primary timekeeper
to control up to four PWM generators. The 16-bit reload value for Timer 3 sets a common
period for each of the PWM signals. However, the duty cycle and phase for each generator
are independent that is, the High and Low periods for each PWM generator are set independently. In addition, each of the four PWM generators are enabled independently. 
The eight PWM signals (four PWM output signals and their inverses) are output via Port
A. A functional block diagram of the Multi-PWM is displayed in Figure 30 on page 146.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
146
16
PWM0
Generator
PWM0 Output
PA4
PWM0 Output
PA1
PWM1 Output
PA5
PWM1 Output
PA2
PWM2 Output
PA6
PWM2 Output
PA3
PWM3 Output
PA7
PWM3 Output
16
Timer 3
16-Bit Binary
Downcounter
PWM1
Generator
16
Timer 3
Clock Input
PA0
Count Value
16
PWM2
Generator
16
PWM3
Generator
Figure 30. Multi-PWM Simplified Block Diagram
Setting TMR3_PWM_CTL1[MPWM_EN] to 1 enables Multi-PWM mode. The
TMR3_PWM_CTL1 register bits enable the four individual PWM generators by adjusting
settings according to the list provided in Table 70.
Table 70. Enabling PWM Generators
Enable PWM generator 0 by setting TMR3_PWM_CTL1[PWM0_EN] to 1.
Enable PWM generator 1 by setting TMR3_PWM_CTL1[PWM1_EN] to 1.
Enable PWM generator 2 by setting TMR3_PWM_CTL1[PWM2_EN] to 1.
Enable PWM generator 3 by setting TMR3_PWM_CTL1[PWM3_EN] to 1.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
147
The inverted PWM outputs PWM0, PWM1, PWM2, and PWM3 are globally enabled by
setting TMR3_PWM_CTL1[PAIR_EN] to 1. The individual PWM generators must be
enabled for the associated inverted PWM signals to be output.
For each of the 4 PWM generators, there is a 16-bit rising edge value
{TMR3_PWMxR_H[PWMxR_H], TMR3_PWMxR_L[PWMxR_L]} and a 16-bit falling
edge value {TMR3_PWMxF_H[PWMxF_H], TMR3_PWMxF_L[PWMxF_L]} for a total
of 16 registers. The rising-edge byte pairs define the timer count at which the PWMx 
output transitions from Low to High. Conversely, the falling-edge byte pairs define the
timer count at which the PWMx output transitions from High to Low. On reset, all enabled
PWM outputs begin Low and all PWMx outputs begin High. When the PWMx output is
Low, the logic is looking for a match between the timer count and the rising edge value,
and vice versa. Therefore, in a case in which the rising edge value is the same as the falling
edge value, the PWM output frequency is one-half the rate at which the counter passes
through its entire count cycle (from reload value down to 0000h).
Figure 31and Figure 32 display a simple Multi-PWM output and an expanded view of the
timing, respectively. Associated control values are listed in Table 71 on page 148.
T3 Count
0
C B A 9 8 7 6 5 4 3 2 1 C B A 9 8 7 6 5 4 3 2 1 C B A 9 8 7 6 5 4 3 2 1 C B A
PWM0
PWM0
PWM1
PWM1
Figure 31. Multi-PWM Operation
System Clock
Clock Enable
T3 Count
A
9
8
7
6
5
4
Figure 32. Multi-PWM Operation—Expanded View of Timing
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
148
Table 71. Example: Multi-PWM Addressing
Parameter
Control Register(s)
Value
Timer Reload Value
{TMR3_RR_H, TMR3_RR_L}
000Ch
PWM0 rising edge
{TMR3_PWM0R_H,
TMR3_PWM0R_L}
0008h
PWM0 falling edge
{TMR3_PWM0F_H, TMR3_PWM0F_L} 0004h
PWM1 rising edge
{TMR3_PWM1R_H,
TMR3_PWM1R_L}
PWM1 falling edge
{TMR3_PWM1F_H, TMR3_PWM1F_L} 0007h
PWM enable
TMR3_PWM_CTL1[PAIR_EN]
1
PWM0 enable
TMR3_PWM_CTL1[PWM0_EN]
1
PWM1 enable
TMR3_PWM_CTL1[PWM1_EN]
1
Multi-PWM enable
TMR3_PWM_CTL1[MPWM_EN]
1
Prescaler Divider = 4
TMR3_CTL[CLK_DIV]
00b
0006h
PWM nonoverlapping delay = 0 TMR3_PWM_CTL2[PWM_DLY]
0000b
PWM Master Mode
In PWM Master mode, the pair of output signals generated from the PWM0 generator
(PWM0 and PWM0) are directed to all four sets of PWM output pairs. Setting
TMR3_PWM_CTL1[MM_EN] to 1 enables PWM Master mode. Assuming the outputs
are all enabled and no AND/OR gating is used, all four PWM output pairs transition
simultaneously under the direction of PWM0 and PWM0. In PWM Master mode, 
the outputs still be gated individually using the AND/OR gating functions described in the
next section. Multi-PWM mode and the individual PWM outputs must be enabled along
with PWM Master mode. It is possible to enable or disable any combination of the four
PWM outputs while running in PWM Master mode.
Modification of Edge Transition Values
Special circuitry is included for the update of the PWM edge transition values. Normal use
requires that these values be updated while the PWM generator is running.
Note:
Under certain circumstances, electric motors driven by the PWM logic encounters rough
operation. In other words, cycles are skipped if the PWM waveform edge is not carefully
modified.
Without special consideration, if a PWM generator looks for a particular count to make a
state transition and if the edge transition value changes to a value that already occurred in
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
149
the current counter count-down cycle, then the transition is missed. The PWM generator
holds the current output state until the counter reloads and cycles through to the 
appropriate edge transition value again. In effect, an entire cycle of the PWM waveform is
skipped with the signal held at a DC value. The change in PWM waveform duty cycle
from cycle to cycle must be limited to some fraction of a period to avoid rough running.
To avoid unintentional roughness due to timing of the load operation for the register values in question, the PWM edge transition values are double-buffered and exhibit the 
following behavior:
•
When the PWM generators are disabled, PWM edge transition values written by the
CPU are immediately loaded into the PWM edge transition registers.
•
When the PWM generators are enabled, a PWM edge transition value is loaded into a
buffer register and transferred to its destination register only during a specific transition
event. A rising edge transition value is only loaded upon a falling edge transition event,
and a falling edge transition value is only loaded upon a rising edge transition event.
AND/OR Gating of the PWM Outputs
When in Multi-PWM mode, it is possible for you to turn off PWM propagation to the pins
without disabling the PWM generator. This feature is global and applies to all enabled
PWM generators. The function is implemented by applying digital logic (AND or OR
functions) to combine the corresponding bits in the port output register with the PWM and
PWM outputs.
The AND or OR functions are enabled on all PWM outputs by setting
TMR3_PWM_CTL2[AO_EN] to either a 01b (AND) or 10b (OR). Any other value 
disables this feature. Likewise, the AND or OR functions are enabled on all PWM outputs
by setting TMR3_PWM_CTL2[AON_EN] to either a 01b (AND) or 10b (OR). Any
other value disables this feature. A functional block diagram for the AND/OR gating feature for PWM0 and PWM0 is displayed in Figure 33 on page 150. The functionality for
the other three PWM pairs are identical.
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
150
00
01
PWM0 Signal
PADR0
PA0
PWM0 Output
PA4
PWM0 Output
10
11
2
TMR3_PWM_CTL2[5:4]
00
01
PWM0 Signal
PADR4
10
11
2
TMR3_PWM_CTL2[7:6]
Figure 33. PWM AND/OR Gating Functional Diagram
If you enable the OR function on all PWM outputs and PADR0 is set to 1, then the PWM0
output on PA0 is forced High. Similarly, if you select the AND function on all PWM 
outputs and PADR0 is set to a 0, then the PWM0 output on PA0 is forced Low.
PWM Nonoverlapping Output Pair Delays
A delay is added between the falling edge of the PWM (PWM) outputs and the rising edge
of the PWM (PWM) outputs. This delay is set to assure that even with load and output
drive variations there will be no overlap between the falling edge of a PWM (PWM) output and the rising edge of its paired output. The selected delay is global to all four PWM
pairs. The delay duration is software-selectable using the 4-bit field
TMR3_PWM_CTL2[PWM_DLY]. The duration is programmable in units of the system
clock (SCLK), from 0 SCLK periods to 15 SCLK periods. The
TMR3_PWM_CTL2[PWM_DLY] bits are mapped directly to a counter, such that a 
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
151
setting of 0000b represents a delay of 0 system clock periods and a setting of 1111b represents a delay of 15 system clock periods. The PWM delay feature is displayed in
Figure 34 with associated addressing listed in Table 72.
The PWM nonoverlapping delay time must always be defined to be less than the delay
between the rising and falling edges (and the delay between the falling and rising edges)
of all Multi-PWM outputs. In other words, a rising (falling) edge cannot be delayed
beyond the time at which it is subsequently scheduled to fall (rise).
Note:
System Clock
Clock Enable
TMR3_Count
A
9
8
7
6
5
4
3
2
1
C
PWM0
PWM0
3 x SCLK
3 x SCLK
Figure 34. PWM Nonoverlapping Output Delay
Table 72. PWM Nonoverlapping Output Addressing
PS019215-0910
Parameter
Control Register(s)
Value
Timer clock is SCLK ÷ 4
TMR3_CTL[CLK_DIV]
00b
Timer reload value
{TMR3_RR_H, TMR3_RR_L}
000Ch
PWM0 rising edge
{TMR3_PWM0R_H, TMR3_PWM0R_L}
0008h
PWM0 falling edge
{TMR3_PWM0F_H, TMR3_PWM0F_L}
0004h
Prescaler divider = 4
TMR3_CTL[CLK_DIV]
00b
PWM nonoverlapping delay = 3
TMR3_PWM_CTL2[PWM_DLY]
0011b
PWM enable
TMR3_PWM_CTL1[PAIR_EN]
1
PWM0 enable
TMR3_PWM_CTL1[PWM0_EN]
1
Multi-PWM enable
TMR3_PWM_CTL1[MPWN_EN]
1
Programmable Reload Timers
eZ80F91 MCU
Product Specification
152
Multi-PWM Power-Trip Mode
When enabled, the Multi-PWM power-trip feature forces the enabled PWM outputs to a
predetermined state when an interrupt is generated from an external source via IC0, IC1,
IC2, or IC3. One or multiple external interrupt sources are enabled at any given time. If
multiple sources are enabled, any of the selected external sources trigger an interrupt.
Configuring the PWM_CTL3 register enables or disables interrupt sources. See Table 75
on page 156.
The possible interrupt sources for a Multi-PWM power-trip are:
•
•
•
•
IC0—digital input
IC1—digital input
IC2—digital input
IC3—digital input
When the power-trip is detected, TMR3_PWM_CTL3[PTD] is set to 1 to indicate 
detection of the power-trip. A value of 0 signifies that no power-trip is detected.
The PWMs are released only after a power-trip when TMR3_PWM_CTL3[PTD] is 
written back to 0 by software. As a result, you are allowed to check the conditions of the
motor being controlled before releasing the PWMs. The explicit release also prevents
noise glitches after a power-trip from causing an accidental exit or re-entry of the PWM
power-trip state.
The programmable power-trip states of the PWMs are globally grouped for the PWM outputs and the inverting PWM outputs. Upon detection of a power-trip, the PWM outputs
are forced to either a High state, a Low state, or high-impedance. The settings for the
power-trip states are made with power-trip control bits TMR3_PWM_CTL3[PT_LVL],
TMR3_PWM_CTL3[PT_LVL_N], and TMR3_PWM_CTL3[PT_TRI].
PS019215-0910
Programmable Reload Timers
eZ80F91 MCU
Product Specification
153
Multi-PWM Control Registers
Pulse-Width Modulation Control Register 1
The PWM Control Register 1 (see Table 73) controls PWM function enables.
Table 73. PWM Control Register 1 (PWM_CTL1 = 0079h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
PS019215-0910
Value
Description
7
PAIR_EN
0
Global disable of the PWM outputs (PWM outputs enabled
only).
1
Global enable of the PWM and PWM output pairs.
6
PT_EN
0
Disable power-trip feature.
1
Enable power-trip feature.
5
MM_EN
0
Disable Master mode.
1
Enable Master mode.
4
pwm3_en
0
Disable PWM generator 3.
1
Enable PWM generator 3.
3
pwm2_en
0
Disable PWM generator 2.
1
Enable PWM generator 2.
2
pwm1_en
0
Disable PWM generator 1.
1
Enable PWM generator 1.
1
PWM0_EN
0
Disable PWM generator 0.
1
Enable PWM generator 0.
0
mpwm_en
0
Disable Multi-PWM mode.
1
Enable Multi-PWM mode.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
154
Pulse-Width Modulation Control Register 2
The PWM Control Register 2 (see Table 74) controls pulse-width modulation AND/OR
and edge delay functions.
Table 74. PWM Control Register 2 (PWM_CTL2 = 007Ah)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:6]
AON_EN
[5:4]
AO_EN
PS019215-0910
Value
Description
00
Disable AND/OR features on PWM
01
Enable AND logic on PWM
10
Enable OR logic on PWM
11
Disable AND/OR features on PWM
00
Disable AND/OR features on PWM
01
Enable AND logic on PWM
10
Enable OR logic on PWM
11
Disable AND/OR features on PWM
Programmable Reload Timers
eZ80F91 MCU
Product Specification
155
[3:0]
PWM_DLY
PS019215-0910
0000
No delay between falling edge of PWM (PWM) and rising
edge of PWM (PWM)
0001
Delay of 1 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
0010
Delay of 2 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
0011
Delay of 3 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
0100
Delay of 4 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
0101
Delay of 5 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
0110
Delay of 6 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
0111
Delay of 7 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1000
Delay of 8 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1001
Delay of 9 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1010
Delay of 10 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1011
Delay of 11 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1100
Delay of 12 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1101
Delay of 13 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1110
Delay of 14 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
1111
Delay of 15 SCLK periods between falling edge of PWM
(PWM) and rising edge of PWM (PWM)
Programmable Reload Timers
eZ80F91 MCU
Product Specification
156
Pulse-Width Modulation Control Register 3
The PWM Control Register 3 (see Table 75) is used to configure the PWM power trip
functionality.
Table 75. PWM Control Register 3 (PWM_CTL3 = 007Bh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
CPU Access
Note: R/W = Read/Write; R = Read only.
Bit
Position
Description
0
7
PT_IC3_EN 1
Power trip disabled on IC3.
0
6
PT_IC2_EN 1
Power trip disabled on IC2.
0
5
PT_IC1_EN 1
Power trip disabled on IC1.
0
4
PT_IC0_EN 1
Power trip disabled on IC0.
Power trip enabled on IC3.
Power trip enabled on IC2.
Power trip enabled on IC1.
Power trip enabled on IC0.
3
PT_TRI
0
All PWM trip levels are open-drain.
1
All PWM trip levels are defined by PT_LVL and PT_LVL_N.
2
PT_LVL
0
After power trip, PWMx outputs are set to one.
1
After power trip, PWMx outputs are set to zero.
1
PT_LVL_N
0
After power trip, PWMx outputs are set to one.
1
After power trip, PWMx outputs are set to zero.
0
Power trip has been cleared.
1
This bit is set after power trip event.
0
PTD
PS019215-0910
Value
Programmable Reload Timers
eZ80F91 MCU
Product Specification
157
Pulse-Width Modulation Rising Edge—Low Byte
A parallel 16-bit Write of {TMR3_PWMxR_H[7–0], TMR3_PWMxR_L[7–0]} occurs
when software initiates a Write to TMR3_PWMxR_L. The register is listed in 
Table 76.
Table 76. PWMx Rising-Edge Register—Low Byte (TMR3_PWM0R_L = 007Ch,
TMR3_PWM1R_L = 007Eh, TMR3_PWM2R_L = 0080h, TMR3_PWM3R_L = 0082h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
PWMXR_L
Value
Description
These bits represent the Low byte of the 16-bit value to set the
rising edge COMPARE value for PWMx,
00h–FFh {TMR3_PWMXR_H[7:0], TMR3_PWMXR_L[7:0]}. Bit 7 is bit 7
of the 16-bit timer data value. Bit 0 is bit 0 (lsb) of the 
16-bit timer data value.
Pulse-Width Modulation Rising Edge—High Byte
Writing to TMR3_PWMxR_H stores the value in a temporary holding register. A parallel
16-bit Write of {TMR3_PWMxR_H[7–0], TMR3_PWMxR_L[7–0]} occurs when software initiates a Write to TMR3_PWMxR_L. The register is listed in Table 77.
Table 77. PWMx Rising-Edge Register—High Byte (TMR3_PWM0R_H = 007Dh,
TMR3_PWM1R_H = 007Fh, TMR3_PWM2R_H = 0081h, TMR3_PWM3R_H = 0083h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
PWMXR_H
PS019215-0910
Value
Description
These bits represent the High byte of the 16-bit value to set the
rising edge COMPARE value for PWMx,
00h–FFh {TMR3_PWMXR_H[7:0], TMR3_PWMXR_L[7:0]}. Bit 7 is bit
15 (msb) of the 16-bit timer data value. Bit 0 is bit 8 of the 
16-bit timer data value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
158
Pulse-Width Modulation Falling Edge—Low Byte
A parallel 16-bit Write of {TMR3_PWMxF_H[7–0], TMR3_PWMxF_L[7–0]} occurs
when software initiates a Write to TMR3_PWMxF_L. The register is listed in Table 78.
Table 78. PWMx Falling-Edge Register—Low Byte (TMR3_PWM0F_L = 0084h,
TMR3_PWM1F_L = 0086h, TMR3_PWM2F_L = 0088h, TMR3_PWM3F_L = 008Ah)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
PWMXF_L
Value
Description
These bits represent the Low byte of the 16-bit value to set the
falling edge COMPARE value for PWMx,
00h–FFh {TMR3_PWMXF_H[7:0], TMR3_PWMXF_L[7:0]}. Bit 7 is bit 7
of the 16-bit timer data value. Bit 0 is bit 0 (lsb) of the 
16-bit timer data value.
Pulse-Width Modulation Falling Edge—High Byte
Writing to TMR3_PWMxF_H stores the value in a temporary holding register. A parallel
16-bit Write of {TMR3_PWMxF_H[7–0], TMR3_PWMxF_L[7–0]} occurs when 
software initiates a Write to TMR3_PWMxF_L. The register is listed in Table 79.
Table 79. PWMx Falling-Edge Register—High Byte (TMR3_PWM0F_H = 0085h,
TMR3_PWM1F_H = 0087h, TMR3_PWM2F_H = 0089h, TMR3_PWM3F_H = 008Bh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
PWMXF_H
PS019215-0910
Value
Description
These bits represent the High byte of the 16-bit value to set the
falling edge COMPARE value for PWMx,
00h–FFh {TMR3_PWMXF_H[7:0], TMR3_PWMXF_L[7:0]}. Bit 7 is bit 15
(msb) of the 16-bit timer data value. Bit 0 is bit 8 of the 
16-bit timer data value.
Programmable Reload Timers
eZ80F91 MCU
Product Specification
159
Real-Time Clock
Real-Time Clock Overview
The Real-Time Clock (RTC) maintains time by keeping count of seconds, minutes, hours,
day-of-the-week, day-of-the-month, year, and century. The current time is kept in 24-hour
format. The format for all count and alarm registers is selectable between binary and
binary-coded-decimal (BCD) operations. The calendar operation maintains the correct
day-of-the-month and automatically compensates for leap year. A simplified block
diagram of the RTC and the associated on-chip, low-power, 32 kHz oscillator is displayed
in Figure 35. Connections to an external battery supply and 32 kHz crystal network is also
displayed in Figure 35.
Note:
For users NOT using the RTC the following RTC signal pins must be connected as follows
to avoid a 10 uA leakage within the RTC circuit block. RTC_Xin (pin 61) must be left floating or connected to ground.
RTC_VDD
Battery
VDD
to eZ80 CPU
IRQ
Real-Time Clock
ADDR[15:0]
DATA[7:0]
R1
RTC_XOUT
RTC Clock
C
System Clock
Low-Power
32 KHz Oscillator
VDD
32 KHz
Crystal
Enable
CLK_SEL
(RTC_CTRL[4])
RTC_XIN
C
Figure 35. Real-Time Clock and 32 kHz Oscillator Block Diagram
PS019215-0910
Real-Time Clock
eZ80F91 MCU
Product Specification
160
Real-Time Clock Alarm
The clock is programmed to generate an alarm condition when the current count matches
the alarm set-point registers. Alarm registers are available for seconds, minutes, hours, and
day-of-the-week. Each alarm is independently enabled. To generate an alarm condition,
the current time must match all enabled alarm values. For example, if the day-of-the-week
and hour alarms are both enabled, the alarm only occurs at a specified hour on a specified
day. The alarm triggers an interrupt if the interrupt enable bit, INT_EN, is set to 1. The
alarm flag, ALARM, and corresponding interrupt to the CPU are cleared by reading the
RTC_CTRL register.
Alarm value registers and alarm control registers are written at any time. Alarm conditions
are generated when the count value matches the alarm value. The comparison of alarm and
count values occurs whenever the RTC count increments (one time every second). The
RTC is also forced to perform a comparison at any time by writing a 0 to the
RTC_UNLOCK bit (the RTC_UNLOCK bit is not required to be changed to a 1 first).
Real-Time Clock Oscillator and Source Selection
The RTC count is driven by either the on-chip 32 kHz RTC oscillator or an external 
50/60 Hz CMOS-level clock signal (typically derived from the AC power line frequency).
The on-chip oscillator requires an external 32 kHz crystal connected to RTC_XIN and
RTC_XOUT as displayed in Figure 35 on page 159. If an external 50/60 Hz clock signal is
used, connect it to RTC_XOUT.
The clock source and power-line frequencies are selected in the RTC_CTRL register.
Writing to the RTC_CTRL register resets the clock divider.
Real-Time Clock Battery Backup
The power supply pin (RTC_VDD) for the RTC and associated low-power 32 kHz 
oscillator is isolated from the other power supply pins on the eZ80F91 device. To ensure
that the RTC continues to keep time in the event of loss of line power to the application, a
battery is used to supply power to the RTC and the oscillator via the RTC_VDD pin. All
VSS (ground) pins must be connected together on the printed circuit assembly.
Real-Time Clock Recommended Operation
Following a initial system reset from a power-down condition of VDD and VDD_RTC, the
counter values of the RTC are undefined and all alarms are disabled. The following procedure is recommended to initialize the Real-Time Clock:
•
PS019215-0910
Write to RTC_CTRL to set RTC_UNLOCK and disable the RTC counter; this action
also clears the clock divider
Real-Time Clock
eZ80F91 MCU
Product Specification
161
•
•
•
Write values to the RTC count registers to set the current time
Write values to the RTC alarm registers to set the appropriate alarm conditions
Write to RTC_CTRL to clear RTC_UNLOCK; clearing the RTC_UNLOCK bit resets
and enables the clock divider
Real-Time Clock Registers
The RTC registers are accessed via the address and data buses using I/O instructions. The
RTC_UNLOCK control bit controls access to the RTC count registers. When unlocked
(RTC_UNLOCK = 1), the RTC count is disabled and the count registers are Read/Write.
When locked (RTC_UNLOCK = 0), the RTC count is enabled and the count registers are
Read Only. The default at RESET is for the RTC to be locked.
Real-Time Clock Seconds Register
This register contains the current seconds count. The value in the RTC_SEC register is
unchanged by a RESET. The current setting of BCD_EN determines whether the values
in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
Access to this register is Read Only if the RTC is locked, and Read/Write if the RTC is
unlocked. See Table 80.
Table 80. Real-Time Clock Seconds Register (RTC_SEC = 00E0h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded-Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TEN_SEC
0–5
The tens digit of the current seconds count.
[3:0]
SEC
0–9
The ones digit of the current seconds count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
SEC
00h–3Bh The current seconds count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
162
Real-Time Clock Minutes Register
This register contains the current minutes count. The value in the RTC_MIN register is 
unchanged by a RESET. The current setting of BCD_EN determines whether the values
in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
Access to this register is Read Only if the RTC is locked, and Read/Write if the RTC is
unlocked. See Table 81.
Table 81. Real-Time Clock Minutes Register (RTC_MIN = 00E1h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TEN_MIN
0–5
The tens digit of the current minutes count.
[3:0]
MIN
0–9
The ones digit of the current minutes count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
MIN
00h–3Bh The current minutes count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
163
Real-Time Clock Hours Register
This register contains the current hours count. The value in the RTC_HRS register is 
unchanged by a RESET. The current setting of BCD_EN determines whether the values
in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
Access to this register is Read Only if the RTC is locked, and Read/Write if the RTC is
unlocked. See Table 82.
Table 82. Real-Time Clock Hours Register (RTC_HRS = 00E2h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TEN_HRS
0–2
The tens digit of the current hours count.
[3:0]
HRS
0–9
The ones digit of the current hours count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
HRS
00h–17h The current hours count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
164
Real-Time Clock Day-of-the-Week Register
This register contains the current day-of-the-week count. The RTC_DOW register begins
counting at 01h. The value in the RTC_DOW register is unchanged by a RESET. The 
current setting of BCD_EN determines whether the value in this register is binary
(BCD_EN = 0) or binary-coded decimal (BCD_EN = 1). Access to this register is Read
Only if the RTC is locked and Read/Write if the RTC is unlocked. See Table 83.
Table 83. Real-Time Clock Day-of-the-Week Register (RTC_DOW = 00E3h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
X
X
X
X
CPU Access
R
R
R
R
R/W*
R/W*
R/W*
R/W*
Note: X = Unchanged by RESET; R = Read Only; R/W* = Read Only if RTC locked, Read/Write 
if RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
0000
Reserved.
[3:0]
DOW
1–7
The current day-of-the-week.count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
Description
[7:4]
0000
Reserved.
[3:0]
DOW
01h–07h The current day-of-the-week count.
PS019215-0910
Real-Time Clock
eZ80F91 MCU
Product Specification
165
Real-Time Clock Day-of-the-Month Register
This register contains the current day-of-the-month count. The RTC_DOM register begins
counting at 01h. The value in the RTC_DOM register is unchanged by a RESET. The 
current setting of BCD_EN determines whether the values in this register are binary
(BCD_EN = 0) or binary-coded decimal (BCD_EN = 1). Access to this register is Read
Only if the RTC is locked, and Read/Write if the RTC is unlocked. See Table 84.
Table 84. Real-Time Clock Day-of-the-Month Register (RTC_DOM = 00E4h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TENS_DOM
0–3
The tens digit of the current day-of-the-month count.
[3:0]
DOM
0–9
The ones digit of the current day-of-the-month count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
DOM
01h–1Fh The current day-of-the-month count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
166
Real-Time Clock Month Register
This register contains the current month count. The RTC_MON register begins counting at
01h. The value in the RTC_MON register is unchanged by a RESET. The current setting
of BCD_EN determines whether the values in this register are binary (BCD_EN = 0) or
binary-coded decimal (BCD_EN = 1). Access to this register is Read Only if the RTC is
locked, and Read/Write if the RTC is unlocked. See Table 85.
Table 85. Real-Time Clock Month Register (RTC_MON = 00E5h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TENS_MON
0–1
The tens digit of the current month count.
[3:0]
MON
0–9
The ones digit of the current month count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
MON
01h–0Ch The current month count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
167
Real-Time Clock Year Register
This register contains the current year count. The value in the RTC_YR register is
unchanged by a RESET. The current setting of BCD_EN determines whether the values
in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
Access to this register is Read Only if the RTC is locked, and Read/Write if the RTC is
unlocked. See Table 86.
Table 86. Real-Time Clock Year Register (RTC_YR = 00E6h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TENS_YR
0–9
The tens digit of the current year count.
[3:0]
YR
0–9
The ones digit of the current year count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
YR
00h–63h The current year count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
168
Real-Time Clock Century Register
This register contains the current century count. The value in the RTC_CEN register is
unchanged by a RESET. The current setting of BCD_EN determines whether the values
in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
Access to this register is Read Only if the RTC is locked, and Read/Write if the RTC is
unlocked. See Table 87.
Table 87. Real-Time Clock Century Register (RTC_CEN = 00E7h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
R/W*
CPU Access
Note: X = Unchanged by RESET; R/W* = Read Only if RTC locked, Read/Write if RTC unlocked.
Binary-Coded-Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
TENS_CEN
0–9
The tens digit of the current century count.
[3:0]
CEN
0–9
The ones digit of the current century count.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
CEN
00h–63h The current century count.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
169
Real-Time Clock Alarm Seconds Register
This register contains the alarm seconds value. The value in the RTC_ASEC register is
unchanged by a RESET. The current setting of BCD_EN determines whether the values
in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1). See
Table 88.
Table 88. Real-Time Clock Alarm Seconds Register (RTC_ASEC = 00E8h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: X = Unchanged by RESET; R/W = Read/Write.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
ATEN_SEC
0–5
The tens digit of the alarm seconds value.
[3:0]
ASEC
0–9
The ones digit of the alarm seconds value.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
ASEC
00h–3Bh The alarm seconds value.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
170
Real-Time Clock Alarm Minutes Register
This register contains the alarm minutes value. The value in the RTC_AMIN register is
unchanged by a RESET. The current setting of BCD_EN determines whether the 
values in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
See Table 89.
Table 89. Real-Time Clock Alarm Minutes Register (RTC_AMIN = 00E9h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: X = Unchanged by RESET; R/W = Read/Write.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
ATEN_MIN
0–5
The tens digit of the alarm minutes value.
[3:0]
AMIN
0–9
The ones digit of the alarm minutes value.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
AMIN
00h–3Bh The alarm minutes value.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
171
Real-Time Clock Alarm Hours Register
This register contains the alarm hours value. The value in the RTC_AHRS register is
unchanged by a RESET. The current setting of BCD_EN determines whether the 
values in this register are binary (BCD_EN = 0) or binary-coded decimal (BCD_EN =
1). See Table 90.
Table 90. Real-Time Clock Alarm Hours Register (RTC_AHRS = 00EAh)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: X = Unchanged by RESET; R/W = Read/Write.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
ATEN_HRS
0–2
The tens digit of the alarm hours value.
[3:0]
AHRS
0–9
The ones digit of the alarm hours value.
Binary Operation (BCD_EN = 0)
Bit Position
Value
[7:0]
AHRS
00h–17h The alarm hours value.
PS019215-0910
Description
Real-Time Clock
eZ80F91 MCU
Product Specification
172
Real-Time Clock Alarm Day-of-the-Week Register
This register contains the alarm day-of-the-week value. The value in the RTC_ADOW
register is unchanged by a RESET. The current setting of BCD_EN determines whether
the value in this register is binary (BCD_EN = 0) or binary-coded decimal (BCD_EN = 1).
See Table 91.
Table 91. Real-Time Clock Alarm Day-of-the-Week Register (RTC_ADOW = 00EBh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
X
X
X
X
CPU Access
R
R
R
R
R/W*
R/W*
R/W*
R/W*
Note: X = Unchanged by RESET; R = Read Only; R/W* = Read Only if RTC locked, Read/Write if
RTC unlocked.
Binary-Coded Decimal Operation (BCD_EN = 1)
Bit Position
Value Description
[7:4]
0000
Reserved.
[3:0]
ADOW
1–7
The alarm day-of-the-week value.
Binary Operation (BCD_EN = 0)
Bit Position
Value
Description
[7:4]
0000
Reserved.
[3:0]
ADOW
01h–07h The alarm day-of-the-week value.
PS019215-0910
Real-Time Clock
eZ80F91 MCU
Product Specification
173
Real-Time Clock Alarm Control Register
This register contains control bits for the Real-Time Clock. The RTC_ACTRL register is
cleared by a RESET. See Table 92.
Table 92. Real-Time Clock Alarm Control Register (RTC_ACTRL = 00ECh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R/W
R/W
R/W
R/W
Note: X = Unchanged by RESET; R = Read Only; R/W = Read/Write
Bit Position
Value Description
[7:4]
0000
Reserved.
3
ADOW_EN
0
The day-of-the-week alarm is disabled.
1
The day-of-the-week alarm is enabled.
2
AHRS_EN
0
The hours alarm is disabled.
1
The hours alarm is enabled.
1
AMIN_EN
0
The minutes alarm is disabled.
1
The minutes alarm is enabled.
0
ASEC_EN
0
The seconds alarm is disabled.
1
The seconds alarm is enabled.
Real-Time Clock Control Register
This register contains control and status bits for the Real-Time Clock. Some bits in the
RTC_CTRL register are cleared by a RESET. The ALARM bit flag and associated interrupt (if INT_EN is enabled) are cleared by reading this register. The ALARM bit flag is
updated by clearing (locking) the RTC_UNLOCK bit or by an increment of the RTC
count. Writing to the RTC_CTRL register also resets the RTC count prescaler allowing the
RTC to be synchronized to another time source.
SLP_WAKE indicates if an RTC alarm condition initiated the CPU recovery from SLEEP
mode. This bit is checked after RESET to determine if a sleep-mode recovery is caused by
the RTC. SLP_WAKE is cleared by a Read of the RTC_CTRL register.
Setting the BCD_EN bit causes the RTC to use binary-coded decimal (BCD) counting in
all registers including the alarm set points.
The CLK_SEL and FREQ_SEL bits select the RTC clock source. If the 32 KHz crystal
option is selected, the oscillator is enabled and the internal prescaler is set to divide by
PS019215-0910
Real-Time Clock
eZ80F91 MCU
Product Specification
174
32768. If the power-line frequency option is selected, the prescale value is set by the
FREQ_SEL bit, and the 32 kHz oscillator is disabled. See Table 93.
Table 93. Real-Time Clock Control Register (RTC_CTRL = 00EDh)
Bit
7
6
5
4
3
2
1
0
Reset
X
0
X
X
X
X
0/1
0
CPU Access
R
R/W
R/W
R/W
R/W
R/W
R
R/W
Note: X = Unchanged by RESET; R = Read Only; R/W = Read/Write.
Bit Position
Value Description
7
ALARM
0
Alarm interrupt is inactive.
1
Alarm interrupt is active.
6
INT_EN
0
Interrupt on alarm condition is disabled.
1
Interrupt on alarm condition is enabled.
5
BCD_EN
0
RTC count and alarm value registers are binary.
1
RTC count and alarm value registers are BCD.
4
CLK_SEL
0
RTC clock source is crystal oscillator output (32768 Hz).
On-chip 32768Hz oscillator is enabled.
1
RTC clock source is power-line frequency input.
On-chip 32768 Hz oscillator is disabled.
3
FREQ_SEL
0
Power-line frequency is 60 Hz.
1
Power-line frequency is 50 Hz.
2
DAY_SAV
0
Suggested value for Daylight Savings Time not selected.
1
Suggested value for Daylight Savings Time selected. 
This register bit has been allocated as a storage location only
for software applications that use DST. No action is performed
in the eZ80F91 when setting or clearing this bit.
1
SLP_WAKE
0
RTC did not generate a sleep-mode recovery reset.
1
RTC Alarm generated a sleep-mode recovery reset.
0
RTC_UNLOCK
0
RTC count registers are locked to prevent write access.
RTC counter is enabled.
1
RTC count registers are unlocked to allow write access.
RTC counter is disabled.
PS019215-0910
Real-Time Clock
eZ80F91 MCU
Product Specification
175
Universal Asynchronous 
Receiver/Transmitter
¤
to eZ80 CPU
System Clock
I/O Address
Data
Interrupt Signal
UART Control Interface and Baud Rate Generator
The UART module implements all of the logic required to support the asynchronous communications protocol. The module also implements two separate 16-byte-deep FIFOs for
both transmission and reception. A block diagram of the UART is displayed in Figure 36.
Receive
Buffer
RxD0/RxD1
Transmit
Buffer
TxD0/TxD1
Modem
Control
Logic
CTS0/CTS1
RTS0/RTS1
DSR0/DSR1
DTR0/DTR1
DCD0/DCD1
RI0/RI1
Figure 36. UART Block Diagram
The UART module provides the following asynchronous communications protocolrelated features and functions:
•
•
•
•
•
•
PS019215-0910
5-, 6-, 7-, 8- or 9-bit data transmission.
Even/odd, space/mark, address/data, or no parity bit generation and detection.
Start and stop bit generation and detection (supports up to two stop bits).
Line break detection and generation.
Receiver overrun and framing errors detection.
Logic and associated I/O to provide modem handshake capability.
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
176
UART Functional Description
The UART Baud Rate Generator (BRG) creates the clock for the serial transmit and
receive functions. The UART module supports all of the various options in the asynchronous transmission and reception protocol including:
•
•
•
•
•
5- to 9-bit transmit/receive
Start bit generation and detection
Parity generation and detection
Stop bit generation and detection
Break generation and detection
The UART contains 16-byte-deep FIFOs in each direction. The FIFOs are enabled or disabled by the application. The receive FIFO features trigger-level detection logic, which
enables the CPU to block-transfer data bytes from the receive FIFO.
UART Functions
The UART function implements:
•
•
•
The transmitter and associated control logic
The receiver and associated control logic
The modem interface and associated logic
UART Transmitter
The transmitter block controls the data transmitted on the TxD output. It implements the
FIFO, access via the UARTx_THR register, the transmit shift register, the parity generator,
and control logic for the transmitter to control parameters for the asynchronous communications protocol.
The UARTx_THR is a Write Only register. The CPU writes the data byte to be transmitted
into this register. In FIFO mode, up to 16 data bytes are written via the UARTx_THR register. The data byte from the FIFO is transferred to the transmit shift register at the appropriate time and transmitted via TxD output. After SYNC_RESET, the UARTx_THR
register is empty. Therefore, the Transmit Holding Register Empty (THRE) bit (bit 5 of
the UARTx_LSR register) is 1. An interrupt is sent to the CPU if interrupts are enabled.
The CPU resets this interrupt by loading data into the UARTx_THR register, which clears
the transmitter interrupt.
The transmit shift register places the byte to be transmitted on the TxD signal serially. The
LSb of the byte to be transmitted is shifted out first and the MSb is shifted out last. The
control logic within the block adds the asynchronous communications protocol bits to the
data byte being transmitted. The transmitter block obtains the parameters for the protocol
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
177
from the bits programmed via the UARTx_LCTL register. When enabled, an interrupt is
generated after the final protocol bit is transmitted which the CPU resets by loading data
into the UARTx_THR register. The TxD output is set to 1 if the transmitter is idle (that is,
the transmitter does not contain any data to be transmitted).
The transmitter operates with the BRG clock. The data bits are placed on the TxD output
one time every 16 BRG clock cycles. The transmitter block also implements a parity generator that attaches the parity bit to the byte, if programmed. For 9-bit data, the host CPU
programs the parity bit generator so that it marks the byte as either address (mark parity)
or data (space parity).
UART Receiver
The receiver block controls the data reception from the RxD signal. The receiver block
implements a receiver shift register, receiver line error condition monitoring logic and
receiver data ready logic. It also implements the parity checker.
The UARTx_RBR is a Read Only register of the module. The CPU reads received data
from this register. The condition of the UARTx_RBR register is monitored by the DR bit
(bit 0 of the UARTx_LSR register). The DR bit is 1 when a data byte is received and transferred to the UARTx_RBR register from the receiver shift register. The DR bit is reset
only when the CPU reads all of the received data bytes. If the number of bits received is
less than eight, the unused MSb of the data byte Read are 0.
For 9-bit data, the receiver checks incoming bytes for space parity. A line status interrupt
is generated when an address byte is received, because address bytes maintain high parity
bits. The CPU clears the interrupt by determining if the address matches its own, then configures the receiver to either accept the subsequent data bytes if the address matches, or
ignore the data if the address does not match.
The receiver uses the clock from the BRG for receiving the data. This clock must operate
at 16 times the appropriate baud rate. The receiver synchronizes the shift clock on the falling edge of the RxD input start bit. It then receives a complete byte according to the set
parameters. The receiver also implements logic to detect framing errors, parity errors,
overrun errors, and break signals.
UART Modem Control
The modem control logic provides two outputs and four inputs for handshaking with the
modem. Any change in the modem status inputs, except RI, is detected and an interrupt is
generated. For RI, an interrupt is generated only when the trailing edge of the RI is
detected. The module also provides LOOP mode for self-diagnostics.
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
178
UART Interrupts
There are six different sources of interrupts from the UART. The six sources of interrupts
are:
•
•
•
Transmitter (two different interrupts)
Receiver (three different interrupts)
Modem status
UART Transmitter Interrupt
A Transmitter Hold Register Empty interrupt is generated if there is no data available in
the hold register. By the same token, a transmission complete interrupt is generated after
the data in the shift register is sent. Both interrupts are disabled using individual interrupt
enable bits, or cleared by writing data into the UARTx_THR register.
UART Receiver Interrupts
A receiver interrupt is generated by three possible events. The first event, a receiver data
ready interrupt event, indicates that one or more data bytes are received and are ready to
be read. Next, this interrupt is generated if the number of bytes in the receiver FIFO is
greater than or equal to the trigger level. If the FIFO is not enabled, the interrupt is generated if the receive buffer contains a data byte. This interrupt is cleared by reading the
UARTx_RBR.
The second interrupt source is the receiver time-out. A receiver time-out interrupt is generated when there are fewer data bytes in the receiver FIFO than the trigger level and there
are no Reads and Writes to or from the receiver FIFO for four consecutive byte times.
When the receiver time-out interrupt is generated, it is cleared only after emptying the
entire receive FIFO.
The first two interrupt sources from the receiver (data ready and time-out) share an interrupt enable bit. The third source of a receiver interrupt is a line status error, indicating an
error in byte reception. This error results from:
•
Note:
For 9-bit data, incorrect parity indicates detection of an address byte.
•
•
•
PS019215-0910
Incorrect received parity.
Incorrect framing (that is, the stop bit) is not detected by receiver at the end of the byte.
Receiver overrun condition.
A BREAK condition being detected on the receive data input.
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
179
An interrupt due to one of the above conditions is cleared when the UARTx_LSR register
is read. In case of FIFO mode, a line status interrupt is generated only after the received
byte with an error reaches the top of the FIFO and is ready to be read.
A line status interrupt is activated (provided this interrupt is enabled) as long as the Read
pointer of the receiver FIFO points to the location of the FIFO that contains a byte with the
error. The interrupt is immediately cleared when the UARTx_LSR register is read. The
ERR bit of the UARTx_LSR register is active as long as an erroneous byte is present in the
receiver FIFO.
UART Modem Status Interrupt
The modem status interrupt is generated if there is any change in state of the modem status
inputs to the UART. This interrupt is cleared when the CPU reads the UARTx_MSR register.
UART Recommended Usage
The following standard sequence of events occurs in the UART block of the eZ80F91
device. A description of each follows.
•
•
•
Module Reset
Control Transfers to Configure UART Operation
Data Transfers
Module Reset
Upon reset, all internal registers are set to their default values. All command status registers are programmed with their default values, and the FIFOs are flushed.
Control Transfers to Configure UART Operation
Based on the requirements of the application, the data transfer baud rate is determined and
the BRG is configured to generate a 16X clock frequency. Interrupts are disabled and the
communication control parameters are programmed in the UARTx_LCTL register. The
FIFO configuration is determined and the receive trigger levels are set in the
UARTx_FCTL register. The status registers, UARTx_LSR and UARTx_MSR, are read to
ensure that none of the interrupt sources are active. The interrupts are enabled (except for
the transmit interrupt) and the application is ready to use the module for transmission/
reception.
Data Transfers
Transmit—To transmit data, the application enables the transmit interrupt. An interrupt is
immediately expected in response. The application reads the UARTx_IIR register and
determines whether the interrupt occurs due to either an empty UARTx_THR register or a
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
180
completed transmission. When the application makes this determination, it writes the
transmit data bytes to the UARTx_THR register. The number of bytes that the application
writes depends on whether or not the FIFO is enabled. If the FIFO is enabled, the application writes 16 bytes at a time. If not, the application writes one byte at a time. As a result
of the first Write, the interrupt is deactivated. The CPU then waits for the next interrupt.
When the interrupt is raised by the UART module, the CPU repeats the same process until
it exhausts all of the data for transmission.
To control and check the modem status, the application sets up the modem by writing to
the UARTx_MCTL register and reading the UARTx_MCTL register before starting the
process described above.
In RS485 multidrop mode, the first byte of the message is the station address and the rest
of the message contains the data for that station. You must set the Even Parity Select (EPS
bit 4) and Parity Enable (PEN bit 3) in the UARTx_LCTL before sending the station
address. We recommend that in your UART initialization routine set up the
UARTx_LCTL register for your data transfer format and set the Parity Enable (PEN bit 3)
bit. Each time you want to send a new message you must perform these three steps:
1. Since the UART automatically clears the Even Parity Select (EPS bit 4) bit in the
UARTx_LCTL after a byte is sent, before starting a new message you have to wait for
the transmitter to go idle. The Transmit Empty (TEMT bit 6) of the UARTx_LSR will
be set. If you set the EPS bit of the UARTx_LCTL before the last byte of the previous
message is transmitted, the EPS bit will be cleared and the new station address will be
sent as data instead of being used as an address.
2. Set the Even Parity Select (EPS bit 4) bit in the UARTx_LCTL register being careful
not to alter the other bits in the register sets the address mark. Write station address to
the UARTx_THR. The UART will automatically clear the EPS bit after the station
address byte is transmitted.
3. Send the rest of the message. Write data to the UART Transmit Holding Register
UARTx_THR whenever the Transmit Holding Register Empty (THRE bit 5) in the
UARTx_LSR is set.
In multidrop mode, during receiving start address marks, you will see a receive line interrupt (INSTS bits[3:1]) in the IIR register. Read the LSR and check for receive errors only
and ignore any parity errors. The parity is only used for address marks in this multidrop
mode.
Receive—The receiver is always enabled, and it continually checks for the start bit on the
RxD input signal. When an interrupt is raised by the UART module, the application reads
the UARTx_IIR register and determines the cause for the interrupt. If the cause is a line
status interrupt, the application reads the UARTx_LSR register, reads the data byte and
then discards the byte or take other appropriate action. If the interrupt is caused by a
receive-data-ready condition, the application alternately reads the UARTx_LSR and
UARTx_RBR registers and removes all of the received data bytes. It reads the
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
181
UARTx_LSR register before reading the UARTx_RBR register to determine that there is
no error in the received data.
To control and check modem status, the application sets up the modem by writing to the
UARTx_MCTL register and reading the UARTx_MSR register before starting the process
described above.
Poll Mode Transfers—When interrupts are disabled, all data transfers are referred to as
poll mode transfers. In poll mode transfers, the application must continually poll the
UARTx_LSR register to transmit or receive data without enabling the interrupts. The
same holds true for the UARTx_MSR register. If the interrupts are not enabled, the data in
the UARTx_IIR register cannot be used to determine the cause of interrupt.
Baud Rate Generator
The Baud Rate Generator consists of a 16-bit downcounter, two registers, and associated
decoding logic. The initial value of the Baud Rate Generator is defined by the two BRG
Divisor Latch registers, {UARTx_BRG_H, UARTx_BRG_L}. At the rising edge of each
system clock, the BRG decrements until it reaches the value 0001h. On the next system
clock rising edge, the BRG reloads the initial value from {UARTx_BRG_H,
UARTx_BRG_L) and outputs a pulse to indicate the end-of-count.
Calculate the UART data rate with the following equation:
UART Data Rate (bits/s)
=
System Clock Frequency
16 X UART Baud Rate Generator Divisor
Upon RESET, the 16-bit BRG divisor value resets to the smallest allowable value of
0002h. Therefore, the minimum BRG clock divisor ratio is 2. A software Write to either
the Low- or High-byte registers for the BRG Divisor Latch causes both the Low and High
bytes to load into the BRG counter, and causes the count to restart.
The divisor registers are accessed only if bit 7 of the UART Line Control register
(UARTx_LCTL) is set to 1. After reset, this bit is reset to 0.
Recommended Use of the Baud Rate Generator
The following is the normal sequence of operations that must occur after the eZ80F91 is
powered on to configure the BRG:
1. Assert and deassert RESET.
2. Set UARTx_LCTL[7] to 1 to enable access of the BRG divisor registers.
3. Program the UARTx_BRG_L and UARTx_BRG_H registers.
4. Clear UARTx_LCTL[7] to 0 to disable access of the BRG divisor registers.
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
182
BRG Control Registers
UART Baud Rate Generator Register—Low and High Bytes
The registers hold the Low and High bytes of the 16-bit divisor count loaded by the CPU
for UART baud rate generation. The 16-bit clock divisor value is returned by
{UARTx_BRG_H, UARTx_BRG_L}, where x is either 0 or 1 to identify the two available
UART devices. Upon RESET, the 16-bit BRG divisor value resets to 0002h. The initial
16-bit divisor value must be between 0002h and FFFFh, because the values 0000h and
0001h are invalid and proper operation is not guaranteed at these two values. As a result,
the minimum BRG clock divisor ratio is 2.
A Write to either the Low- or High-byte registers for the BRG Divisor Latch causes both
bytes to be loaded into the BRG counter. The count is then restarted.
Bit 7 of the associated UART Line Control register (UARTx_LCTL) must be set to 1 to
access this register. See Table 94 and Table 95 on page 183. For more information, see
UART Line Control Register on page 188.
Note:
The UARTx_BRG_L registers share the same address space with the UARTx_RBR and
UARTx_THR registers. The UARTx_BRG_H registers share the same address space with
the UARTx_IER registers. Bit 7 of the associated UART Line Control register
(UARTx_LCTL) must be set to 1 to enable access to the BRG registers.
Table 94. UART Baud Rate Generator Register—Low Bytes (UART0_BRG_L = 00C0h,
UART1_BRG_L = 00D0h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
Bit 
Position
[7:0]
UART_BRG_L
PS019215-0910
Value
Description
00h–FFh
These bits represent the Low byte of the 16-bit BRG divider value. The
complete BRG divisor value is returned by {UART_BRG_H,
UART_BRG_L}.
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
183
Table 95. UART Baud Rate Generator Register—High Bytes (UART0_BRG_H = 00C1h,
UART1_BRG_H = 00D1h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
Bit 
Position
[7:0]
UART_BRG_H
Value
Description
00h–FFh
These bits represent the High byte of the 16-bit BRG divider value. The
complete BRG divisor value is returned by {UART_BRG_H,
UART_BRG_L}.
UART Registers
After a system reset, all UART registers are set to their default values. Any Writes to unused
registers or register bits are ignored and reads return a value of 0. For compatibility with
future revisions, unused bits within a register must always be written with a value of 0.
Read/Write attributes, reset conditions, and bit descriptions of all of the UART registers are
provided in this section.
UART Transmit Holding Register
If less than eight bits are programmed for transmission, the lower bits of the byte written
to this register are selected for transmission. The Transmit FIFO is mapped at this address.
You can write up to 16 bytes for transmission at one time to this address if the FIFO is
enabled by the application. If the FIFO is disabled, this buffer is only one byte deep.
These registers share the same address space as the UARTx_RBR and UARTx_BRG_L
registers. See Table 96 on page 184.
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
184
Table 96. UART Transmit Holding Registers (UART0_THR = 00C0h, UART1_THR = 00D0h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
[7:0]
TxD
Value
Description
00h–FFh Transmit data byte.
UART Receive Buffer Register
The bits in this register reflect the data received. If less than eight bits are programmed
for reception, the lower bits of the byte reflect the bits received, whereas upper unused
bits are 0. The Receive FIFO is mapped at this address. If the FIFO is disabled, this
buffer is only one byte deep.
These registers share the same address space as the UARTx_THR and UARTx_BRG_L
registers. See Table 97.
Table 97. UART Receive Buffer Registers (UART0_RBR = 00C0h, UART1_RBR = 00 D0h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit 
Position
[7:0]
RxD
Value
Description
00h–FFh
Receive data byte.
UART Interrupt Enable Register
The UARTx_IER register is used to enable and disable the UART interrupts. The
UARTx_IER registers share the same I/O addresses as the UARTx_BRG_H registers. See
Table 98 on page 185.
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
185
Table 98. UART Interrupt Enable Registers (UART0_IER = 00C1h, UART1_IER = 00D1h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
[7:5]
000
Reserved.
0
Transmission complete interrupt is disabled.
1
Transmission complete interrupt is generated when both the transmit hold
register and the transmit shift register are empty.
0
Modem interrupt on edge detect of status inputs is disabled.
1
Modem interrupt on edge detect of status inputs is enabled.
0
Line status interrupt is disabled.
1
Line status interrupt is enabled for receive data errors: incorrect parity bit
received, framing error, overrun error, or break detection.
0
Transmit interrupt is disabled.
1
Transmit interrupt is enabled. Interrupt is generated when the transmit
FIFO/buffer is empty indicating no more bytes available for transmission.
0
Receive interrupt is disabled.
1
Receive interrupt and receiver time-out interrupt are enabled. Interrupt is
generated if the FIFO/buffer contains data ready to be read or if the
receiver times out.
4
TCIE
3
MIIE
2
LSIE
1
TIE
0
RIE
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
186
UART Interrupt Identification Register
The Read Only UARTx_IIR register allows you to check whether the FIFO is enabled and
the status of interrupts. These registers share the same I/O addresses as the UARTx_FCTL
registers. See Table 99 and Table 100.
Table 99. UART Interrupt Identification Registers (UART0_IIR = 00C2h, UART1_IIR = 00D2h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
1
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit 
Position
Value
Description
[7]
FSTS
0
FIFO is disabled.
1
FIFO is enabled.
[6:4]
000
Reserved.
[3:1]
INSTS
000–
110
Interrupt Status Code.
The code indicated in these three bits is valid only if INTBIT is
1. If two internal interrupt sources are active and their
respective enable bits are High, only the higher priority
interrupt is seen by the application. The lower-priority interrupt
code is indicated only after the higher-priority interrupt is
serviced. Table 100 lists the interrupt status codes.
0
INTBIT
0
There is an active interrupt source within the UART.
1
There is not an active interrupt source within the UART.
Table 100. UART Interrupt Status Codes
PS019215-0910
INSTS
Value
Priority
Interrupt Type
011
Highest
Receiver Line Status
010
Second
Receive Data Ready or Trigger Level
110
Third
Character Time-out
101
Fourth
Transmission Complete
001
Fifth
Transmit Buffer Empty
000
Lowest
Modem Status
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
187
UART FIFO Control Register
This register is used to monitor trigger levels, clear FIFO pointers, and enable or disable
the FIFO. The UARTx_FCTL registers share the same I/O addresses as the UARTx_IIR
registers. See Table 101.
Table 101. UART FIFO Control Registers (UART0_FCTL = 00C2h, UART1_FCTL = 00D2h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
Value
Description
00
Receive FIFO trigger level set to 1. Receive data interrupt is
generated when there is 1 byte in the FIFO. Valid only if FIFO
is enabled.
01
Receive FIFO trigger level set to 4. Receive data interrupt is
generated when there are 4bytes in the FIFO. Valid only if
FIFO is enabled.
10
Receive FIFO trigger level set to 8. Receive data interrupt is
generated when there are 8 bytes in the FIFO. Valid only if
FIFO is enabled.
11
Receive FIFO trigger level set to 14. Receive data interrupt is
generated when there are 14 bytes in the FIFO. Valid only if
FIFO is enabled.
000b
Reserved—must be 000b.
0
Transmit Disable. This register bit works differently than the
standard 16550 UART. This bit must be set to transmit data.
When it is reset the transmit FIFO logic is reset along with the
associated transmit logic to keep them in sync. This bit is now
persistent–it does not self clear and it must remain at 1 to
transmit data.
1
Transmit Enable.
0
Receive Disable. This register bit works differently than the
standard 16550 UART. This bit must be set to receive data.
When it is reset the receive FIFO logic is reset along with the
associated receive logic to keep them in sync and avoid the
previous version’s lookup problem. This bit is now persistent–it
does not self clear and it must remain at 1 to receive data.
1
Receive Enable.
[7:6]
TRIG
[5:3]
2
CLRTxF
1
CLRRxF
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
188
Bit 
Position
0
FIFOEN
Value
Description
0
FIFOs are not used.
1
Receive and transmit FIFOs are used–You must clear the
FIFO logic using bits 1 and 2. First enable the FIFOs by setting
bit 0 to 1 then enable the receiver and transmitter by setting
bits 1 and 2.
UART Line Control Register
This register is used to control the communication control parameters. See Table 102 and
Table 103 on page 189.
Table 102. UART Line Control Registers (UART0_LCTL = 00C3h, UART1_LCTL = 00D3h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position Value
7
DLAB
6
SB
5
FPE
Description
0
Access to the UART registers at I/O addresses C0h, C1h, D0h and D1h is enabled.
1
Access to the Baud Rate Generator registers at I/O addresses C0h, C1h, D0h and
D1h is enabled.
0
Do not send a BREAK signal.
1
Send Break.
UART sends continuous zeroes on the transmit output from the next bit boundary.
The transmit data in the transmit shift register is ignored. After forcing this bit High,
the TxD output is 0 only after the bit boundary is reached. Just before forcing TxD to
0, the transmit FIFO is cleared. Any new data written to the transmit FIFO during a
break must be written only after the THRE bit of UARTx_LSR register goes High.
This new data is transmitted after the UART recovers from the break. After the break
is removed, the UART recovers from the break for the next BRG edge.
0
Do not force a parity error.
1
Force a parity error. When this bit and the parity enable bit (pen) are both 1, an
incorrect parity bit is transmitted with the data byte.
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
189
Bit 
Position Value
Description
0
Even Parity Select.
Use odd parity for transmit and receive. The total number of 1 bits in the transmit
data plus parity bit is odd. Used as SPACE bit in Multidrop Mode. See Table 104 on
page 189 for parity select definitions. Note: Receive Parity is set to SPACE in
multidrop mode.
1
Use even parity for transmit and receive. The total number of 1 bits in the transmit
data plus parity bit is even. Used as MARK bit in Multidrop Mode. See Table 104 on
page 189 for parity select definitions.
0
Parity bit transmit and receive is disabled.
1
Parity bit transmit and receive is enabled. For transmit, a parity bit is generated and
transmitted with every data character. For receive, the parity is checked for every
incoming data character. In Multidrop Mode, receive parity is checked for space
parity.
000–111
UART Character Parameter Selection.
See Table 103 on page 189 for a description of the values.
4
EPS
3
PEN
[2:0]
CHAR
Table 103. UART Character Parameter Definition
CHAR[2:0] Character Length (Tx/Rx Data Bits)
PS019215-0910
Stop Bits (Tx Stop Bits)
000
5
1
001
6
1
010
7
1
011
8
1
100
5
2
101
6
2
110
7
2
111
8
2
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
190
Table 104. Parity Select Definition for Multidrop Communications
Multidrop Mode
Even Parity Select
Parity Type
0
0
odd
0
1
even
1
0
space
1
1*
mark
Note: *In Multidrop Mode, EPS resets to 0 after the first character is sent.
UART Modem Control Register
This register is used to control and check the modem status. See Table 105.
Table 105. UART Modem Control Registers (UART0_MCTL = 00C4h, UART1_MCTL = 00D4h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value
Description
7
0
Reserved.
6
POLARITY
0
TxD and RxD signals—Normal Polarity.
1
Invert Polarity of TxD and RxD signals.
0
Multidrop Mode disabled.
1
Multidrop Mode enabled. See Table 104 on page 189 for parity select
definitions.
0
LOOP BACK mode is not enabled.
1
LOOP BACK mode is enabled.
The UART operates in internal LOOP BACK mode. The transmit data output
port is disconnected from the internal transmit data output and set to 1. The
receive data input port is disconnected and internal receive data is connected to
internal transmit data. The modem status input ports are disconnected and the
four bits of the modem control register are connected as modem status inputs.
The two modem control output ports (OUT1&2) are set to their inactive state.
5
MDM
4
LOOP
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
191
Bit 
Position
Value
Description
3
OUT2
0–1
No function in normal operation.
In LOOP BACK mode, this bit is connected to the DCD bit in the UART Status
Register.
2
OUT1
0–1
No function in normal operation.
In LOOP BACK mode, this bit is connected to the RI bit in the UART Status
Register.
1
RTS
0–1
Request to Send.
In normal operation, the RTS output port is the inverse of this bit. In LOOP
BACK mode, this bit is connected to the CTS bit in the UART Status Register.
0
DTR
0–1
Data Terminal Ready.
In normal operation, the DTR output port is the inverse of this bit. In LOOP
BACK mode, this bit is connected to the DSR bit in the UART Status Register.
UART Line Status Register
This register is used to show the status of UART interrupts and registers. See Table 106.
Table 106. UART Line Status Registers (UART0_LSR = 00C5h, UART1_LSR = 00 D5h)
Bit
7
6
5
4
3
2
1
0
Reset
0
1
1
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit 
Position
7
ERR
6
TEMT
PS019215-0910
Value
Description
0
Always 0 when operating in with the FIFO disabled. With the
FIFO enabled, this bit is reset when the UARTx_LSR register is
read and there are no more bytes with error status in the FIFO.
1
Error detected in the FIFO. There is at least 1 parity, framing or
break indication error in the FIFO.
0
Transmit holding register/FIFO is not empty or transmit shift
register is not empty or transmitter is not idle.
1
Transmit holding register/FIFO and transmit shift register are
empty; and the transmitter is idle. This bit cannot be set to 1
during the BREAK condition. This bit only becomes 1 after the
BREAK command is removed.
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
192
Bit 
Position
5
THRE
4
BI
3
FE
Value
Description
0
Transmit holding register/FIFO is not empty.
1
Transmit holding register/FIFO. This bit cannot be set to 1
during the BREAK condition. This bit only becomes 1 after the
BREAK command is removed.
0
Receiver does not detect a BREAK condition. This bit is reset
to 0 when the UARTx_LSR register is read.
1
Receiver detects a BREAK condition on the receive input line.
This bit is 1 if the duration of BREAK condition on the receive
data is longer than one character transmission time, the time
depends on the programming of the UARTx_LSR register. In
case of FIFO only one null character is loaded into the receiver
FIFO with the framing error. The framing error is revealed to
the eZ80® whenever that particular data is read from the
receiver FIFO.
0
No framing error detected for character at the top of the FIFO.
This bit is reset to 0 when the UARTx_LSR register is read.
1
Framing error detected for the character at the top of the FIFO.
This bit is set to 1 when the stop bit following the data/parity bit
is logic 0.
0
The received character at the top of the FIFO does not contain
a parity error. In multidrop mode, this indicates that the
received character is a data byte. This bit is reset to 0 when the
UARTx_LSR register is read.
1
The received character at the top of the FIFO contains a parity
error. In multidrop mode, this indicates that the received
character is an address byte.
0
The received character at the top of the FIFO does not contain
an overrun error. This bit is reset to 0 when the UARTx_LSR
register is read.
1
Overrun error is detected. If the FIFO is not enabled, this
indicates that the data in the receive buffer register was not
read before the next character was transferred into the receiver
buffer register. If the FIFO is enabled, this indicates the FIFO
was already full when an additional character was received by
the receiver shift register. The character in the receiver shift
register is not put into the receiver FIFO.
2
PE
1
OE
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
193
Bit 
Position
0
DR
Value
Description
0
This bit is reset to 0 when the UARTx_RBR register is read or
all bytes are read from the receiver FIFO.
1
Data ready. If the FIFO is not enabled, this bit is set to 1 when
a complete incoming character is transferred into the receiver
buffer register from the receiver shift register. If the FIFO is
enabled, this bit is set to 1 when a character is received and
transferred to the receiver FIFO.
UART Modem Status Register
This register is used to show the status of the UART signals. See Table 107.
Table 107. UART Modem Status Registers (UART0_MSR = 00C6h, UART1_MSR = 00 D6h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit 
Position
7
DCD
6
RI
5
DSR
4
CTS
PS019215-0910
Value
Description
0–1
Data Carrier Detect
In NORMAL mode, this bit reflects the inverted state of the
DCDx input pin. In LOOP BACK mode, this bit reflects the
value of the UARTx_MCTL[3] = out2.
0–1
Ring Indicator
In NORMAL mode, this bit reflects the inverted state of the RIx
input pin. In LOOP BACK mode, this bit reflects the value of the
UARTx_MCTL[2] = out1.
0–1
Data Set Ready
In NORMAL mode, this bit reflects the inverted state of the
DSRx input pin. In LOOP BACK mode, this bit reflects the
value of the UARTx_MCTL[0] = DTR.
0–1
Clear to Send
In NORMAL mode, this bit reflects the inverted state of the
CTSx input pin. In LOOP BACK mode, this bit reflects the value
of the UARTx_MCTL[1] = RTS.
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
194
Bit 
Position
Value
Description
0–1
Delta Status Change of DCD.
This bit is set to 1 whenever the DCDx pin changes state. This
bit is reset to 0 when the UARTx_MSR register is read.
2
TERI
0–1
Trailing Edge Change on RI.
This bit is set to 1 whenever a falling edge is detected on the
RIx pin. This bit is reset to 0 when the UARTx_MSR register is
read.
1
DDSR
0–1
Delta Status Change of DSR.
This bit is set to 1 whenever the DSRx pin changes state. This
bit is reset to 0 when the UARTx_MSR register is read.
0
DCTS
0–1
Delta Status Change of CTS.
This bit is set to 1 whenever the CTSx pin changes state.
This bit is reset to 0 when the UARTx_MSRs register is read.
3
DDCD
UART Scratch Pad Register
The UARTx_SPR register is used by the system as a general-purpose Read/Write register.
See Table 108.
Table 108. UART Scratch Pad Registers (UART0_SPR = 00C7h, UART1_SPR = 00D7h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
SPR
Value
Description
UART scratch pad register is available for use as a general00h–FFh purpose Read/Write register. In multi-drop 9 bit mode, this
register is used to store the address value.
PS019215-0910
Universal Asynchronous Receiver/Transmitter
eZ80F91 MCU
Product Specification
195
Infrared Encoder/Decoder
The eZ80F91 device contains a UART to an infrared encoder/decoder (endec). The endec
is integrated with the on-chip UART0 to allow easy communication between the CPU and
IrDA Physical Layer Specification Version 1.4-compatible infrared transceivers, as displayed in Figure 37. Infrared communication provides secure, reliable, high-speed, lowcost, point-to-point communication between PCs, PDAs, mobile telephones, printers, and
other infrared-enabled devices.
eZ80F91
Infrared
Transceiver
System
Clock
RxD
IR_RxD
TxD
IR_TxD
UART0
Baud Rate
Clock
Interrupt
I/O
Signal Address
Data
Infrared
Encoder/Decoder
RxD
TxD
I/O
Data
Address
¤
To eZ80 CPU
Figure 37. Infrared System Block Diagram
Functional Description
When the endec is enabled, the transmit data from the on-chip UART is encoded as digital
signals in accordance with the IrDA standard and output to the infrared transceiver. Likewise, data received from the infrared transceiver is decoded by the endec and passed to the
UART. Communication is half-duplex, meaning that simultaneous data transmission and
reception is not allowed.
The baud rate is set by the UART Baud Rate Generator (BRG), which supports IrDA standard baud rates from 9600 bps to 115.2 kbps. Higher baud rates are possible, but do not meet
PS019215-0910
Infrared Encoder/Decoder
eZ80F91 MCU
Product Specification
196
IrDA specifications. The UART must be enabled to use the endec. For more information on
the UART and its BRG, see Universal Asynchronous Receiver/Transmitter on page 175.
Transmit
The data to be transmitted via the IR transceiver is the data sent to UART0. The UART
transmit signal, TxD, and Baud Rate Clock are used by the endec to generate the
modulation signal, IR_TxD, that drives the infrared transceiver. Each UART bit is 16
clocks wide. If the data to be transmitted is a logical 1 (High), the IR_TxD signal remains
Low (0) for the full 16-clock period. If the data to be transmitted is a logical 0, a 3-clock
High (1) pulse is output following a 7-clock Low (0) period. Following the 3-clock High
pulse, a 6-clock Low pulse completes the full 16-clock data period. Data transmission is
displayed in Figure 38. During data transmission, the IR receive function must be disabled
by clearing the IR_RxEN bit in the IR_CTL reg to 0 to prevent transmitter-to-receiver
crosstalk.
16-clock
period
Baud Rate
Clock
UART_TxD
Start Bit = 0
Data Bit 0 = 1
Data Bit 1 = 0
Data Bit 2 = 1
Data Bit 3 = 1
3-clock
pulse
IR_TxD
7-clock
delay
Figure 38. Infrared Data Transmission
Receive
Data received from the IR transceiver via the IR_RxD signal is decoded by the endec and
passed to the UART. The IR_RxEN bit in the IR_CTL register must be set to enable the
receiver decoder. The IrDA serial infrared (SIR) data format uses half duplex communication. Therefore, the UART must not be allowed to transmit while the receiver decoder is
enabled. The UART Baud Rate Clock is used by the endec to generate the demodulated
signal, RxD, that drives the UART. Each UART bit is 16 clocks wide. If the data to be
received is a logical 1 (High), the IR_RxD signal remains High (1) for the full 16-clock
PS019215-0910
Infrared Encoder/Decoder
eZ80F91 MCU
Product Specification
197
period. If the data to be received is a logical 0, a delayed Low (0) pulse is output on RxD.
Data transmission is displayed in Figure 39.
16-clock
period
Baud Rate
Clock
Start Bit = 0
Data Bit 0 = 1
Data Bit 1 = 0
Data Bit 2 = 1
Data Bit 3 = 1
IR_RxD
UART_RxD
16-clock
period
8-clock
delay
16-clock
period
16-clock
period
16-clock
period
Figure 39. Infrared Data Reception
The IrDA endec is designed to ignore pulses on IR_RxD which do not comply with IrDA
pulse width specifications. Input pulses wider than five baud clocks (that is, 5/16 of a bit
period) are always ignored, as this would be a violation of the maximum pulse width specified for any standard baud rate up to 115.2 kbps. The check for minimum pulse widths is
optional, since using a slow system clock frequency limits the ability to accurately measure narrow pulse widths near the IrDA specification minimum of 1.41 us for the 
2.4–115.2 kbps rate range.
To enable checks of minimum input pulse width on IR_RxD, a non-zero value must be
programmed into the MIN_PULSE field of IR_CTL (bits [7:4]). This field forms the
most-significant four bits of the 6-bit down-counter used to determine if an input pulse
will be ignored because it is too narrow. The lower two counter bits are hard-coded to load
with 0x3, resulting in a total down-count equal to ((MIN_PULSE* 4) + 3). To be accepted,
input pulses must have a width greater than or equal to the down-count value times the
system clock period.
The following equation is used to determine an appropriate setting for MIN_PULSE:
MIN_PULSE = INT( ((Fsys*Wmin) - 3) / 4 )
Where,
Fsys is the frequency of the system clock, and,
Wmin is the minimum width of recognized input pulses.
PS019215-0910
Infrared Encoder/Decoder
eZ80F91 MCU
Product Specification
198
If this equation results in a value less than one, MIN_PULSE must be set to 0x0h which
enables edge detection and ensures that valid pulses wider than Wmin are accepted. The
field's maximum setting of 0xFh supports a Wmin of 1.25 us when Fsys is 50 MHz.
Jitter
Due to the inherent sampling of the received IR_RxD signal by the Bit Rate Clock, some
jitter is expected on the first bit in any sequence of data. However, all subsequent bits in
the received data stream are a fixed 16 clock periods wide.
Infrared Encoder/Decoder Signal Pins
The endec signal pins, IR_TxD and IR_RxD, are multiplexed with General-Purpose
Input/Output (GPIO) pins. These GPIO pins must be configured for alternate function
operation for the endec to operate.
The remaining six UART0 pins, CTS0, DCD0, DSR0, DTR0, RTS, and RI0, are not
required for use with the endec. The UART0 modem status interrupt must be disabled to
prevent unwanted interrupts from these pins. The GPIO pins corresponding to these six
unused UART0 pins are used for inputs, outputs, or interrupt sources. Recommended
GPIO Port D control register settings are listed in Table 109. See General-Purpose Input/
Output on page 49 for additional information on setting the GPIO Port modes.
Table 109. GPIO Mode Selection when using the IrDA Encoder/Decoder
GPIO Port D
Bits
Allowable GPIO
Port Mode
Allowable Port Mode Functions
PD0
7
Alternate Function
PD1
7
Alternate Function
PD2–PD7
Any other than GPIO Mode 7
(1, 2, 3, 4, 5, 6, 8, or 9)
Output, Input, Open-Drain, Open-Source, Levelsensitive Interrupt Input, or Edge-Triggered Interrupt
Input
Loopback Testing
Both internal and external loopback testing is accomplished with the endec on the eZ80F91
device. Internal loopback testing is enabled by setting the LOOP_BACK bit to 1. During
internal loopback, the IR_TxD output signal is inverted and connected on-chip to the
IR_RxD input. External loopback testing of the off-chip IrDA transceiver is accomplished
by transmitting data from the UART while the receiver is enabled (IR_RxEN set to 1).
PS019215-0910
Infrared Encoder/Decoder
eZ80F91 MCU
Product Specification
199
Infrared Encoder/Decoder Register
After a RESET, the Infrared Encoder/Decoder Register is set to its default value. Any
Writes to unused register bits are ignored and reads return a value of 0. The IR_CTL register is listed in Table 110.
Table 110. Infrared Encoder/Decoder Control Registers (IR_CTL = 00BFh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R
R/W
R/W
R/W
CPU Access
Note: R = Read only; R/W = Read/Write.
Bit 
Position
Value
Description
0000
Minimum receive pulse width control. When this field is equal to
0x0, the IrDA decoder uses edge detection to accept arbitrarily
narrow (that is, short) input pulses.
1h-Fh
When not equal to 0x0, this field forms the most-significant four
bits of the 6-bit down-counter used to determine if an input
pulse will be ignored because it is too narrow. The lower two
counter bits are hard-coded to load with 0x3, resulting in a total
down-count equal to ((IR_CTL[4:0]MIN_PULSE * 4) + 3). To be
accepted, input pulses must have a width greater than or equal
to the down-count value times the system clock period.
3
0
Reserved.
2
LOOP_BACK
0
Internal LOOP BACK mode is disabled.
1
Internal LOOP BACK mode is enabled.
IR_TxD output is inverted and connected to IR_RxD input for
internal loop back testing.
1
IR_RxEN
0
IR_RxD data is ignored.
1
IR_RxD data is passed to UART0 RxD.
0
IR_EN
0
Endec is disabled.
1
Endec is enabled.
[7:4]
MIN_PULSE
PS019215-0910
Infrared Encoder/Decoder
eZ80F91 MCU
Product Specification
200
PS019215-0910
Infrared Encoder/Decoder
eZ80F91 MCU
Product Specification
201
Serial Peripheral Interface
The Serial Peripheral Interface (SPI) is a synchronous interface allowing several SPI-type
devices to be interconnected. The SPI is a full-duplex, synchronous, character-oriented
communication channel that employs a four-wire interface. The SPI block consists of a
transmitter, receiver, baud rate generator, and control unit. During an SPI transfer, data is
sent and received simultaneously by both the master and the slave SPI devices.
In a serial peripheral interface, separate signals are required for data and clock. The SPI is
configured either as a master or as a slave. The connection of two SPI devices (one master
and one slave) and the direction of data transfer is displayed in Figure 40 and Figure 41.
MASTER
SS
DATAIN
MISO
Bit 7
Bit 0
8-Bit Shift Register
MOSI
DATAOUT
SCK
CLKOUT
Baud Rate
Generator
Figure 40. SPI Master Device
SLAVE
ENABLE
SS
DATAIN
MOSI
CLKIN
SCK
Bit 0
Bit 7
MISO
DATAOUT
8-Bit Shift Register
Figure 41. SPI Slave Device
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
202
SPI Signals
The four basic SPI signals are:
•
•
•
•
MISO (Master In, Slave Out)
MOSI (Master Out, Slave In)
SCK (SPI Serial Clock)
SS (Slave Select)
These SPI signals are discussed in the following paragraphs. Each signal is described in
both MASTER and SLAVE modes.
Master In, Slave Out
The Master In, Slave Out (MISO) pin is configured as an input in a master device and as
an output in a slave device. It is one of the two lines that transfer serial data, with the mostsignificant bit (msb) sent first. The MISO pin of a slave device is placed in a high-impedance state if the slave is not selected. When the SPI is not enabled, this signal is in a highimpedance state.
Master Out, Slave In
The Master Out, Slave In (MOSI) pin is configured as an output in a master device and as
an input in a slave device. It is one of the two lines that transfer serial data, with the msb
sent first. When the SPI is not enabled, this signal is in a high-impedance state.
Slave Select
The active Low Slave Select (SS) input signal is used to select the SPI as a slave device. It
must be Low prior to all data communication and must stay Low for the duration of the
data transfer.
The SS input signal must be High for the SPI to operate as a master device. If the SS signal
goes Low in Master mode, a Mode Fault error flag (MODF) is set in the SPI_SR register.
For more information, see SPI Status Register on page 209.
When the clock phase (CPHA) is set to 0, the shift clock is the logical OR of SS with
SCK. In this clock phase mode, SS must go High between successive characters in an
SPI message. When CPHA is set to 1, SS remains Low for several SPI characters. In
cases where there is only one SPI slave, its SS line could be tied Low as long as CPHA
is set to 1. For more information on CPHA, see SPI Control Register on page 208.
Serial Clock
The Serial Clock (SCK) is used to synchronize data movement both in and out of the
device via its MOSI and MISO pins. The master and slave are each capable of exchanging
a byte of data during a sequence of eight clock cycles. Because SCK is generated by the
master, the SCK pin becomes an input on a slave device. The SPI contains an internal
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
203
divide-by-two clock divider. In MASTER mode, the SPI serial clock is one-half the frequency of the clock signal created by the SPI’s Baud Rate Generator.
As displayed in Figure 42 and Table 111, four possible timing relations are chosen by
using the clock polarity (CPOL) and clock phase CPHA control bits in the SPI Control
register. See SPI Control Register on page 208. Both the master and slave must operate
with the identical timing, CPOL, and CPHA. The master device always places data on the
MOSI line a half-cycle before the clock edge (SCK signal), for the slave device to latch
the data.
Number of Cycles on the SCK Signal
1
2
3
4
5
6
7
8
SCK (CPOL bit = 0)
SCK (CPOL bit = 1)
Sample Input
(CPHA bit = 0) Data Out
MSB
Sample Input
(CPHA bit = 1) Data Out
MSB
6
5
6
4
5
3
4
2
3
1
2
LSB
1
LSB
ENABLE (To Slave)
Figure 42. SPI Timing
Table 111. SPI Clock Phase and Clock Polarity Operation
SS High
CPHA
CPOL
SCK
Transmit
Edge
0
0
Falling
Rising
Low
Yes
0
1
Rising
Falling
High
Yes
1
0
Rising
Falling
Low
No
1
1
Falling
Rising
High
No
PS019215-0910
SCK
Receive
Edge
SCK
Idle
State
Between
Characters?
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
204
SPI Functional Description
When a master transmits to a slave device via the MOSI signal, the slave device responds
by sending data to the master via the master's MISO signal. The result is a full-duplex
transmission, with both data out and data in synchronized with the same clock signal. The
byte transmitted is replaced by the byte received, eliminating the need for separate transmit-empty and receive-full status bits. A single status bit, SPIF, is used to signify that the
I/O operation is complete. See SPI Status Register on page 209.
The SPI is double-buffered during reads, but not during Writes. If a Write is performed
during data transfer, the transfer occurs uninterrupted, and the Write is unsuccessful. This
condition causes the write collision (WCOL) status bit in the SPI_SR register to be set.
After a data byte is shifted, the SPI flag of the SPI_SR register is set to 1.
In SPI MASTER mode, the SCK pin functions as an output. It idles High or Low depending on the CPOL bit in the SPI_CTL register until data is written to the shift register. Data
transfer is initiated by writing to the transmit shift register, SPI_TSR. Eight clocks are then
generated to shift the eight bits of transmit data out via the MOSI pin while shifting in
eight bits of data via the MISO pin. After transfer, the SCK signal becomes idle.
In SPI SLAVE mode, the start logic receives a logic Low from the SS pin and a clock
input at the SCK pin; as a result, the slave is synchronized to the master. Data from the
master is received serially from the slave MOSI signal and is loaded into the 8-bit shift
register. After the 8-bit shift register is loaded, its data is parallel-transferred to the Read
buffer. During a Write cycle, data is written into the shift register. Next, the slave waits for
the SPI master to initiate a data transfer, supply a clock signal, and shift the data out on the
slave's MISO signal.
If the CPHA bit in the SPI_CTL register is 0, a transfer begins when the SS pin signal goes
Low. The transfer ends when SS goes High after eight clock cycles on SCK. When the
CPHA bit is set to 1, a transfer begins the first time SCK becomes active while SS is Low.
The transfer ends when the SPI flag is set to 1.
SPI Flags
Mode Fault
The Mode Fault flag (MODF) indicates that there is a multimaster conflict in the system
control. The MODF bit is normally cleared to 0 and is only set to 1 when the master
device’s SS pin is pulled Low. When a mode fault is detected, the following sequence
occurs:
1. The MODF flag (SPI_SR[4]) is set to 1.
2. The SPI device is disabled by clearing the SPI_EN bit (SPI_CTL[5]) to 0.
3. The MASTER_EN bit (SPI_CTL[4]) is cleared to 0, forcing the device into SLAVE
mode.
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
205
4. If the SPI interrupt is enabled by setting IRQ_EN (SPI_CTL[7]) High, an SPI interrupt is generated.
Clearing the Mode Fault flag is performed by reading the SPI Status register. The other
SPI control bits (SPI_EN and MASTER_EN) must be restored to their original states by
user software after the Mode Fault Flag is cleared to 0.
Write Collision
The write collision flag, WCOL (SPI_SR[5]), is set to 1 when an attempt is made to write
to the SPI Transmit Shift register (SPI_TSR) while data transfer occurs. Clearing the
WCOL bit is performed by reading SPI_SR with the WCOL bit set to 1.
SPI Baud Rate Generator
The SPI’s Baud Rate Generator (BRG) creates a lower frequency clock from the high-frequency system clock. The BRG output is used as the clock source by the SPI.
Baud Rate Generator Functional Description
The SPI’s BRG consists of a 16-bit downcounter, two 8-bit registers, and associated
decoding logic. The BRG’s initial value is defined by the two BRG Divisor Latch registers
{SPI_BRG_H, SPI_BRG_L}. At the rising edge of each system clock, the BRG decrements until it reaches the value 0001h. On the next system clock rising edge, the BRG
reloads the initial value from {SPI_BRG_H, SPI_BRG_L) and outputs a pulse to indicate
the end of the count.
The SPI Data Rate is calculated using the following equation:
SPI Data Rate (bits/s)
=
System Clock Frequency
2 X SPI Baud Rate Generator Divisor
Upon RESET, the 16-bit BRG divisor value resets to 0002h. When the SPI is operating as
a Master, the BRG divisor value must be set to a value of 0003h or greater. When the SPI
is operating as a Slave, the BRG divisor value must be set to a value of 0004h or greater.
A software Write to either the Low- or High-byte registers for the BRG Divisor Latch
causes both the Low and High bytes to load into the BRG counter, and causes the count to
restart.
Data Transfer Procedure with SPI Configured as a Master
The following list describes the procedure for transferring data from a master SPI device
to a slave SPI device.
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
206
1. Load the SPI BRG Registers, SPI_BRG_H and SPI_BRG_L. The external device
must deassert the SS pin if currently asserted.
2. Load the SPI Control Register, SPI_CTL.
3. Assert the ENABLE pin of the slave device using a GPIO pin.
4. Load the SPI Transmit Shift Register, SPI_TSR.
5. When the SPI data transfer is complete, deassert the ENABLE pin of the slave device.
Data Transfer Procedure with SPI Configured as a Slave
The following list describes the procedure for transferring data from a slave SPI device to
a master SPI device.
1. Load the SPI BRG Registers, SPI_BRG_H and SPI_BRG_L.
2. Load the SPI Transmit Shift Register, SPI_TSR. This load cannot occur while the SPI
slave is currently receiving data.
3. Wait for the external SPI Master device to initiate the data transfer by asserting SS.
SPI Registers
There are six registers in the Serial Peripheral Interface that provide control, status, and
data storage functions. The SPI registers are described in the following paragraphs.
SPI Baud Rate Generator Registers—Low Byte and High Byte
These registers hold the Low and High bytes of the 16-bit divisor count loaded by the CPU
for baud rate generation. The 16-bit clock divisor value is returned by {SPI_BRG_H,
SPI_BRG_L}. Upon RESET, the 16-bit BRG divisor value resets to 0002h. When configured as a Master, the 16-bit divisor value must be between 0003h and FFFFh, inclusive.
When configured as a Slave, the 16-bit divisor value must be between 0004h and FFFFh,
inclusive.
A Write to either the Low- or High-byte registers for the BRG Divisor Latch causes both
bytes to be loaded into the BRG counter and a restart of the count. See Table 112 on page
207 and Table 113 on page 207.
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
207
Table 112. SPI Baud Rate Generator Register—Low Byte (SPI_BRG_L = 00B8h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
SPI_BRG_L
00h–
FFh
These bits represent the Low byte of the 16-bit BRG divider
value. The complete BRG divisor value is returned by
{SPI_BRG_H, SPI_BRG_L}.
Table 113. SPI Baud Rate Generator Register—High Byte (SPI_BRG_H = 00B9h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
[7:0]
00h–FFh
SPI_BRG_H
PS019215-0910
Description
These bits represent the High byte of the 16-bit BRG divider
value. The complete BRG divisor value is returned by
{SPI_BRG_H, SPI_BRG_L}.
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
208
SPI Control Register
This register is used to control and setup the serial peripheral interface. The SPI must be
disabled prior to making any changes to CPHA or CPOL. See Table 114.
Table 114. SPI Control Register (SPI_CTL = 00BAh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
1
0
0
R/W
R
R/W
R/W
R/W
R/W
R
R
CPU Access
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value Description
7
IRQ_EN
0
SPI system interrupt is disabled.
1
SPI system interrupt is enabled.
6
0
Reserved.
5
SPI_EN
0
SPI is disabled.
1
SPI is enabled.
4
MASTER_EN
0
When enabled, the SPI operates as a slave.
1
When enabled, the SPI operates as a master.
3
CPOL
0
Master SCK pin idles in a Low (0) state.
1
Master SCK pin idles in a High (1) state.
2
CPHA
0
SS must go High after transfer of every byte of data.
1
SS remains Low to transfer any number of data bytes.
[1:0]
00
Reserved.
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
209
SPI Status Register
The SPI Status Read Only register returns the status of data transmitted using the serial
peripheral interface. Reading the SPI_SR register clears Bits 7, 6, and 4 to a logical 0.
See Table 115.
Table 115. SPI Status Register (SPI_SR = 00BBh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
7
SPIF
6
WCOL
5
4
MODF
[3:0]
Value Description
0
SPI data transfer is not finished.
1
SPI data transfer is finished. If enabled, an interrupt is
generated. This bit flag is cleared to 0 by a Read of the
SPI_SR register.
0
An SPI write collision is not detected.
1
An SPI write collision is detected. This bit Flag is cleared to 0
by a Read of the SPI_SR registers.
0
Reserved.
0
A mode fault (multimaster conflict) is not detected.
1
A mode fault (multimaster conflict) is detected. This bit Flag is
cleared to 0 by a Read of the SPI_SR register.
0000
Reserved.
SPI Transmit Shift Register
The SPI Transmit Shift register (SPI_TSR) is used by the SPI master to transmit data over
SPI serial bus to the slave device. A Write to the SPI_TSR register places data directly into
the shift register for transmission. A Write to this register within an SPI device configured
as a master initiates transmission of the byte of the data loaded into the register. At the
completion of transmitting a byte of data, the SPI Flag (SPI_SR[7]) is set to 1 in both the
master and slave devices.
The SPI Transmit Shift Write Only register shares the same address space as the SPI
Receive Buffer Read Only register. See Table 116 on page 210.
PS019215-0910
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
210
Table 116. SPI Transmit Shift Register (SPI_TSR = 00BCh)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
[7:0]
TX_DATA
Value
Description
00h–FFh SPI transmit data.
SPI Receive Buffer Register
The SPI Receive Buffer register (SPI_RBR) is used by the SPI slave to receive data from
the serial bus. The SPIF bit must be cleared prior to a second transfer of data from the shift
register; otherwise, an overrun condition exists. In the event of an overrun, the byte that
causes the overrun is lost.
The SPI Receive Buffer Read Only register shares the same address space as the SPI
Transmit Shift Write Only register. See Table 117.
Table 117. SPI Receive Buffer Register (SPI_RBR = 00BCh)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
RX_DATA
PS019215-0910
Value
Description
00h–FFh
SPI received data.
Serial Peripheral Interface
eZ80F91 MCU
Product Specification
211
I2C Serial I/O Interface
I2C General Characteristics
The Inter-Integrated Circuit (I2C) serial I/O bus is a two-wire communication interface
that operates in four modes:
•
•
•
•
MASTER TRANSMIT
MASTER RECEIVE
SLAVE TRANSMIT
SLAVE RECEIVE
The I2C interface consists of a Serial Clock (SCL) and Serial Data (SDA). Both SCL and
SDA are bidirectional lines connected to a positive supply voltage via an external pull-up
resistor. When the bus is free, both lines are High. The output stages of devices connected
to the bus must be configured as open-drain outputs. Data on the I2C bus are transferred at
a rate of up to 100 kbps in STANDARD mode, or up to 400 kbps in FAST mode. One
clock pulse is generated for each data bit transferred.
Clocking Overview
If another device on the I2C bus drives the clock line when the I2C is in MASTER mode,
the I2C synchronizes its clock to the I2C bus clock. The High period of the clock is
determined by the device that generates the shortest High clock period. The Low period of
the clock is determined by the device that generates the longest Low clock period.
The Low period of the clock is stretched by a slave to slow down the bus master. The Low
period is also stretched for handshaking purposes. This result is accomplished after each
bit transfer or each byte transfer. The I2C stretches the clock after each byte transfer until
the IFLG bit in the I2C_CTL register is cleared to 0.
Bus Arbitration Overview
In MASTER mode, the I2C checks that each transmitted logic 1 appears on the I2C bus as
a logic 1. If another device on the bus overrules and pulls the SDA signal Low, arbitration
is lost. If arbitration is lost during the transmission of a data byte or a Not Acknowledge
(NACK) bit, the I2C returns to an idle state. If arbitration is lost during the transmission of
an address, the I2C switches to SLAVE mode so that it recognizes its own slave address or
the general call address.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
212
Data Validity
The data on the SDA line must be stable during the High period of the clock. The High or
Low state of the data line changes only when the clock signal on the SCL line is Low, as
displayed in Figure 43.
SDA Signal
SCL Signal
Data Line
Stable
Data Valid
Change of
Data Allowed
Figure 43. I2C Clock and Data Relationship
START and STOP Conditions
Within the I2C bus protocol, unique situations arise which are defined as START and
STOP conditions. Figure 44 displays a High-to-Low transition on the SDA line while SCL
is High, indicating a START condition. A Low-to-High transition on the SDA line while
SCL is High defines a STOP condition.
START and STOP conditions are always generated by the master. The bus is considered to
be busy after a START condition. The bus is considered to be free for a defined time after
a STOP condition.
SDA Signal
SCL Signal
S
P
START Condition
STOP Condition
Figure 44. START and STOP Conditions In I2C Protocol
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
213
Transferring Data
Byte Format
Every character transferred on the SDA line must be a single 8-bit byte. The number of
bytes that is transmitted per transfer is unrestricted. Each byte must be followed by an
Acknowledge (ACK). Data is transferred with the most-significant bit (msb) first.
Figure 45 displays a receiver that holds the SCL line Low to force the transmitter into a
Wait state. Data transfer then continues when the receiver is ready for another byte of data
and releases SCL.
SDA Signal
MSB
SCL Signal
1
Acknowledge from
Receiver
2
8
9
Acknowledge from
Receiver
1
S
START Condition
9
ACK
P
STOP Condition
Clock Line Held Low By Receiver
2
Figure 45. I C Frame Structure
Acknowledge
Data transfer with an ACK function is obligatory. The ACK-related clock pulse is generated by the master. The transmitter releases the SDA line (High) during the ACK
clock pulse. The receiver must pull down the SDA line during the ACK clock pulse so
that it remains stable (Low) during the High period of this clock pulse. See Figure 46
on page 214.
A receiver that is addressed is obliged to generate an ACK after each byte is received.
When a slave receiver does not acknowledge the slave address (for example, unable to
receive because it is performing some real-time function), the data line must be left High
by the slave. The master then generates a STOP condition to abort the transfer.
If a slave receiver acknowledges the slave address, but cannot receive any more data
bytes, the master must abort the transfer. The abort is indicated by the slave generating the
Not Acknowledge (NACK) on the first byte to follow. The slave leaves the data line High
and the master generates the STOP condition.
If a master receiver is involved in a transfer, it must signal the end of the data stream to the
slave transmitter by not generating an ACK on the final byte that is clocked out of the
slave. The slave transmitter must release the data line to allow the master to generate a
STOP or a repeated START condition.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
214
Data Output
by Transmitter
MSB
Data Output
by Receiver
1
S
SCL Signal
from Master
1
2
8
9
START Condition
Clock Pulse for Acknowledge
Figure 46. I2C Acknowledge
Clock Synchronization
All masters generate their own clocks on the SCL line to transfer messages on the I2C bus.
Data is only valid during the High period of each clock.
Clock synchronization is performed using the wired AND connection of the I2C interfaces
to the SCL line, meaning that a High-to-Low transition on the SCL line causes the relevant
devices to start counting from their Low period. When a device clock goes Low, it holds
the SCL line in that state until the clock High state is reached. See Figure 47 on page 215.
The Low-to-High transition of this clock, however, cannot change the state of the SCL
line if another clock is still within its Low period. The SCL line is held Low by the device
with the longest Low period. Devices with shorter Low periods enter a High wait state
during this time.
When all devices count off the Low period, the clock line is released and goes High. There
is no difference between the device clocks and the state of the SCL line; all of the devices
start counting the High periods. The first device to complete its High period again pulls
the SCL line Low. In this way, a synchronized SCL clock is generated with its Low period
determined by the device with the longest clock Low period, and its High period
determined by the device with the shortest clock High period.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
215
Wait
State
Start Counting
High Period
CLK1 Signal
Counter
Reset
CLK2 Signal
SCL Signal
Figure 47. Clock Synchronization In I2C Protocol
Arbitration
Any master initiates a transfer if the bus is free. As a result, multiple masters each generates a START condition if the bus is free within a minimum period. If multiple masters
generate a START condition, a START is defined for the bus. However, arbitration defines
which MASTER controls the bus. Arbitration takes place on the SDA line. As mentioned,
START conditions are initiated only while the SCL line is held High. If during this period,
a master (M1) initiates a High-to-Low transition—that is, a START condition—while a
second master (M2) transmits a Low signal on the line, then the first master, M1, cannot
take control of the bus. As a result, the data output stage for M1 is disabled.
Arbitration continues for many bits. Its first stage is comparison of the address bits. If the
masters are each trying to address the same device, arbitration continues with a comparison of the data. Because address and data information on the I2C bus is used for arbitration, no information is lost during this process. A master that loses the arbitration
generates clock pulses until the end of the byte in which it loses the arbitration.
If a master also incorporates a slave function and it loses arbitration during the addressing
stage, it is possible that the winning master is trying to address it. The losing master must
switch over immediately to its slave receiver mode. Figure 47 displays the arbitration procedure for two masters. Of course, more masters can be involved, depending on how many
masters are connected to the bus. The moment there is a difference between the internal
data level of the master generating DATA 1 and the actual level on the SDA line, its data
output is switched off, which means that a High output level is then connected to the bus.
As a result, the data transfer initiated by the winning master is not affected. Because control of the I2C bus is decided solely on the address and data sent by competing masters,
there is no central master, nor any order of priority on the bus.
Special attention must be paid if, during a serial transfer, the arbitration procedure is still
in progress at the moment when a repeated START condition or a STOP condition is transmitted to the I2C bus. If it is possible for such a situation to occur, the masters involved
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
216
must send this repeated START condition or STOP condition at the same position in the
format frame. In other words, arbitration is not allowed between:
•
•
•
A repeated START condition and a data bit.
A STOP condition and a data bit.
A repeated START condition and a STOP condition.
Clock Synchronization for Handshake
The clock-synchronizing mechanism functions as a handshake, enabling receivers to cope
with fast data transfers, on either a byte or a bit level. The byte level allows a device to
receive a byte of data at a fast rate, but allows the device more time to store the received
byte or to prepare another byte for transmission. Slaves hold the SCL line Low after reception and acknowledge the byte, forcing the master into a Wait state until the slave is ready
for the next byte transfer in a handshake procedure.
Operating Modes
Master Transmit
In MASTER TRANSMIT mode, the I2C transmits a number of bytes to a slave receiver.
Enter MASTER TRANSMIT mode by setting the STA bit in the I2C_CTL register to 1.
The I2C then tests the I2C bus and transmits a START condition when the bus is free.
When a START condition is transmitted, the IFLG bit is 1 and the status code in the
I2C_SR register is 08h. Before this interrupt is serviced, the I2C_DR register must be
loaded with either a 7-bit slave address or the first part of a 10-bit slave address, with the
lsb cleared to 0 to specify TRANSMIT mode. The IFLG bit must now be cleared to 0 to
prompt the transfer to continue.
After the 7-bit slave address (or the first part of a 10-bit address) plus the Write bit are
transmitted, the IFLG is set again. A number of status codes are possible in the I2C_SR
register. See Table 118 on page 217.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
217
Table 118. I2C Master Transmit Status Codes
Code
I2C State
Microcontroller Response
Next I2C Action
18h
Addr+W transmitted
ACK received1
For a 7-bit address: write byte to DATA,
clear IFLG
Transmit data byte,
receive ACK
Or set STA, clear IFLG
Transmit repeated
START
Or set STP, clear IFLG
Transmit STOP
Or set STA & STP, clear IFLG
Transmit STOP then
START
For a 10-bit address: write extended
address byte to data, clear IFLG
Transmit extended
address byte
20h
Addr+W transmitted,
ACK not received
Same as code 18h
Same as code 18h
38h
Arbitration lost
Clear IFLG
Return to idle
Or set STA, clear IFLG
Transmit START when
bus is free
Arbitration lost, 
+W received, 
ACK transmitted
Clear IFLG, AAK = 02
Receive data byte,
transmit NACK
Or clear IFLG, AAK = 1
Receive data byte,
transmit ACK
78h
Arbitration lost,
General call address
received, ACK
transmitted
Same as code 68h
Same as code 68h
B0h
Arbitration lost, 
SLA+R received, 
ACK transmitted3
Write byte to DATA, clear IFLG, clear AAK Transmit last byte,
=0
receive ACK
68h
Or write byte to DATA, clear IFLG, set AAK Transmit data byte,
=1
receive ACK
Notes
1. W is defined as the Write bit; that is, the lsb is cleared to 0.
2. AAK is an I2C control bit that identifies which ACK signal to transmit.
3. R is defined as the Read bit; that is, the lsb is set to 1.
If 10-bit addressing is used, the status code is 18h or 20h after the first part of a 10-bit
address, plus the Write bit, are successfully transmitted.
After this interrupt is serviced and the second part of the 10-bit address is transmitted, the
I2C_SR register contains one of the codes listed in Table 119.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
218
Table 119. I2C 10-Bit Master Transmit Status Codes
Code
I2C State
Microcontroller Response
Next I2C Action
38h
Arbitration lost
Clear IFLG
Return to idle
Or set STA, clear IFLG
Transmit START when bus free
Arbitration lost,
SLA+W received,
ACK transmitted1
Clear IFLG, clear AAK = 02
Receive data byte, transmit NACK
Or clear IFLG, set AAK = 1
Receive data byte, transmit ACK
Arbitration lost,
SLA+R received,
ACK transmitted3
Write byte to DATA,
clear IFLG, clear AAK = 0
Transmit last byte,
receive ACK
Or write byte to DATA,
clear IFLG, set AAK = 1
Transmit data byte,
receive ACK
Second address byte
+ W transmitted,
ACK received
Write byte to data,
clear IFLG
Transmit data byte,
receive ACK
Or set STA, clear IFLG
Transmit repeated START
Or set STP, clear IFLG
Transmit STOP
Or set STA & STP,
clear IFLG
Transmit STOP then
START
Same as code D0h
Same as code D0h
68h
B0h
D0h
D8h
Second address byte
+ W transmitted,
ACK not received
Notes
1. W is defined as the Write bit; that is, the lsb is cleared to 0.
2. AAK is an I2C control bit that identifies which ACK signal to transmit.
3. R is defined as the Read bit; that is, the lsb is set to 1.
If a repeated START condition is transmitted, the status code is 10h instead of 08h. After
each data byte is transmitted, the IFLG is set to 1 and one of the status codes listed in
Table 120 is loaded into the I2C_SR register.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
219
Table 120. I2C Master Transmit Status Codes For Data Bytes
Code
I2C State
Microcontroller Response
Next I2C Action
28h
Data byte transmitted,
ACK received
Write byte to data,
clear IFLG
Transmit data byte,
receive ACK
Or set STA, clear IFLG
Transmit repeated START
Or set STP, clear IFLG
Transmit STOP
Or set STA & STP,
clear IFLG
Transmit START then STOP
30h
Data byte transmitted, Same as code 28h
ACK not received
Same as code 28h
38h
Arbitration lost
Clear IFLG
Return to idle
Or set STA, clear IFLG
Transmit START when bus free
When all bytes are transmitted, the microcontroller must write a 1 to the STP bit in the
I2C_CTL register. The I2C then transmits a STOP condition, clears the STP bit and returns
to an idle state.
Master Receive
In MASTER RECEIVE mode, the I2C receives a number of bytes from a slave
transmitter.
After the START condition is transmitted, the IFLG bit is 1 and the status code 08h is
loaded into the I2C_SR register. The I2C_DR register must be loaded with the slave
address (or the first part of a 10-bit slave address), with the lsb set to 1 to signify a Read.
The IFLG bit must be cleared to 0 as a prompt for the transfer to continue.
When the 7-bit slave address (or the first part of a 10-bit address) and the Read bit are
transmitted, the IFLG bit is set and one of the status codes listed in Table 121 on page 220
is loaded into the I2C_SR register.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
220
Table 121. I2C Master Receive Status Codes
Code I2C State
Microcontroller Response
Next I2C Action
40h
For a 7-bit address,
clear IFLG, AAK = 01
Receive data byte,
transmit NACK
Or clear IFLG, AAK = 1
Receive data byte,
transmit ACK
For a 10-bit address
Write extended address
byte to data, clear IFLG
Transmit extended address byte
For a 7-bit address:
Set STA, clear IFLG
Transmit repeated START
Or set STP, clear IFLG
Transmit STOP
Or set STA & STP,
clear IFLG
Transmit STOP then START
48h
Addr + R transmitted,
ACK received
Addr + R transmitted,
ACK not received2
For a 10-bit address:
Transmit extended address byte
Write extended address byte to data,
clear IFLG
38h
Clear IFLG
Return to idle
Or set STA, clear IFLG
Transmit START when bus is free
Arbitration lost,
SLA+W received,
ACK transmitted3
Clear IFLG, clear AAK = 0
Receive data byte,
transmit NACK
Or clear IFLG, set AAK = 1
Receive data byte,
transmit ACK
78h
Arbitration lost,
General call addr
received, ACK
transmitted
Same as code 68h
Same as code 68h
B0h
Arbitration lost,
SLA+R received,
ACK transmitted
Write byte to DATA,
clear IFLG, clear AAK = 0
Transmit last byte,
receive ACK
Or write byte to DATA,
clear IFLG, set AAK = 1
Transmit data byte,
receive ACK
68h
Arbitration lost
Notes
1. AAK is an I2C control bit that identifies which ACK signal to transmit.
2. R is defined as the Read bit; that is, the lsb is set to 1.
3. W is defined as the Write bit; that is, the lsb is cleared to 0.
If 10-bit addressing is being used, the slave is first addressed using the full 10-bit address,
plus the Write bit. The master then issues a restart followed by the first part of the 10-bit
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
221
address again, this time with the Read bit. The status code then becomes 40h or 48h. It is
the responsibility of the slave to remember that it had been selected prior to the restart.
If a repeated START condition is received, the status code is 10h instead of 08h.
After each data byte is received, the IFLG is set to 1 and one of the status codes listed in
Table 122 is loaded into the I2C_SR register.
Table 122. I2C Master Receive Status Codes For Data Bytes
Code
I2C State
Microcontroller Response
Next I2C Action
50h
Data byte received,
ACK transmitted
Read data, clear IFLG,
clear AAK = 0*
Receive data byte,
transmit NACK
Or read data, clear IFLG,
set AAK = 1
Receive data byte,
transmit ACK
Read data, set STA,
clear IFLG
Transmit repeated
START
Or read data, set STP,
clear IFLG
Transmit STOP
Or read data, set
STA & STP, clear IFLG
Transmit STOP then
START
Same as master transmit
Same as master
transmit
58h
38h
Data byte received,
NACK transmitted
Arbitration lost in
NACK bit
Note: AAK is an I2C control bit that identifies which ACK signal to transmit.
When all bytes are received, a NACK must be sent, then the microcontroller must write 1
to the STP bit in the I2C_CTL register. The I2C then transmits a STOP condition, clears
the STP bit and returns to an idle state.
Slave Transmit
In SLAVE TRANSMIT mode, a number of bytes are transmitted to a master receiver.
The I2C enters SLAVE TRANSMIT mode when it receives its own slave address and a
Read bit after a START condition. The I2C then transmits an ACK bit (if the AAK bit is
set to 1); it then sets the IFLG bit in the I2C_CTL register. As a result, the I2C_SR register
contains the status code A8h.
Note:
PS019215-0910
When I2C contains a 10-bit slave address (signified by the address range F0h–F7h in the
I2C_SAR register), it transmits an ACK when the first address byte is received after a
restart. An interrupt is generated and IFLG is set to 1; however, the status does not
change. No second address byte is sent by the master. It is up to the slave to remember it
had been selected prior to the restart.
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
222
I2C goes from MASTER mode to SLAVE TRANSMIT mode when arbitration is lost during the transmission of an address, and the slave address and Read bit are received. This
action is represented by the status code B0h in the I2C_SR register.
The data byte to be transmitted is loaded into the I2C_DR register and the IFLG bit is
cleared to 0. After the I2C transmits the byte and receives an ACK, the IFLG bit is set to 1
and the I2C_SR register contains B8h. When the final byte to be transmitted is loaded into
the I2C_DR register, the AAK bit is cleared when the IFLG is cleared to 0. After the final
byte is transmitted, the IFLG is set and the I2C_SR register contains C8h and the I2C
returns to an idle state. The AAK bit must be set to 1 before reentering SLAVE mode.
If no ACK is received after transmitting a byte, the IFLG is set and the I2C_SR register
contains C0h. The I2C then returns to an idle state. If a STOP condition is detected after an
ACK bit, the I2C returns to an idle state.
Slave Receive
In SLAVE RECEIVE mode, a number of data bytes are received from a master transmitter. The I2C enters SLAVE RECEIVE mode when it receives its own slave address and a
Write bit (lsb = 0) after a START condition. The I2C transmits an ACK bit and sets the
IFLG bit in the I2C_CTL register and the I2C_SR register contains the status code 60h.
The I2C also enters SLAVE RECEIVE mode when it receives the general call address 00h
(if the GCE bit in the I2C_SAR register is set). The status code is then 70h.
Note:
When the I2C contains a 10-bit slave address (signified by F0h–F7h in the I2C_SAR register), it transmits an acknowledge after the first address byte is received but no interrupt is
generated. IFLG is not set and the status does not change. The I2C generates an interrupt
only after the second address byte is received. The I2C sets the IFLG bit and loads the status code as described above.
I2C goes from MASTER mode to SLAVE RECEIVE mode when arbitration is lost during
the transmission of an address, and the slave address and Write bit (or the general call
address if the CGE bit in the I2C_SAR register is set to 1) are received. The status code in
the I2C_SR register is 68h if the slave address is received or 78h if the general call
address is received. The IFLG bit must be cleared to 0 to allow data transfer to continue.
If the AAK bit in the I2C_CTL register is set to 1 then an ACK bit (Low level on SDA) is
transmitted and the IFLG bit is set after each byte is received. The I2C_SR register contains the two status codes 80h or 90h if SLAVE RECEIVE mode is entered with the general call address. The received data byte are read from the I2C_DR register and the IFLG
bit must be cleared to allow the transfer to continue. If a STOP condition or a repeated
START condition is detected after the acknowledge bit, the IFLG bit is set and the I2C_SR
register contains status code A0h.
If the AAK bit is cleared to 0 during a transfer, the I2C transmits a NACK bit (High level
on SDA) after the next byte is received, and sets the IFLG bit to 1. The I2C_SR register
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
223
contains the two status codes 88h or 98h if SLAVE RECEIVE mode is entered with the
general call address. The I2C returns to an idle state when the IFLG bit is cleared to 0.
I2C Registers
The section that follows describes each of the eZ80F91 MCU’s Inter-Integrated Circuit
(I2C) registers.
Addressing
The CPU interface provides access to seven 8-bit registers: four Read/Write registers, one
Read Only register and two Write Only registers, as listed in Table 123.
Table 123. I2C Register Descriptions
Register
Description
I2C_SAR
Slave address register
I2C_XSAR
Extended slave address register
I2C_DR
Data byte register
I2C_CTL
Control register
I2C_SR
Status register (Read Only)
I2C_CCR
Clock Control register (Write Only)
I2C_SRR
Software reset register (Write Only)
Resetting the I2C Registers
Hardware Reset—When the I2C is reset by a hardware reset of the eZ80F91 device, the
I2C_SAR, I2C_XSAR, I2C_DR, and I2C_CTL registers are cleared to 00h; while the
I2C_SR register is set to F8h.
Software Reset—Perform a software reset by writing any value to the I2C Software Reset
Register (I2C_SRR). A software reset clears the STP, STA, and IFLG bits of the I2C_CTL
register to 0 and sets the I2C back to an idle state.
I2C Slave Address Register
The I2C_SAR register provides the 7-bit address of the I2C when in SLAVE mode and
allows 10-bit addressing in conjunction with the I2C_XSAR register. I2C_SAR[7:1] =
SLA[6:0] is the 7-bit address of the I2C when in 7-bit SLAVE mode. When the I2C
receives this address after a START condition, it enters SLAVE mode. I2C_SAR[7] corresponds to the first bit received from the I2C bus.
When the register receives an address starting with F7h to F0h (I2C_SAR[7:3] = 11110b),
the I2C recognizes that a 10-bit slave addressing mode is being selected. The I2C sends an
ACK after receiving the I2C_SAR byte (the device does not generate an interrupt at this
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
224
point). After the next byte of the address (I2C_XSAR) is received, the I2C generates an
interrupt and enters SLAVE mode.Then I2C_SAR[2:1] are used as the upper 2 bits for the
10-bit extended address. The full 10-bit address is supplied by {I2C_SAR[2:1],
I2C_XSAR[7:0]}. See Table 124.
Table 124. I2C Slave Address Register (I2C_SAR = 00C8h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
[7:1]
SLA
00h–7Fh 7-bit slave address or upper 2 bits, I2C_SAR[2:1], of
address when operating in 10-bit mode.
0
GCE
0
I2C not enabled to recognize the General Call Address.
1
I2C enabled to recognize the General Call Address.
Description
I2C Extended Slave Address Register
The I2C_XSAR register is used in conjunction with the I2C_SAR register to provide 10bit addressing of the I2C when in SLAVE mode. The I2C_SAR value forms the lower 8
bits of the 10-bit slave address. The full 10-bit address is supplied by {I2C_SAR[2:1],
I2C_XSAR[7:0]}.
When the register receives an address starting with F7h to F0h (I2C_SAR[7:3] = 11110b),
the I2C recognizes that a 10-bit slave addressing mode is being selected. The I2C sends an
ACK after receiving the I2C_XSAR byte (the device does not generate an interrupt at this
point). After the next byte of the address (I2C_XSAR) is received, the I2C generates an
interrupt and enters SLAVE mode.Then I2C_SAR[2:1] are used as the upper 2 bits for the
10-bit extended address. The full 10-bit address is supplied by {I2C_SAR[2:1],
I2C_XSAR[7:0]}. See Table 125.
Table 125. I2C Extended Slave Address Register (I2C_XSAR = 00C9h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
225
Bit 
Position
[7:0]
SLAX
Value
Description
00h–FFh Least-significant 8 bits of the 10-bit extended slave address
I2C Data Register
This register contains the data byte/slave address to be transmitted or the data byte just
received. In TRANSMIT mode, the MSb of the byte is transmitted first. In RECEIVE
mode, the first bit received is placed in the MSb of the register. After each byte is transmitted, the I2C_DR register contains the byte that is present on the bus in case a lost arbitration event occurs. See Table 126.
Table 126. I2C Data Register (I2C_DR = 00CAh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
DATA
Value
Description
00h–FFh
I2C data byte
I2C Control Register
The I2C_CTL register is a control register that is used to control the interrupts and the
master slave relationships on the I2C bus.
When the Interrupt Enable bit (IEN) is set to 1, the interrupt line goes High when the IFLG
is set to 1. When IEN is cleared to 0, the interrupt line always remains Low.
When the Bus Enable bit (ENAB) is set to 0, the I2C bus inputs SCLx and SDAx are
ignored and the I2C module does not respond to any address on the bus. When ENAB is
set to 1, the I2C responds to calls to its slave address and to the general call address if the
GCE bit (I2C_SAR[0]) is set to 1.
When the Master Mode Start bit (STA) is set to 1, the I2C enters MASTER mode and
sends a START condition on the bus when the bus is free. If the STA bit is set to 1 when
the I2C module is already in MASTER mode and one or more bytes are transmitted, then a
repeated START condition is sent. If the STA bit is set to 1 when the I2C block is being
accessed in SLAVE mode, the I2C completes the data transfer in SLAVE mode and then
enters MASTER mode when the bus is released. The STA bit is automatically cleared after
a START condition is set. Writing 0 to the STA bit produces no effect.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
226
If the Master Mode Stop bit (STP) is set to 1 in MASTER mode, a STOP condition is
transmitted on the I2C bus. If the STP bit is set to 1 in SLAVE mode, the I2C module operates as if a STOP condition is received, but no STOP condition is transmitted. If both STA
and STP bits are set, the I2C block first transmits the STOP condition (if in MASTER
mode), then transmits the START condition. The STP bit is cleared to 0 automatically.
Writing a 0 to this bit produces no effect.
The I2C Interrupt Flag (IFLG) is set to 1 automatically when any of 30 of the possible 31
I2C states is entered. The only state that does not set the IFLG bit is state F8h. If IFLG is
set to 1 and the IEN bit is also set, an interrupt is generated. When IFLG is set by the I2C,
the Low period of the I2C bus clock line is stretched and the data transfer is suspended.
When a 0 is written to IFLG, the interrupt is cleared and the I2C clock line is released.
When the I2C Acknowledge bit (AAK) is set to 1, an acknowledge is sent during the
acknowledge clock pulse on the I2C bus if:
•
Either the whole of a 7-bit slave address or the first or second byte of a 10-bit slave address is received.
•
The general call address is received and the General Call Enable bit in I2C_SAR is set
to 1.
•
A data byte is received while in MASTER or SLAVE modes.
When AAK is cleared to 0, a NACK is sent when a data byte is received in MASTER or
SLAVE mode. If AAK is cleared to 0 in SLAVE TRANSMIT mode, the byte in the
I2C_DR register is assumed to be the final byte. After this byte is transmitted, the I2C
block enters the C8h state, then returns to an idle state. The I2C module does not respond
to its slave address unless AAK is set to 1. See Table 127 on page 226.
Table 127. I2C Control Register (I2C_CTL = 00CBh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R
R
CPU Access
Note: R/W = Read/Write; R = Read Only.
Bit 
Position
Value Description
7
IEN
0
I2C interrupt is disabled.
1
I2C interrupt is enabled.
6
ENAB
0
The I2C bus (SCL/SDA) is disabled and all inputs are ignored.
1
The I2C bus (SCL/SDA) is enabled.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
227
Bit 
Position
Value Description
5
STA
0
Master mode START condition is sent.
1
Master mode start-transmit START condition on the bus.
4
STP
0
Master mode STOP condition is sent.
1
Master mode stop-transmit STOP condition on the bus.
3
IFLG
0
I2C interrupt flag is not set.
1
I2C interrupt flag is set.
2
AAK
0
Not Acknowledge.
1
Acknowledge.
[1:0]
00
Reserved.
I2C Status Register
The I2C_SR register is a Read Only register that contains a 5-bit status code in the five
MSbs; the three LSbs are always 0. The Read Only I2C_SR registers share the same I/
O addresses as the Write Only I2C_CCR registers. See Table 128.
Table 128. I2C Status Registers (I2C_SR = 00CCh)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
1
1
1
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read only.
Bit 
Position
Value
Description
[7:3]
STAT
00000–
11111
5-bit I2C status code.
[2:0]
000
Reserved.
There are 29 possible status codes, as listed in Table 129. When the I2C_SR register
contains the status code F8h, no relevant status information is available, no interrupt is
generated, and the IFLG bit in the I2C_CTL register is not set. All other status codes
correspond to a defined state of the I2C.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
228
When each of these states is entered, the corresponding status code appears in this register
and the IFLG bit in the I2C_CTL register is set to 1. When the IFLG bit is cleared, the status code returns to F8h.
Table 129. I2C Status Codes
Code
Status
00h
Bus error.
08h
START condition transmitted.
10h
Repeated START condition transmitted.
18h
Address and Write bit transmitted, ACK received.
20h
Address and Write bit transmitted, ACK not received.
28h
Data byte transmitted in MASTER mode, ACK received.
30h
Data byte transmitted in MASTER mode, ACK not received.
38h
Arbitration lost in address or data byte.
40h
Address and Read bit transmitted, ACK received.
48h
Address and Read bit transmitted, ACK not received.
50h
Data byte received in MASTER mode, ACK transmitted.
58h
Data byte received in MASTER mode, NACK transmitted.
60h
Slave address and Write bit received, ACK transmitted.
68h
Arbitration lost in address as master, slave address and Write bit received, ACK transmitted.
70h
General Call address received, ACK transmitted.
78h
Arbitration lost in address as master, General Call address received, ACK transmitted.
80h
Data byte received after slave address received, ACK transmitted.
88h
Data byte received after slave address received, NACK transmitted.
90h
Data byte received after General Call received, ACK transmitted.
98h
Data byte received after General Call received, NACK transmitted.
A0h
STOP or repeated START condition received in SLAVE mode.
A8h
Slave address and Read bit received, ACK transmitted.
B0h
Arbitration lost in address as master, slave address and Read bit received, ACK transmitted.
B8h
Data byte transmitted in SLAVE mode, ACK received.
C0h
Data byte transmitted in SLAVE mode, ACK not received.
C8h
Last byte transmitted in SLAVE mode, ACK received.
D0h
Second Address byte and Write bit transmitted, ACK received.
PS019215-0910
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
229
Table 129. I2C Status Codes (Continued)
Code
Status
D8h
Second Address byte and Write bit transmitted, ACK not received.
F8h
No relevant status information, IFLG = 0.
If an illegal condition occurs on the I2C bus, the bus error state is entered (status code
00h). To recover from this state, the STP bit in the I2C_CTL register must be set and the
IFLG bit cleared. The I2C then returns to an idle state. No STOP condition is transmitted
on the I2C bus.
Note:
The STP and STA bits are set to 1 at the same time to recover from the bus error. The I2C
then sends a START condition.
I2C Clock Control Register
The I2C_CCR register is a Write Only register. The seven LSBs control the frequency at
which the I2C bus is sampled and the frequency of the I2C clock line (SCL) when the I2C
is in MASTER mode. The Write Only I2C_CCR registers share the same I/O addresses as
the Read Only I2C_SR registers. See Table 130.
Table 130. I2C Clock Control Registers (I2C_CCR = 00CCh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Read only.
Bit 
Position
Value
Description
7
0
Reserved.
[6:3]
M
0000–1111 I2C clock divider scalar value.
[2:0]
N
000–111
I2C clock divider exponent.
The I2C clocks are derived from the system clock of the eZ80F91 device. The frequency
of this system clock is fSCK. The I2C bus is sampled by the I2C block at the frequency
fSAMP supplied by the following equation:
fSAMP
PS019215-0910
=
fSCLK
2N
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
230
In MASTER mode, the I2C clock output frequency on SCL (fSCL) is supplied by the following equation:
fSCL =
fSCLK
10 • (M + 1)(2)N
The use of two separately-programmable dividers allows the MASTER mode output
frequency to be set independently of the frequency at which the I2C bus is sampled. This
feature is particularly useful in multimaster systems because the frequency at which the
I2C bus is sampled must be at least 10 times the frequency of the fastest master on the bus
to ensure that START and STOP conditions are always detected. By using two
programmable clock divider stages, a high sampling frequency is ensured while allowing
the MASTER mode output to be set to a lower frequency.
Bus Clock Speed
The I2C bus is defined for bus clock speeds up to 100 kbps (400 kbps in FAST mode).
To ensure correct detection of START and STOP conditions on the bus, the I2C must sample the I2C bus at least ten times faster than the bus clock speed of the fastest master on the
bus. The sampling frequency must therefore be at least 1 MHz (4 MHz in FAST mode) to
guarantee correct operation with other bus masters.
The I2C sampling frequency is determined by the frequency of the eZ80F91 system clock
and the value in the I2C_CCR bits 2 to 0. The bus clock speed generated by the I2C in
MASTER mode is determined by the frequency of the input clock and the values in
I2C_CCR[2:0] and I2C_CCR[6:3].
I2C Software Reset Register
The I2C_SRR register is a Write Only register. Writing any value to this register performs
a software reset of the I2C module. See Table 131.
Table 131. I2C Software Reset Register (I2C_SRR = 00CDh)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
Value
[7:0]
SRR
00h–FFh Writing any value to this register performs a software reset
of the I2C module.
PS019215-0910
Description
I2C Serial I/O Interface
eZ80F91 MCU
Product Specification
231
Zilog Debug Interface
Introduction
The Zilog Debug Interface (ZDI) provides a built-in debugging interface to the CPU. ZDI
provides basic in-circuit emulation features including:
•
•
•
•
•
•
•
•
•
Examining and modifying internal registers.
Examining and modifying memory.
Starting and stopping the user program.
Setting program and data break points.
Single-stepping the user program.
Executing user-supplied instructions.
Debugging the final product with the inclusion of one small connector.
Downloading code into SRAM.
C source-level debugging using Zilog Developer Studio II (ZDS II).

The above features are built into the silicon. Control is provided via a two-wire interface
that is connected to the USB Smart Cable emulator. Figure 48 displays a typical setup
using a a target board, USB Smart Cable, and the host PC running Zilog Developer Studio
II. For more information on USB Smart Cable and ZDS II, refer to www.zilog.com.
Target Board
Zilog
Developer
Studio
USB Smart
Cable
Emulator
C
O
N
N
E
C
T
O
R
eZ80®
Product
Figure 48. Typical ZDI Debug Setup
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
232
ZDI allows reading and writing of most internal registers without disturbing the state of
the machine. Reads and Writes to memory occurs as fast as the ZDI downloads and
uploads data, with a maximum supported ZDI clock frequency of 0.4 times the eZ80F91
system clock frequency. Also, regardless of the ZDI clock frequency, the duration of the
low-phase of the ZDI clock (that is, ZCL = 0) must be at least 1.25 times the system clock
period.
For the description on how to enable the ZDI interface on the exit of RESET, see the OCI
Activation on page 258.
Table 132. Recommend ZDI Clock versus System Clock Frequency
System Clock Frequency
ZDI Clock Frequency
3–10 MHz
1 MHz
8–16 MHz
2 MHz
12–24 MHz
4 MHz
20–50 MHz
8 MHz
ZDI-Supported Protocol
ZDI supports a bidirectional serial protocol. The protocol defines any device that sends
data as the transmitter and any receiving device as the receiver. The device controlling the
transfer is the master and the device being controlled is the slave. The master always initiates the data transfers and provides the clock for both receive and transmit operations.
The ZDI block on the eZ80F91 device is considered a slave in all data transfers.
Figure 49 on page 233 displays the schematic for building a connector on a target board.
This connector allows you to connect directly to the USB Smart Cable emulator using a
six-pin header.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
233
TVDD
(Target VDD )
10 Kohm
eZ80F91
10 Kohm
TCK (ZCL)
TDI (ZDA)
2
1
4
3
6
5
6-Pin Target Connector
Figure 49. Schematic For Building a Target Board USB Smart Cable
Connector
ZDI Clock and Data Conventions
The two pins used for communication with the ZDI block are the ZDI clock pin (ZCL) and
the ZDI data pin (ZDA). On eZ80F91, the ZCL pin is shared with the TCK pin while the
ZDA pin is shared with the TDI pin. The ZCL and ZDA pin functions are only available
when the On-Chip Instrumentation is disabled and the ZDI is therefore enabled. For general data communication, the data value on the ZDA pin changes only when ZCL is Low
(0). The only exception is the ZDI START bit, which is indicated by a High-to-Low transition (falling edge) on the ZDA pin while ZCL is High.
Data is shifted into and out of ZDI, with the MSb (bit 7) of each byte being first in time,
and the LSb (bit 0) last in time. All information is passed between the master and the slave
in 8-bit (single-byte) units. Each byte is transferred with nine clock cycles; eight to shift
the data, and the ninth for internal operations.
ZDI START Condition
All ZDI commands are preceded by the ZDI START signal, which is a High-to-Low transition of ZDA when ZCL is High. The ZDI slave on the eZ80F91 device continually monitors the ZDA and ZCL lines for the START signal and does not respond to any command
until this condition is met. The master pulls ZDA Low, with ZCL High, to indicate the
beginning of a data transfer with the ZDI block. Figure 50 on page 234 and Figure 51 on
page 234 displays a valid ZDI START signal prior to writing and reading data, respectively. A Low-to-High transition of ZDA while the ZCL is High produces no effect.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
234
Data is shifted in during a Write to the ZDI block on the rising edge of ZCL, as displayed
in Figure 50. Data is shifted out during a Read from the ZDI block on the falling edge of
ZCL as displayed in Figure 51. When an operation is completed, the master stops during
the ninth cycle and holds the ZCL signal High.
ZDI Data In
(Write)
ZDI Data In
(Write)
ZCL
ZDA
Start Signal
Figure 50. ZDI Write Timing
ZDI Data Out
(Read)
ZDI Data Out
(Read)
ZCL
ZDA
Start Signal
Figure 51. ZDI Read Timing
ZDI Single-Bit Byte Separator
Following each 8-bit ZDI data transfer, a single-bit byte separator is used. To initiate a
new ZDI command, the single-bit byte separator must be High (logical 1) to allow for a
new ZDI START command to be sent. For all other cases, the single-bit byte separator is
either Low (logical 0) or High (logical 1). When ZDI is configured to allow the CPU to
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
235
accept external bus requests, the single-bit byte separator must be Low (logical 0) during
all ZDI commands. This Low value indicates that ZDI is still operating and is not ready to
relinquish the bus. The CPU does not accept the external bus requests until the single-bit
byte separator is a High (logical 1). For more information on accepting bus requests in
ZDI DEBUG mode, see Bus Requests During ZDI Debug Mode on page 238.
ZDI Register Addressing
Following a START signal the ZDI master must output the ZDI register address. All data
transfers with the ZDI block use special ZDI registers. The ZDI control registers that
reside in the ZDI register address space must not be confused with the eZ80F91 device
peripheral registers that reside in the I/O address space.
Many locations in the ZDI control register address space are shared by two registers—one
for Read Only access and one for Write Only access. For example, a Read from ZDI register address 00h returns the eZ80® Product ID Low Byte, while a Write to this same location, 00h, stores the Low byte of one of the address match values used for generating
break points.
The format for a ZDI address is seven bits of address, followed by one bit for Read or
Write control, and completed by a single-bit byte separator. The ZDI executes a Read or
Write operation depending on the state of the R/W bit (0 = Write, 1 = Read). If no new
START command is issued at completion of the Read or Write operation, the operation is
repeated. This allows repeated Read or Write operations without having to resend the ZDI
command. A START signal must follow to initiate a new ZDI command. Figure 52 displays the timing for address Writes to ZDI registers.
Single-Bit
Byte Separator
or new ZDI
START Signal
ZDI Address Byte
ZCL
S
ZDA
1
2
3
4
5
6
7
8
A6
A5
A4
A3
A2
A1
A0
R/W
msb
9
0/1
lsb
0 = WRITE
1 = READ
START
Signal
Figure 52. ZDI Address Write Timing
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
236
ZDI Write Operations
ZDI Single-Byte Write
For single-byte Write operations, the address and write control bit are first written to the
ZDI block. Following the single-bit byte separator, the data is shifted into the ZDI block
on the next 8 rising edges of ZCL. The master terminates activity after 8 clock cycles.
Figure 53 displays the timing for ZDI single-byte Write operations.
ZDI Data Byte
ZCL
7
8
9
1
2
3
4
5
6
7
8
ZDA
A0
Write
0/1
D7
D6
D5
D4
D3
D2
D1
D0
msb
of DATA
lsb of
ZDI Address
Single-Bit
Byte Separator
9
1
lsb
of DATA
End of Data
or New ZDI
START Signal
Figure 53. ZDI Single-Byte Data Write Timing
ZDI Block Write
The block Write operation is initiated in the same manner as the single-byte Write operation, but instead of terminating the Write operation after the first data byte is transferred,
the ZDI master continues to transmit additional bytes of data to the ZDI slave on the
eZ80F91 device. After the receipt of each byte of data the ZDI register address increments
by 1. If the ZDI register address reaches the end of the Write Only ZDI register address
space (30h), the address stops incrementing. Figure 54 displays the timing for ZDI block
Write operations.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
237
ZDI Data Bytes
ZCL
7
8
9
1
2
3
7
8
9
1
2
ZDA
A0
Write
0/1
D7
D6
D5
D1
D0
0/1
D7
D6
msb
of DATA
Byte 1
lsb
of DATA
Byte 1
Single-Bit
Byte Separator
lsb of
ZDI Address
9
1
msb
of DATA
Byte 2
Single-Bit
Byte Separator
Figure 54. ZDI Block Data Write Timing
ZDI Read Operations
ZDI Single-Byte Read
Single-byte Read operations are initiated in the same manner as single-byte Write operations, with the exception that the R/W bit of the ZDI register address is set to 1. Upon
receipt of a slave address with the R/W bit set to 1, the eZ80F91 device’s ZDI block loads
the selected data into the shifter at the beginning of the first cycle following the single-bit
data separator. The most significant bit (msb) is shifted out first. Figure 55 displays the
timing for ZDI single-byte Read operations.
ZDI Data Byte
ZCL
7
8
9
1
2
3
4
5
6
7
8
ZDA
A0
Read
0/1
D7
D6
D5
D4
D3
D2
D1
D0
msb
of DATA
lsb of
ZDI Address
Single-Bit
Byte Separator
9
1
lsb
of DATA
End of Data
or New ZDI
START Signal
Figure 55. ZDI Single-Byte Data Read Timing
Note:
PS019215-0910
In ZDI single-byte read operations, after each read operation, the Program Counter (PC)
address is incremented by two bytes. For example, if the current PC address is 0x00, then
Zilog Debug Interface
eZ80F91 MCU
Product Specification
238
a read operation at 0x00 increments the PC to 0x02. To read the next byte, the PC must be
decremented by one.
ZDI Block Read
A block Read operation is initiated in the same manner as a single-byte Read; however,
the ZDI master continues to clock in the next byte from the ZDI slave as the ZDI slave
continues to output data. The ZDI register address counter increments with each Read. If
the ZDI register address reaches the end of the Read Only ZDI register address space
(20h), the address stops incrementing. Figure 56 displays the ZDI’s block Read timing.
ZDI Data Bytes
ZCL
7
8
9
1
2
3
7
8
9
1
2
ZDA
A0
Read
0/1
D7
D6
D5
D1
D0
0/1
D7
D6
msb
of DATA
Byte 1
lsb of
ZDI Address
Single-Bit
Byte Separator
lsb
of DATA
Byte 1
9
1
msb
of DATA
Byte 2
Single-Bit
Byte Separator
Figure 56. ZDI Block Data Read Timing
Operation of the eZ80F91 Device during ZDI Break Points
If the ZDI forces the CPU to break, only the CPU suspends operation. The system clock
continues to operate and drive other peripherals. Those peripherals that operate autonomously from the CPU continues to operate, if so enabled. For example, the Watchdog
Timer and Programmable Reload Timers continue to count during a ZDI break point.
When using the ZDI interface, any Write or Read operations of peripheral registers in the
I/O address space produces the same effect as Read or Write operations using the CPU. As
many register Read/Write operations exhibit secondary effects, such as clearing flags or
causing operations to commence, the effects of the Read/Write operations during a ZDI
break must be taken into consideration.
Bus Requests During ZDI Debug Mode
The ZDI block on the eZ80F91 device allows an external device to take control of the
address and data bus while the eZ80F91 device is in DEBUG mode. ZDI_BUSACK_EN
causes ZDI to allow or prevent acknowledgement of bus requests by external peripherals.
The bus acknowledge occurs only at the end of the current ZDI operation (indicated by a
High during the single-bit byte separator). The default reset condition is for bus acknowl-
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
239
edgement to be disabled. To allow bus acknowledgement, the ZDI_BUSACK_EN must be
written.
When an external bus request (BUSREQ pin asserted) is detected, ZDI waits until completion of the current operation before responding. ZDI acknowledges the bus request by
asserting the bus acknowledge (BUSACK) signal. If the ZDI block is not currently shifting data, it acknowledges the bus request immediately. ZDI uses the single-bit byte separator of each data word to determine if it is at the end of a ZDI operation. If the bit is a
logical 0, ZDI does not assert BUSACK to allow additional data Read or Write operations.
If the bit is a logical 1, indicating completion of the ZDI commands, BUSACK is asserted.
Potential Hazards of Enabling Bus Requests During DEBUG Mode
There are some potential hazards that you must be aware of when enabling external bus
requests during ZDI DEBUG mode. First, when the address and data bus are being used
by an external source, ZDI must only access ZDI registers and internal CPU registers to
prevent possible bus contention. The bus acknowledge status is reported in the
ZDI_BUS_STAT register. The BUSACK output pin also indicates the bus acknowledge
state.
A second hazard is that when a bus acknowledge is granted, the ZDI is subject to any wait
states that are assigned to the device currently being accessed by the external peripheral.
To prevent data errors, ZDI must avoid data transmission while another device is
controlling the bus.
Finally, exiting ZDI DEBUG mode while an external peripheral controls the address and
data buses, as indicated by BUSACK assertion produces unpredictable results.
ZDI Write Only Registers
Table 133 lists the ZDI Write Only registers. Many of the ZDI Write Only addresses are
shared with ZDI Read Only registers.
Table 133. ZDI Write Only Registers
PS019215-0910
ZDI Address
ZDI Register Name
ZDI Register Function
Reset
Value
00h
ZDI_ADDR0_L
Address Match 0 Low Byte
XXh
01h
ZDI_ADDR0_H
Address Match 0 High Byte
XXh
02h
ZDI_ADDR0_U
Address Match 0 Upper Byte
XXh
04h
ZDI_ADDR1_L
Address Match 1 Low Byte
XXh
05h
ZDI_ADDR1_H
Address Match 1 High Byte
XXh
06h
ZDI_ADDR1_U
Address Match 1 Upper Byte
XXh
Zilog Debug Interface
eZ80F91 MCU
Product Specification
240
Table 133. ZDI Write Only Registers (Continued)
ZDI Address
ZDI Register Name
ZDI Register Function
Reset
Value
08h
ZDI_ADDR2_L
Address Match 2 Low Byte
XXh
09h
ZDI_ADDR2_H
Address Match 2 High Byte
XXh
0Ah
ZDI_ADDR2_U
Address Match 2 Upper Byte
XXh
0Ch
ZDI_ADDR3_L
Address Match 3 Low Byte
XXh
0Dh
ZDI_ADDR3_H
Address Match 3 High Byte
XXh
0Eh
ZDI_ADDR3_U
Address Match 4 Upper Byte
XXh
10h
ZDI_BRK_CTL
Break Control Register
00h
11h
ZDI_MASTER_CTL
Master Control Register
00h
13h
ZDI_WR_DATA_L
Write Data Low Byte
XXh
14h
ZDI_WR_DATA_H
Write Data High Byte
XXh
15h
ZDI_WR_DATA_U
Write Data Upper Byte
XXh
16h
ZDI_RW_CTL
Read/Write Control Register
00h
17h
ZDI_BUS_CTL
Bus Control Register
00h
21h
ZDI_IS4
Instruction Store 4
XXh
22h
ZDI_IS3
Instruction Store 3
XXh
23h
ZDI_IS2
Instruction Store 2
XXh
24h
ZDI_IS1
Instruction Store 1
XXh
25h
ZDI_IS0
Instruction Store 0
XXh
30h
ZDI_WR_MEM
Write Memory Register
XXh
ZDI Read Only Registers
Table 134 lists the ZDI Read Only registers. Many of the ZDI Read Only addresses are
shared with ZDI Write Only registers.
Table 134. ZDI Read Only Registers
ZDI Address
ZDI Register Name
ZDI Register Function
Reset
Value
00h
ZDI_ID_L
eZ80® Product ID Low Byte Register
08h
01h
ZDI_ID_H
eZ80 Product ID High Byte Register
00h
02h
ZDI_ID_REV
eZ80 Product ID Revision Register
XXh
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
241
Table 134. ZDI Read Only Registers (Continued)
ZDI Address
ZDI Register Name
ZDI Register Function
Reset
Value
03h
ZDI_STAT
Status Register
00h
10h
ZDI_RD_L
Read Memory Address Low Byte Register
XXh
11h
ZDI_RD_H
Read Memory Address High Byte Register
XXh
12h
ZDI_RD_U
Read Memory Address Upper Byte Register
XXh
17h
ZDI_BUS_STAT
Bus Status Register
00h
20h
ZDI_RD_MEM
Read Memory Data Value
XXh
ZDI Register Definitions
ZDI Address Match Registers
The four sets of address match registers are used for setting the addresses for generating
break points. When the accompanying BRK_ADDRX bit is set in the ZDI Break Control
register to enable the particular address match, the current eZ80F91 address is compared
with the 3-byte address set, {ZDI_ADDRx_U, ZDI_ADDRx_H, and ZDI_ADDR_x_L}.
If the CPU is operating in ADL mode, the address is supplied by ADDR[23:0]. If the CPU
is operating in Z80® mode, the address is supplied by {MBASE[7:0], ADDR[15:0]}. If a
match is found, ZDI issues a break to the eZ80F91 device placing the CPU in ZDI mode
pending further instructions from the ZDI interface block. If the address is not the first opcode fetch, the ZDI break is executed at the end of the instruction in which it is executed.
There are four sets of address match registers. They are used in conjunction with each
other to break on branching instructions. See Table 135 on page 241.
Table 135. ZDI Address Match Registers
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
[7:0]
zdi_addrx_l,
zdi_addrx_h,
or 
zdi_addrx_u
PS019215-0910
Value
Description
00h–FFh The four sets of ZDI address match registers are used for
setting the addresses for generating break points. The 24
bit addresses are supplied by {ZDI_ADDRx_U,
ZDI_ADDRx_H, ZDI_ADDRx_L, where x is 0, 1, 2, or 3.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
242
Address Information for ZDI Address Match Registers
ZDI_ADDR0_L = 00h, ZDI_ADDR0_H = 01h, ZDI_ADDR0_U = 02h, ZDI_ADDR1_L =
04h, ZDI_ADDR1_H = 05h, ZDI_ADDR1_U = 06h, ZDI_ADDR2_L = 08h, ZDI_ADDR2_H
= 09h, ZDI_ADDR2_U = 0Ah, ZDI_ADDR3_L = 0Ch, ZDI_ADDR3_H = 0Dh, and
ZDI_ADDR3_U = 0Eh in the ZDI Register Write Only Address Space.
ZDI Break Control Register
The ZDI Break Control register is used to enable break points. ZDI asserts a break when
the CPU instruction address, ADDR[23:0], matches the value in the ZDI Address Match 3
registers, {ZDI_ADDR3_U, ZDI_ADDR3_H, ZDI_ADDR3_L}. BREAKs occurs only
on an instruction boundary. If the instruction address is not the beginning of an instruction
(that is, for multibyte instructions), then the break occurs at the end of the current instruction. The brk_next bit is set to 1. The brk_next bit must be reset to 0 to release the break.
See Table 136 on page 243.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
243
Table 136. ZDI Break Control Register (ZDI_BRK_CTL = 10h in the ZDI Write Only Register
Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
7
brk_next
6
brk_addr3
5
brk_addr2
4
brk_addr1
3
brk_addr0
PS019215-0910
Value Description
0
The ZDI break on the next CPU instruction is disabled.
Clearing this bit releases the CPU from its current BREAK
condition.
1
The ZDI break on the next CPU instruction is enabled. The
CPU uses multibyte Op Codes and multibyte operands.
Break points only occur on the first Op Code in a multibyte
Op Code instruction. If the ZCL pin is High and the ZDA pin
is Low at the end of RESET, this bit is set to 1 and a break
occurs on the first instruction following the RESET. This bit
is set automatically during ZDI break on address match. A
break is also forced by writing a 1 to this bit.
0
The ZDI break, upon matching break address 3, is
disabled.
1
The ZDI break, upon matching break address 3, is
enabled.
0
The ZDI break, upon matching break address 2, is
disabled.
1
The ZDI break, upon matching break address 2, is
enabled.
0
The ZDI break, upon matching break address 1, is
disabled.
1
The ZDI break, upon matching break address 1, is
enabled.
0
The ZDI break, upon matching break address 0, is
disabled.
1
The ZDI break, upon matching break address 0, is
enabled.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
244
Bit 
Position
2
ign_low_1
1
ign_low_0
0
single_step
PS019215-0910
Value Description
0
The Ignore the Low Byte function of the ZDI Address Match
1 registers is disabled. If brk_addr1 is set to 1, ZDI initiates
a break when the entire 24-bit address, ADDR[23:0],
matches the 3-byte value {ZDI_ADDR1_U,
ZDI_ADDR1_H, ZDI_ADDR1_L}.
1
The Ignore the Low Byte function of the ZDI Address Match
1 registers is enabled. If brk_addr1 is set to 1, ZDI initiates
a break when only the upper 2 bytes of the 24-bit address,
ADDR[23:8], match the 2-byte value {ZDI_ADDR1_U,
ZDI_ADDR1_H}. As a result, a break occurs anywhere
within a 256-byte page.
0
The Ignore the Low Byte function of the ZDI Address Match
1 registers is disabled. If brk_addr0 is set to 1, ZDI initiates
a break when the entire 24-bit address, ADDR[23:0],
matches the 3-byte value {ZDI_ADDR0_U,
ZDI_ADDR0_H, ZDI_ADDR0_L}.
1
The Ignore the Low Byte function of the ZDI Address Match
1 registers is enabled. If the brk_addr1 is set to 0, ZDI
initiates a break when only the upper 2 bytes of the 24-bit
address, ADDR[23:8], match the 2 bytes value
{ZDI_ADDR0_U, ZDI_ADDR0_H}. As a result, a break
occurs anywhere within a 256-byte page.
0
ZDI single step mode is disabled.
1
ZDI single step mode is enabled. ZDI asserts a break
following execution of each instruction.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
245
ZDI Master Control Register
The ZDI Master Control register provides control of the eZ80F91 device. It is capable of
forcing a RESET and waking up the eZ80F91 from the LOW-POWER modes (HALT or
SLEEP). See Table 137.
Table 137. ZDI Master Control Register (ZDI_MASTER_CTL = 11h in ZDI Register Write
Address Spaces)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
Value
Description
7
ZDI_RESET
0
No action.
1
Initiate a RESET of the eZ80F91. This bit is automatically
cleared at the end of the RESET event.
[6:0]
0000000 Reserved.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
246
ZDI Write Data Registers
These three registers are used in the ZDI Write Only register address space to store the
data that is written when a Write instruction is sent to the ZDI Read/Write Control register
(ZDI_RW_CTL). The ZDI Read/Write Control register is located at ZDI address 16h
immediately following the ZDI Write Data registers. As a result, the ZDI Master is
allowed to write the data to {ZDI_WR_U, ZDI_WR_H, ZDI_WR_L} and the Write
command in one data transfer operation. See Table 138.
Table 138. ZDI Write Data Registers (ZDI_WR_U = 13h, ZDI_WR_H = 14h, and ZDI_WR_L =
15h in the ZDI Register Write Only Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: X = Undefined; W = Write.
Bit 
Position
[7:0]
zdi_wr_l,
zdi_wr_h,
or
zdi_wr_l
PS019215-0910
Value
Description
00h–FFh
These registers contain the data that is written during
execution of a Write operation defined by the
ZDI_RW_CTL register. The 24-bit data value is stored
as {ZDI_WR_U, ZDI_WR_H, ZDI_WR_L}. If less than
24 bits of data are required to complete the required
operation, the data is taken from the LSBs.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
247
ZDI Read/Write Control Register
The ZDI Read/Write Control register is used in the ZDI Write Only Register address to
read data from, write data to, and manipulate the CPU’s registers or memory locations.
When this register is written, the eZ80F91 device immediately performs the operation
corresponding to the data value written as listed in Table 139. When a Read operation is
executed via this register, the requested data values are placed in the ZDI Read Data
registers {ZDI_RD_U, ZDI_RD_H, ZDI_RD_L}. When a Write operation is executed via
this register, the Write data is taken from the ZDI Write Data registers {ZDI_WR_U,
ZDI_WR_H, ZDI_WR_L}. See Table 139. For information on the CPU registers, refer to
eZ80® CPU User Manual (UM0077) available on www.zilog.com.
The CPU’s alternate register set (A’, F’, B’, C’, D’, E’, HL’) cannot be read directly. The
ZDI programmer must execute the exchange instruction (EXX) to gain access to the alternate CPU register set.
Note:
Table 139. ZDI Read/Write Control Register Functions (ZDI_RW_CTL = 16h in the ZDI
Register Write Only Address Space)
Hex
Value
Command
Hex
Value
Command
00
Read {MBASE, A, F}
ZDI_RD_UMBASE
ZDI_RD_HF
ZDI_RD_LA
80
Write AF
MBASEZDI_WR_U
FZDI_WR_H
AZDI_WR_L
01
Read BC
ZDI_RD_UBCU
ZDI_RD_HB
ZDI_RD_LC
81
Write BC
BCUZDI_WR_U
BZDI_WR_H
CZDI_WR_L
02
Read DE
ZDI_RD_UDEU
ZDI_RD_HD
ZDI_RD_LE
82
Write DE
DEUZDI_WR_U
DZDI_WR_H
EZDI_WR_L
03
Read HL
ZDI_RD_UHLU
ZDI_RD_HH
ZDI_RD_LL
83
Write HL
HLUZDI_WR_U
HZDI_WR_H
LZDI_WR_L
04
Read IX
ZDI_RD_UIXU
ZDI_RD_HIXH
ZDI_RD_LIXL
84
Write IX
IXUZDI_WR_U
IXHZDI_WR_H
IXLZDI_WR_L
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
248
Table 139. ZDI Read/Write Control Register Functions (ZDI_RW_CTL = 16h in the ZDI
Register Write Only Address Space) (Continued)
Hex
Value
Command
Hex
Value
Command
05
Read IY
ZDI_RD_UIYU
ZDI_RD_HIYH
ZDI_RD_LIYL
85
Write IY
IYUZDI_WR_U
IYHZDI_WR_H
IYLZDI_WR_L
06
Read SP
In ADL mode, SP = SPL.
In Z80® mode, SP = SPS.
86
Write SP
In ADL mode, SP = SPL.
In Z80 mode, SP = SPS.
07
Read PC
ZDI_RD_UPC[23:16]
ZDI_RD_HPC[15:8]
ZDI_RD_LPC[7:0]
87
Write PC
PC[23:16]ZDI_WR_U
PC[15:8]ZDI_WR_H
PC[7:0]ZDI_WR_L
08
Set ADL
ADL1
88
Reserved
09
Reset ADL
ADL 0
89
Reserved
0A
Exchange CPU register sets
AF AF’
BC BC’
DE DE’
HL HL’
8A
Reserved
0B
Read memory from current PC 8B
value, increment PC
PS019215-0910
Write memory from current PC
value, increment PC
Zilog Debug Interface
eZ80F91 MCU
Product Specification
249
ZDI Bus Control Register
The ZDI Bus Control register controls bus requests during DEBUG mode. It enables or
disables bus acknowledge in ZDI DEBUG mode and allows ZDI to force assertion of the
BUSACK signal. This register must only be written during ZDI DEBUG mode (that is,
following a break). See Table 140.
Table 140. ZDI Bus Control Register (ZDI_BUS_CTL = 17h in the ZDI Register Write Only
Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write Only.
Bit 
Position
7
ZDI_BUSAK_EN
6
ZDI_BUSAK
[5:0]
Value
Description
0
Bus requests by external peripherals using the BUSREQ
pin are ignored. The bus acknowledge signal, BUSACK, is
not asserted in response to any bus requests.
1
Bus requests by external peripherals using the BUSREQ
pin are accepted. A bus acknowledge occurs at the end of
the current ZDI operation. The bus acknowledge is
indicated by asserting the BUSACK pin in response to a
bus request.
0
Deassert the bus acknowledge pin (BUSACK) to return
control of the address and data buses back to ZDI.
1
Assert the bus acknowledge pin (BUSACK) to pass control
of the address and data buses to an external peripheral.
000000
Reserved.
Instruction Store 4:0 Registers
The ZDI Instruction Store registers are located in the ZDI Register Write Only address
space. They are written with instruction data for direct execution by the CPU. When the
ZDI_IS0 register is written, the eZ80F91 device exits the ZDI break state and executes a
single instruction. The opcodes and operands for the instruction come from these Instruction Store registers. The Instruction Store Register 0 is the first byte fetched, followed by
Instruction Store registers 1, 2, 3, and 4, as necessary. Only the bytes the CPU requires to
execute the instruction must be stored in these registers. Some CPU instructions, when
combined with the MEMORY mode suffixes (.SIS, .SIL, .LIS, or .LIL), require 6 bytes to
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
250
operate. These 6-byte instructions cannot be executed directly using the ZDI Instruction
Store registers. See Table 141.
Note:
The Instruction Store 0 register is located at a higher ZDI address than the other Instruction Store registers. This feature allows the use of the ZDI auto-address increment function
to load and execute a multibyte instruction with a single data stream from the ZDI master.
Execution of the instruction commences with writing the final byte to ZDI_IS0.
Table 141. Instruction Store 4:0 Registers (ZDI_IS4 = 21h, ZDI_IS3 = 22h, ZDI_IS2 = 23h,
ZDI_IS1 = 24h, and ZDI_IS0 = 25h in the ZDI Register Write Only Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: X = Undefined; W = Write.
Bit 
Position
[7:0]
zdi_is4,
zdi_is3,
zdi_is2,
zdi_is1, 
or
zdi_is0
Value
Description
00h–FFh These registers contain the Op Codes and operands for
immediate execution by the CPU following a Write to
ZDI_IS0. The ZDI_IS0 register contains the first Op Code
of the instruction. The remaining ZDI_ISx registers
contain any additional Op Codes or operand dates
required for execution of the required instruction.
ZDI Write Memory Register
A Write to the ZDI Write Memory register causes the eZ80F91 device to write the 8-bit
data to the memory location specified by the current address in the Program Counter. In
Z80® MEMORY mode, this address is {MBASE, PC[15:0]}. In ADL MEMORY mode,
this address is PC[23:0]. The Program Counter, PC, increments after each data Write.
However, the ZDI register address does not increment automatically when this register
is accessed. As a result, the ZDI master is allowed to write any number of data bytes by
writing to this address one time followed by any number of data bytes. See Table 142
on page 251.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
251
Table 142. ZDI Write Memory Register (ZDI_WR_MEM = 30h in the ZDI Register Write Only
Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
W
W
W
W
W
W
W
W
Note: X = Undefined; W = Write.
Bit 
Position
Value
[7:0]
zdi_wr_mem
Description
00h–FFh The 8-bit data that is transferred to the ZDI slave
following a Write to this address is written to the address
indicated by the current Program Counter. The Program
Counter is incremented following each 8 bits of data. In
Z80® MEMORY mode, ({MBASE, PC[15:0]}) 8 bits of
transferred data. In ADL MEMORY mode, (PC[23:0]) 
8-bits of transferred data.
eZ80® Product ID Low and High Byte Registers
The eZ80 Product ID Low and High Byte registers combine to provide a means for an
external device to determine the particular eZ80 product being addressed. See Table 143
and Table 144 on page 252.
Table 143. eZ80 Product ID Low Byte Register (ZDI_ID_L = 00h in the ZDI Register Read Only
Address Space, ZDI_ID_L = 0000h in the I/O Register Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
1
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
zdi_id_l
PS019215-0910
Value Description
08h
{ZDI_ID_H, ZDI_ID_L} = {00h, 08h} indicates the eZ80F91
product.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
252
Table 144. eZ80® Product ID High Byte Register (ZDI_ID_H = 01h in the ZDI Register Read Only
Address Space, ZDI_ID_H = 0001h in the I/O Register Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
zdi_id_H
Value Description
00h
{ZDI_ID_H, ZDI_ID_L} = {00h, 08h} indicates the eZ80F91
device.
eZ80 Product ID Revision Register
The eZ80 Product ID Revision register identifies the current revision of the eZ80F91
product. See Table 145.
Table 145. eZ80 Product ID Revision Register (ZDI_ID_REV = 02h in the ZDI Register Read
Only Address Space, ZDI_ID_REV = 0002h in the I/O Register Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
CPU Access
R
R
R
R
R
R
R
R
Note: X = Undetermined; R = Read Only.
Bit 
Position
[7:0]
zdi_id_rev
PS019215-0910
Value
Description
00h–FFh Identifies the current revision of the eZ80F91 product.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
253
ZDI Status Register
The ZDI Status register provides current information on the eZ80F91 device and the CPU.
See Table 146.
Table 146. ZDI Status Register (ZDI_STAT = 03h in the ZDI Register Read Only Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
Value Description
7
zdi_active
0
The CPU is not functioning in ZDI mode.
1
The CPU is currently functioning in ZDI mode.
6
0
Reserved.
5
halt_SLP
0
The CPU is not currently in HALT or SLEEP mode.
1
The CPU is currently in HALT or SLEEP mode.
4
ADL
0
The CPU is operating in Z80® MEMORY mode.
(ADL bit = 0)
1
The CPU is operating in ADL MEMORY mode.
(ADL bit = 1)
3
MADL
0
The CPU’s Mixed-Memory mode (MADL) bit is reset to 0.
1
The CPU’s Mixed-Memory mode (MADL) bit is set to 1.
2
IEF1
0
The CPU’s Interrupt Enable Flag 1 is reset to 0. Maskable
interrupts are disabled.
1
The CPU’s Interrupt Enable Flag 1 is set to 1. Maskable
interrupts are enabled.
00
Reserved.
[1:0]
Reserved
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
254
ZDI Read Register Low, High, and Upper
The ZDI register Read Only address space offers Low, High, and Upper functions, which
contain the value read by a Read operation from the ZDI Read/Write Control register
(ZDI_RW_CTL). This data is valid only while in ZDI BREAK mode and only if the
instruction is read by a request from the ZDI Read/Write Control register. See Table 147.
Table 147. ZDI Read Register Low, High, and Upper (ZDI_RD_L = 10h, ZDI_RD_H = 11h, and
ZDI_RD_U = 12h in the ZDI Register Read Only Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
zdi_rd_l,
zdi_rd_h, 
or
zdi_rd_u
PS019215-0910
Value
Description
00h–FFh Values read from the memory location as requested by the
ZDI Read Control register during a ZDI Read operation.
The 24-bit value is supplied by {ZDI_RD_U, ZDI_RD_H,
ZDI_RD_L}.
Zilog Debug Interface
eZ80F91 MCU
Product Specification
255
ZDI Bus Status Register
The ZDI Bus Status register monitors BUSACKs during DEBUG mode. See Table 148.
Table 148. ZDI Bus Control Register (ZDI_BUS_STAT = 17h in the ZDI Register Read Only
Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
7
ZDI_BUSAcK_En
6
ZDI_BUS_STAT
[5:0]
Value
Description
0
Bus requests by external peripherals using the
BUSREQ pin are ignored. The bus acknowledge signal,
BUSACK, is not asserted.
1
Bus requests by external peripherals using the
BUSREQ pin are accepted. A bus acknowledge occurs
at the end of the current ZDI operation. The bus
acknowledge is indicated by asserting the BUSACK pin.
0
Address and data buses are not relinquished to an
external peripheral. bus acknowledge is deasserted
(BUSACK pin is High).
1
Address and data buses are relinquished to an external
peripheral. bus acknowledge is asserted (BUSACK pin
is Low).
000000
Reserved.
ZDI Read Memory Register
When a Read is executed from the ZDI Read Memory register, the eZ80F91 device
fetches the data from the memory address currently pointed to by the Program
Counter, PC; the Program Counter is then incremented. In Z80® MEMORY mode, the
memory address is {MBASE, PC[15:0]}. In ADL MEMORY mode, the memory
address is PC[23:0]. For more information on Z80 and ADL MEMORY modes, refer
to the eZ80® CPU User Manual (UM0077) available on www.zilog.com. The Program Counter, PC, increments after each data Read. However, the ZDI register address
does not increment automatically when this register is accessed. As a result, the ZDI
master reads any number of data bytes out of memory via the ZDI Read Memory register. See Table 149 on page 256.
PS019215-0910
Zilog Debug Interface
eZ80F91 MCU
Product Specification
256
Note that the delay between issuing a memory read request and the return of the corresponding data amount to multiple ZDI clock cycles. This delay is a function of the wait
state configuration of the memory space being accessed as well as the relative frequencies
of the ZDI clock and the system clock. If the ZDI master begins clocking the read data out
of the eZ80F91 soon after issuing the memory read request, invalid data will be returned.
Since no data-valid handshake mechanism exists in the ZDI protocol, the ZDI master must
account for expected memory read delay in some way.
A technique exists to mask this delay in almost all situations. It always reads at least two
consecutive bytes, starting one address lower than the address of interest. In this situation,
the eZ80F91 internally prefetches the data from the second address while the ZDI master
is sending the second read request. This allows enough time for the second ZDI memory
read to return valid data. The first data byte returned to the ZDI master must be discarded
since it is invalid. Memory reads of more than two consecutive bytes will also return correct data for all but the first address.
Table 149. ZDI Read Memory Register (ZDI_RD_MEM = 20h in the ZDI Register Read Only
Address Space)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
zdi_rd_mem
PS019215-0910
Value
Description
00h–FFh 8-bit data Read from the memory address indicated by
the CPU’s Program Counter. In Z80® Memory mode, 8bit data is transferred out from address {MBASE,
PC[15:0]}. In ADL Memory mode, 8-bit data is
transferred out from address PC[23:0].
Zilog Debug Interface
eZ80F91 MCU
Product Specification
257
On-Chip Instrumentation
Introduction to On-Chip Instrumentation
On-Chip Instrumentation1 (OCI™) for the eZ80® CPU core enables powerful debugging
features. The OCI provides run control, memory and register visibility, complex break
points, and trace history features.
The OCI employs all of the functions of the Zilog Debug Interface (ZDI) as described in
the ZDI section. It also adds the following debug features:
•
Control via a 4-pin Joint Test Action Group (JTAG) port that conforms to IEEE Standard 1149.1 (Test Access Port and Boundary Scan Architecture)
•
•
Complex break point trigger functions
•
•
Trace history buffer
Break point enhancements, such as the ability to:
– Define two break point addresses that form a range
– Break on masked data values
– Start or stop trace
– Assert a trigger output signal
Software break point instruction
There are four sections to the OCI:
•
•
•
•
JTAG interface
ZDI debug control
Trace buffer memory
Complex triggers
This document contains information to activate the OCI for JTAG boundary scan register
operations. For additional information regarding OCI features, or to order OCI debug
tools, contact:
First Silicon Solutions, Inc.
www.fs2.com
1. On-Chip Instrumentation and OCI are trademarks of First Silicon Solutions, Inc.
PS019215-0910
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
258
OCI Activation
OCI features clock initialization circuitry so that external debug hardware is detected during power-up. The external debugger must drive the OCI clock pin (TCK) Low at least
two system clock cycles prior to the end of the RESET to activate the OCI block. If TCK
is High at the end of the RESET, the OCI block shuts down so that it does not draw power
in normal product operation. When the OCI is shut down, ZDI is enabled directly and is
accessed via the clock (TCK) and data (TDI) pins. For more information on ZDI, see Zilog
Debug Interface on page 231.
OCI Interface
There are six dedicated pins on the eZ80F91 for the OCI interface. Four pins—TCK,
TMS, TDI, and TDO—are required for IEEE Standard 1149.1-compliant JTAG ports. A
fifth pin, TRSTn, is optional for IEEE 1149.1 and utilized by the eZ80F91 device. The
TRIGOUT pin provides additional testability features. These six OCI pins are listed in
Table 150.
Table 150. OCI Pins
Symbol
Name
Type
Description
TCK
Clock
Input
Asynchronous to the primary eZ80F91 system clock.
The TCK period must be at least twice the system
clock period. During RESET, this pin is sampled to
select either OCI or ZDI DEBUG modes. If Low
during RESET, the OCI is enabled. If High during
RESET, the OCI is powered down and ZDI DEBUG
mode is enabled. When ZDI DEBUG mode is active,
this pin is the ZDI clock. On-chip pull-up ensures a
default value of 1 (High).
TRSTn
TAP Reset
Input
Active Low asynchronous reset for the Test Access
Port state register. On-chip pull-up ensures a default
value of 1 (High).
TMS
Test Mode Select
Input
This serial test mode input controls JTAG mode
selection. On-chip pull-up ensures a default value of
1 (High). The TMS signal is sampled on the rising
edge of the TCK signal.
TDI
Data In
Input
(OCI enabled)
Serial test data input. This pin is input-only when the
OCI is enabled. The input data is sampled on the
rising edge of the TCK signal.
I/O
(OCI disabled)
When the OCI is disabled, this pin functions as the
ZDA (ZDI Data) I/O pin. NORMAL mode, following
RESET, configures TDI as an input.
PS019215-0910
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
259
Table 150. OCI Pins (Continued)
Symbol
Name
Type
Description
TDO
Data Out
Output
The output data changes on the falling edge of the
TCK signal.
TRIGOUT
Trigger Output
Output
Generates an active High trigger pulse when valid
OCI trigger events occur. Output is open-drain when
no data is being driven out.
JTAG Boundary Scan
Introduction
This section describes coverage, implementation, and usage of the eZ80F91 boundary
scan register based on the JTAG standard. A working knowledge of the IEEE 1149.1 specification, particularly Clause 11, is required.
Pin Coverage
All pins are included in the boundary scan chain, except the following:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
PS019215-0910
TCK
TMS
TDI
TDO
TRSTN
VDD
VSS
PLL_VDD
PLL_VSS
RTC_VDD
XIN
XOUT
RTC_XIN
RTC_XOUT
LOOP_FILT
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
260
Boundary Scan Cell Functionality
The boundary scan cells implemented are analogous to cell BC_1, defined in the Standard
VHDL Package STD_1149_1_2001.
All boundary scan cells are of the type control-and-observe; they provide both controllability and observability for the pins to which they are connected. For open-drain outputs
and bidirectional pins, this type includes controllability and observability of output
enables.
Chain Sequence and Length
When enabled to shift data, the boundary scan shift register is connected to TDI at the
input line for TRIGOUT and to TDO at PD0. The shift register is arranged so that data is
shifted via the pins starting to the left of the OCI interface pins and proceeding clockwise
around the chip. If a pin features multiple scannable bits (example: bidirectional pins or
open-drain output pins), the data is shifted first into the input signal, then the output, then
the output enable (OEN).
The boundary scan register is 213 bits wide. Table 151 lists the ordering of bits in the shift
register, numbering them in clockwise order.
Table 151. Pin to Boundary Scan Cell Mapping
Pin
Direction
Scan Cell No
TRIGOUT
Input
0
TRIGOUT
Output
TRIGOUT
Direction
Scan Cell No
MII_TxD2
Output
107
1
MII_TxD3
Output
108
OEN
2
MII_COL
Input
109
HALT_SLP
Output
3
MII_CRS
Input
110
BUSACK
Output
4
PA7
Input
111
BUSREQ
Input
5
PA7
Output
112
NMI
Input
6
PA7
OEN
113
RESET
Input
7
PA6
Input
114
Output
8
PA6
Output
115
Input
9
PA6
OEN
116
INSTRD
Output
10
PA5
Input
117
WR
Output
11
PA5
Output
118
WR
OEN
12
PA5
OEN
119
RD
Output
13
PA4
Input
120
Input
14
PA4
Output
121
RESET_OUT
WAIT
MREQ
PS019215-0910
Pin
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
261
Table 151. Pin to Boundary Scan Cell Mapping (Continued)
Pin
Direction
Scan Cell No
Pin
Direction
Scan Cell No
MREQ
Output
15
PA4
OEN
122
IORQ
Input
16
PA3
Input
123
IORQ
Output
17
PA3
Output
124
D7
Input
18
PA3
OEN
125
D7
Output
19
PA2
Input
126
D6
Input
20
PA2
Output
127
D6
Output
21
PA2
OEN
128
D5
Input
22
PA1
Input
129
D5
Output
23
PA1
Output
130
D4
Input
24
PA1
OEN
131
D4
Output
25
PA0
Input
132
D3
Input
26
PA0
Output
133
D3
Output
27
PA0
OEN
134
D2
Input
28
PHI
Output
135
D2
Output
29
PHI
OEN
136
D1
Input
30
SCL
Input
137
D1
Output
31
SCL
Output
138
D0
Input
32
SDA
Input
139
D0
Output
33
SDA
Output
140
D0
OEN
34
PB7
Input
141
CS3
Output
35
PB7
Output
142
CS2
Output
36
PB7
OEN
143
CS1
Output
37
PB6
Input
144
CS0
Output
38
PB6
Output
145
A23
Input
39
PB6
OEN
146
A23
Output
40
PB5
Input
147
A22
Input
41
PB5
Output
148
A22
Output
42
PB5
OEN
149
A21
Input
43
PB4
Input
150
PS019215-0910
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
262
Table 151. Pin to Boundary Scan Cell Mapping (Continued)
Pin
Direction
Scan Cell No
Pin
Direction
Scan Cell No
A21
Output
44
PB4
Output
151
A20
Input
45
PB4
OEN
152
A20
Output
46
PB3
Input
153
A19
Input
47
PB3
Output
154
A19
Output
48
PB3
OEN
155
A18
Input
49
PB2
Input
156
A18
Output
50
PB2
Output
157
A17
Input
51
PB2
OEN
158
A17
Output
52
PB1
Input
159
A16
Input
53
PB1
Output
160
A16
Output
54
PB1
OEN
161
A16
OEN
55
PB0
Input
162
A15
Input
56
PB0
Output
163
A15
Output
57
PB0
OEN
164
A14
Input
58
PC7
Input
165
A14
Output
59
PC7
Output
166
A13
Input
60
PC7
OEN
167
A13
Output
61
PC6
Input
168
A12
Input
62
PC6
Output
169
A12
Output
63
PC6
OEN
170
A11
Input
64
PC5
Input
171
A11
Output
65
PC5
Output
172
A10
Input
66
PC5
OEN
173
A10
Output
67
PC4
Input
174
A9
Input
68
PC4
Output
175
A9
Output
69
PC4
OEN
176
A8
Input
70
PC3
Input
177
A8
Output
71
PC3
Output
178
A8
OEN
72
PC3
OEN
179
PS019215-0910
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
263
Table 151. Pin to Boundary Scan Cell Mapping (Continued)
Pin
Direction
Scan Cell No
Pin
Direction
Scan Cell No
A7
Input
73
PC2
Input
180
A7
Output
74
PC2
Output
181
A6
Input
75
PC2
OEN
182
A6
Output
76
PC1
Input
183
A5
Input
77
PC1
Output
184
A5
Output
78
PC1
OEN
185
A4
Input
79
PC0
Input
186
A4
Output
80
PC0
Output
187
A3
Input
81
PC0
OEN
188
A3
Output
82
PD7
Input
189
A2
Input
83
PD7
Output
190
A2
Output
84
PD7
OEN
191
A1
Input
85
PD6
Input
192
A1
Output
86
PD6
Output
193
A0
Input
87
PD6
OEN
194
A0
Output
88
PD5
Input
195
A0
OEN
89
PD5
Output
196
WP
Input
90
PD5
OEN
197
MII_MDIO
Input
91
PD4
Input
198
MII_MDIO
Output
92
PD4
Output
199
MII_MDIO
OEN
93
PD4
OEN
200
MII_MDC
Output
94
PD3
Input
201
MII_RxD3
Input
95
PD3
Output
202
MII_RxD2
Input
96
PD3
OEN
203
MII_RxD1
Input
97
PD2
Input
204
MII_RxD0
Input
98
PD2
Output
205
MII_Rx_DV
Input
99
PD2
OEN
206
MII_Rx_CLK
Input
100
PD1
Input
207
MII_Rx_ER
Input
101
PD1
Output
208
PS019215-0910
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
264
Table 151. Pin to Boundary Scan Cell Mapping (Continued)
Pin
Direction
Scan Cell No
Pin
Direction
Scan Cell No
MII_Tx_ER
Output
102
PD1
OEN
209
MII_Tx_CLK
Input
103
PD0
Input
210
MII_Tx_EN
Output
104
PD0
Output
211
MII_TxD0
Output
105
PD0
OEN
212
MII_TxD1
Output
106
Notes
1. The address bits 0–7, 8–15, and 16–23 each share a single output enable. In this table, the output enables are
associated with the LSb that they control.
2. Direction on the data bus is controlled by a single output enable. It is associated in this table with D[0].
3. MREQ, IORQ, INSTRDN, RD, and WR share an output enable; it is associated in this table with WR.
Usage
Boundary scan functionality is utilized by issuing the appropriate Test Access Port (TAP)
instruction and shifting data accordingly. Both of these steps are accomplished using the
JTAG interface. To activate the TAP (see OCI Activation on page 258), the TCK pin must
be driven Low at least two CPU system clock cycles prior to the deassertion of the RESET
pin. Otherwise the OCI-JTAG features are disabled.
As per the IEEE 1149.1 specification, the boundary scan cells capture system I/O on the
rising edge of TCK during the CAPTURE_DR state. This captured data is shifted on the
rising edge of TCK while in the SHIFT_DR state. Pins and logic receive shifted data only
when enabled, and only on the falling edge of TCK during the UPDATE_DR state, after
shifting is completed.
For more information about eZ80F91 boundary scan support, refer to Using BSDL Files
with eZ80® and eZ80Acclaim!® Devices (AN0114).
Boundary Scan Instructions
The eZ80F91 device’s boundary scan architecture supports the following instructions:
•
•
•
•
•
PS019215-0910
BYPASS (required)
SAMPLE (required)
EXTEST (required)
PRELOAD (required)
IDCODE (optional)
On-Chip Instrumentation
eZ80F91 MCU
Product Specification
265
Phase-Locked Loop
Overview
The Phase-Locked-Loop (PLL) is a programmable frequency multiplier that satisfies the
equation SCLK (Hz) = N * FOSC(Hz). Figure 57 displays the PLL block diagram.
System Clock
(FOSC < SCLK < FOSC * N)
SCLK-MUX
PLL_CTL1[0] = PLL Enable
RTC_CLK
(1MHz < FOSC < 10MHz)
x2
x1
Oscillator
Charge
Pump
PFD
Lock
Detect
PLL_INT
VCO
PLL_CTL0[7:6]
Off-Chip
Loop Filter
CPLL1
RPLL
CPLL2
Div N
PLL_CTL0[3:2]
{PLL_DIV_H, PLL_DIV_L}
Figure 57. Phase-Locked Loop Block Diagram
PLL includes seven main blocks as listed below:
•
•
•
•
•
•
•
PS019215-0910
Phase Frequency Detector
Charge Pump
Voltage Controlled Oscillator
Loop Filter
Divider
MUX/CLK Sync
Lock Detect
Phase-Locked Loop
eZ80F91 MCU
Product Specification
266
Phase Frequency Detector
The Phase Frequency Detector (PFD) is a digital block. The two inputs are the reference
clock (XTAL oscillator; see On-Chip Oscillators on page 335) and the PLL divider output.
The two outputs drive the internal charge pump and represent the error (or difference)
between the falling edges of the PFD inputs.
Charge Pump
The Charge Pump is an analog block that is driven by two digital inputs from the PFD that
control its programmable current sources. The internal current source contains four
programmable values: 1.5 mA, 1 mA, 500 µA, and 100 µA. These values are selected by
PLL_CTRL1[7:6]. The selected current drive is sinked/sourced onto the loop-filter node
according to the error (or difference) between the falling edges of the PFD inputs. Ideally,
when the PLL is locked, there are no errors (error = 0) and no current is sourced/sinked
onto the loop-filter node.
Voltage Controlled Oscillator
The Voltage Controlled Oscillator (VCO) is an analog block that exhibits an output
frequency proportional to its input voltage. The VCO input is driven from the charge
pump and filtered via the off-chip loop filter.
Loop Filter
The Loop Filter comprises off-chip passive components (usually 1 resistor and 2
capacitors) that filter/integrate charge from the internal charge pump. The filtered node
also drives the VCO input, which creates a proportional frequency output. When PLL is
not used, the Loop Filter pin must not be connected.
Divider
The Divider is a digital, programmable downcounter. The divider input is driven by the
VCO. The divider output drives the PFD. The function of the Divider is to divide the
frequency of its input signal by a programmable factor N and supply the result in its
output.
MUX/CLK Sync
The MUX/CLK Sync is a digital, software-controllable multiplexer that selects between
PLL or the XTAL oscillator as the system clock (SCLK). A PLL source is selected only
after the PLL is locked (via the lock detect block) to allow glitch-free clock switching.
Lock Detect
The Lock Detect digital block analyzes the PFD output for a locked condition. The PLL
block of the eZ80F91 device is considered locked when the error (or difference) between
the reference clock and divided-down VCO is less than the minimum timing lock criteria
PS019215-0910
Phase-Locked Loop
eZ80F91 MCU
Product Specification
267
for the number of consecutive reference clock cycles. The lock criteria is selected in the
PLL Control Register, PLL_CTL0[LDS_CTL]. When the locked condition is met, this
block outputs a logic High signal (lock) that interrupts the CPU.
PLL Normal Operation
By default (after system reset) the PLL is disabled and SCLK = XTAL oscillator. Ensuring
proper loop filter, supply voltages and external oscillator are correctly configured, the PLL
is enabled. The SCLK/Timer cannot choose the PLL as its source until the PLL is locked,
as determined by the lock detect block. By forcing the PLL to be locked prior to enabling
the PLL as a SCLK/Timer source, it is assured to be stable and accurate.
Figure 58 displays the programming flow for normal PLL operation.
POR/System
Reset
Execute instructions with
SCLK = XTAL Oscillator
Program:
{PLL Divider}
PLL_DIV_L then PLL_DIV_H
{Charge Pump & Lock criteria}
PLL_CTL0
Enable:
{Interrupts & PLL}
PLL_CTL1
Upon Lock Interrupt:
Set SCLK MUX to PLL (PLL_CTL0)
Disable Lock Interrupt Mask
(PLL_CTL1)
Execute Application Code
Figure 58. Normal PLL Programming Flow
PS019215-0910
Phase-Locked Loop
eZ80F91 MCU
Product Specification
268
Power Requirement to the Phase-Locked Loop Function
Regardless of whether or not you chooses to use the PLL module block as a clock source
for the eZ80F91 device, the PLL_VDD (pin 87) must be connected to a VDD supply and
the PLL_VSS (pin 84) must be connected to a VSS supply for proper operation of the
eZ80F91 using any system clock source.
PLL Registers
PLL Divider Control Register—Low and High Bytes
This register is designed such that the 11 bit divider value is loaded into the divider module whenever the PLL_DIV_H register is written. Therefore, the procedure must be to
load the PLL_DIV_L register, followed by the PLL_DIV_H register, for the divider to
receive the appropriate value.
The divider is designed such that any divider value less than two is ignored; a value of two
is used in its place.
The LSB of PLL divider N is set via the corresponding bits in the PLL_DIV_L register.
See Table 152 and Table 153 on page 269.
Note:
The PLL divider register are written only when the PLL is disabled. A read-back of the
PLL Divider registers returns 0.
Table 152. PLL Divider Register—Low Bytes (PLL_DIV_L = 005Ch)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
1
0
CPU Access
W
W
W
W
W
W
W
W
Note: W = Write only.
Bit 
Position
[7:0]
PLL_DIV_L
PS019215-0910
Value
Description
00h–FFh These bits represent the Low byte of the 11 bit PLL divider
value. The complete PLL divider value is returned by
{PLL_DIV_H, PLL_DIV_L}.
Phase-Locked Loop
eZ80F91 MCU
Product Specification
269
Table 153. PLL Divider Register—High Bytes (PLL_DIV_H = 005Dh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
W
W
W
W
W
W
W
W
Note: R = Read only; R/W = Read/Write.
Bit 
Position
Value
Description
[7:3]
00h
Reserved
[2:0]
PLL_DIV_H
0h–7h
These bits represent the High byte of the 11 bit PLL divider
value. The complete PLL divider value is returned by
{PLL_DIV_H, PLL_DIV_L}.
PLL Control Register 0
The charge pump program, lock detect sensitivity, and system clock source selections are
set using this register. A brief description of each of these PLL Control Register 0
attributes is listed below, and further listed in Table 154.
Charge Pump Program (CHRP_CTL)—Selects one of four values of charge pump
current.
Lock Detect Sensitivity (LDS_CTL)—Determines the lock criteria for the PLL.
System Clock Source (CLK_MUX)—Selects the system clock source from a choice of
the external crystal oscillator (XTAL), PLL, or Real-Time Clock crystal oscillator.
Table 154. PLL Control Register 0 (PLL_CTL0 = 005Eh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R
R
R/W
R/W
R/W
R/W
CPU Access
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
[7:6]
CHRP_CTL1
PS019215-0910
Value Description
00
Charge pump current = 100 µA
01
Charge pump current = 500 µA
10
Charge pump current = 1.0 mA
11
Charge pump current = 1.5 mA
Phase-Locked Loop
eZ80F91 MCU
Product Specification
270
Bit 
Position
Value Description
[5:4]
00
Reserved
[3:2]
LDS_CTL1
00
Lock criteria—8 consecutive cycles of 20 ns
01
Lock criteria—16 consecutive cycles of 20 ns
10
Lock criteria—8 consecutive cycles of 400 ns
11
Lock criteria—16 consecutive cycles of 400 ns
00
System clock source is the external crystal oscillator
01
System clock source is the PLL2
10
System clock source is the Real-Time Clock crystal oscillator
11
Reserved (previous select is preserved)
[1:0]
CLK_MUX
Notes
1. Bits are programmed only when the PLL is disabled. The PLL is disabled when PLL_CTL1 bit
0 is equal to 0.
2. PLL cannot be selected when disabled or out of lock.
PLL Control Register 1
The PLL is enabled using this register. PLL lock-detect status, the PLL interrupt signals
and the PLL interrupt enables are accessed via this register. A brief description of each of
these PLL Control Register 1 attributes is listed below, and further listed in Table 155 on
page 271.
Lock Status (LCK_STATUS)—The current lock bit out of the PLL is synchronized and
read via this bit.
Interrupt Lock (INT_LOCK)—This signal feeds the interrupt line out of the CLKGEN
module and indicates that a rising edge on the lock signal out of the PLL has been
observed.
Interrupt Unlock (INT_UNLOCK)—This signal feeds the interrupt line out of the clkgen
module and indicates that a falling edge on the lock signal out of the PLL has been
observed.
Interrupt Lock Enable (INT_LOCK_EN)—This signal enables the interrupt lock bit.
Interrupt Unlock Enable (INT_UNLOCK_EN)—This signal enables the interrupt unlock
bit.
PLL Enable (PLL_ENABLE)—Enables/disables the PLL.
PS019215-0910
Phase-Locked Loop
eZ80F91 MCU
Product Specification
271
.Table
155. PLL Control Register 1 (PLL_CTL1 = 005Fh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value Description
[7:6]
00
Reserved.
5
LCK_STATUS
0
PLL is currently out of lock.
1
PLL is currently locked.
4
INT_LOCK
0
Lock signal from PLL has not risen since last time register was
read.
1
Interrupt generated when PLL enters LOCK mode. Held until
register is read.
0
Lock signal from PLL has not fallen since last time register was
read.
1
Interrupt generated when PLL goes out of lock. Held until
register is read.
3
INT_UNLOCK
2
0
INT_LOCK_EN
1
1
0
INT_UNLOCK_
EN
1
0
PLL_ENABLE
Interrupt generation for PLL locked condition (Bit 4) is disabled.
Interrupt generation for PLL locked condition is enabled.
Interrupt generation for PLL unlocked condition (Bit 3) is
disabled.
Interrupt generation for PLL unlocked condition is enabled.
0
PLL is disabled.1
1
PLL is enabled.
Note
1. PLL cannot be disabled if the CLK_MUX bit of PLL_CTL0[1:0] is set to 01, because the PLL is
selected as the clock source.
PS019215-0910
Phase-Locked Loop
eZ80F91 MCU
Product Specification
272
PLL Characteristics
The operating and testing characteristics for the PLL are listed in Table 156.
Note:
Not all conditions are tested in production test. The values in Table 156 are for design and
characterization only.
Table 156. PLL Characteristics
Symbol
Parameter
Test Condition
IoHCP_OUT
High level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD < 3.6
0.6 < PD_OUT < VDD – 0.6
PLL_CTL0[7:6] = 11
–0.86 –1.50 –2.13
mA
IoLCP_OUT
Low level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT < VDD – 0.6
PLL_CTL0[7:6] = 11
0.86
1.50
2.13
mA
IoHCP_OUT
High level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT < VDD – 0.6
PLL_CTL0[7:6] = 10
–0.42
–1.0
–1.42
mA
IoLCP_OUT
Low level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT <VDD – 0.6
PLL_CTL0[7:6] = 10
0.42
1.0
1.42
mA
IoHCP_OUT
High level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT <VDD – 0.6
PLL_CTL0[7:6] = 01
–210
–500
–710
µA
IoLCP_OUT
Low level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT <VDD – 0.6
PLL_CTL0[7:6] = 01
210
500
710
µA
IoHCP_OUT
High level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT <VDD – 0.6
PLL_CTL0[7:6] = 00
–42
–100
–142
µA
IoLCP_OUT
Low level output current for
CP_OUT pin (programmed
value ± 42%)
3.0 < VDD <3.6
0.6 < PD_OUT <VDD – 0.6
PLL_CTL0[7:6] = 00
42
100
142
µA
Match
IOHCP_OUT–IOLCP_OUT 
current match
3.0 < VDD <3.6
0.6 < CP_OUT <VDD – 0.6
PLL_CTL0[7:6] = XX
–15
+15
%
ILCP_OUT
Tristate leakage on CP_OUT CP_OUT tristated
output pin
–1
1
µA
Fosc
Crystal oscillator frequency
1M
10 M
Hz
PS019215-0910
PLL_CTL0[5:4] = 01
Min
Typ
Max
Units
Phase-Locked Loop
eZ80F91 MCU
Product Specification
273
Table 156. PLL Characteristics (Continued)
Symbol
Parameter
Test Condition
Fvco
VCO frequency
Recommended operating
conditions
Gvco
VCO Gain
Recommended operating
conditions
36
D1
SCLK Duty Cycle from PLL or Recommended operating
XTALOSC source
conditions
45
T1A
PLL Clock Jitter
FVCO = 50 MHz. XTALOSC
= 10 MHz
Lock2
PLL Lock-Time
FVCO = 50 MHz. XTALOSC
= 3.579 MHz
Cpll1 = 220 pF, Rpll = 499 ¾,
Cpll2 = 0.056 µF
IoH1
(XTL)
High-level Output Current for
XTAL2 pin
VoH = VDD–0.4 V
PLL_CTL0[5:4] = 01
–0.3
mA
IoL1
(XTL)
Low-level Output Current for
XTAL2 pin
VoL = 0.4 V
PLL_CTL0[5:4] = 01
0.6
mA
IoH2
(XTL)
High-level Output Current for
XTAL2 pin
VoH = VDD–0.4 V
PLL_CTL0[5:4] = 11
mA
IoL2
(XTL)
Low-level Output Current for
XTAL2 pin
VoL = 0.4 V
PLL_CTL0[5:4] = 11
mA
VPP3M 
(XTL)
Peak-to-peak voltage under
oscillator conditions for
XTAL2 pin
FOSC = 3.579 MHz
Cx1 = 10 pF
Cx2 = 10 pF
V
VPP10M 
(XTL)
Peak-to-peak voltage under
oscillator conditions for
XTAL2 pin
FOSC = 10 MHz
Cx1 = 10 pF
Cx2 = 10 pF
V
Cxtal1
(package
type)
Capacitance measured from
XTAL1 pin to GND
T = 25 ºC
pF
Cxtal2
(package
type)
Capacitance measured from
XTAL2 pin to GND
T = 25 ºC
pF
Cloop
(package
type)
Capacitance measured from
loop filter pin to GND
T = 25 ºC
pF
PS019215-0910
Min
Typ
Max
50
Units
MHz
120
MHz/
V
50
55
%
350
500
ps
s
Phase-Locked Loop
eZ80F91 MCU
Product Specification
274
PS019215-0910
Phase-Locked Loop
eZ80F91 MCU
Product Specification
275
eZ80® CPU Instruction Set
Table 157 through Table 166 on page 278 lists the CPU instructions available for use with
the eZ80F91 device. The instructions are grouped by class. For more information, refer to
eZ80® CPU User Manual (UM0077).
Table 157. Arithmetic Instructions
Mnemonic
Instruction
ADC
Add with Carry
ADD
Add without Carry
CP
Compare with Accumulator
DAA
Decimal Adjust Accumulator
DEC
Decrement
INC
Increment
MLT
Multiply
NEG
Negate Accumulator
SBC
Subtract with Carry
SUB
Subtract without Carry
Table 158. Bit Manipulation Instructions
Mnemonic
Instruction
BIT
Bit Test
RES
Reset Bit
SET
Set Bit
Table 159. Block Transfer and Compare Instructions
PS019215-0910
Mnemonic
Instruction
CPD (CPDR)
Compare and Decrement (with Repeat)
CPI (CPIR)
Compare and Increment (with Repeat)
LDD (LDDR)
Load and Decrement (with Repeat)
LDI (LDIR)
Load and Increment (with Repeat)
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
276
Table 160. Exchange Instructions
Mnemonic
Instruction
EX
Exchange registers
EXX
Exchange CPU Multibyte register banks
Table 161. Input/Output Instructions
PS019215-0910
Mnemonic
Instruction
IN
Input from I/O
IN0
Input from I/O on Page 0
IND (INDR)
Input from I/O and Decrement (with Repeat)
INDRX
Input from I/O and Decrement Memory Address with Stationary
I/O Address
IND2 (IND2R)
Input from I/O and Decrement (with Repeat)
INDM (INDMR)
Input from I/O and Decrement (with Repeat)
INI (INIR)
Input from I/O and Increment (with Repeat)
INIRX
Input from I/O and Increment Memory Address with Stationary
I/O Address
INI2 (INI2R)
Input from I/O and Increment (with Repeat)
INIM (INIMR)
Input from I/O and Increment (with Repeat)
OTDM (OTDMR)
Output to I/O and Decrement (with Repeat)
OTDRX
Output to I/O and Decrement Memory Address with Stationary
I/O Address
OTIM (OTIMR)
Output to I/O and Increment (with Repeat)
OTIRX
Output to I/O and Increment Memory Address with Stationary
I/O Address
OUT
Output to I/O
OUT0
Output to I/0 on Page 0
OUTD (OTDR)
Output to I/O and Decrement (with Repeat)
OUTD2 (OTD2R)
Output to I/O and Decrement (with Repeat)
OUTI (OTIR)
Output to I/O and Increment (with Repeat)
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
277
Table 161. Input/Output Instructions (Continued)
Mnemonic
Instruction
OUTI2 (OTI2R)
Output to I/O and Increment (with Repeat)
TSTIO
Test I/O
Table 162. Load Instructions
Mnemonic
Instruction
LD
Load
LEA
Load Effective Address
PEA
Push Effective Address
POP
Pop
PUSH
Push
Table 163. Logical Instructions
Mnemonic
Instruction
AND
Logical AND
CPL
Complement Accumulator
OR
Logical OR
TST
Test Accumulator
XOR
Logical Exclusive OR
Table 164. Processor Control Instructions
PS019215-0910
Mnemonic
Instruction
CCF
Complement Carry Flag
DI
Disable Interrupts
EI
Enable Interrupts
HALT
Halt
IM
Interrupt Mode
NOP
No Operation
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
278
Table 164. Processor Control Instructions (Continued)
Mnemonic
Instruction
RSMIX
Reset Mixed-Memory Mode Flag
SCF
Set Carry Flag
SLP
Sleep
STMIX
Set Mixed-Memory Mode Flag
Table 165. Program Control Instructions
Mnemonic
Instruction
CALL
Call Subroutine
CALL cc
Conditional Call Subroutine
DJNZ
Decrement and Jump if Nonzero
JP
Jump
JP cc
Conditional Jump
JR
Jump Relative
JR cc
Conditional Jump Relative
RET
Return
RET cc
Conditional Return
RETI
Return from Interrupt
RETN
Return from Nonmaskable interrupt
RST
Restart
Table 166. Rotate and Shift Instructions
PS019215-0910
Mnemonic
Instruction
RL
Rotate Left
RLA
Rotate Left–Accumulator
RLC
Rotate Left Circular
RLCA
Rotate Left Circular–Accumulator
RLD
Rotate Left Decimal
RR
Rotate Right
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
279
Table 166. Rotate and Shift Instructions (Continued)
PS019215-0910
Mnemonic
Instruction
RRA
Rotate Right–Accumulator
RRC
Rotate Right Circular
RRCA
Rotate Right Circular–Accumulator
RRD
Rotate Right Decimal
SLA
Shift Left Arithmetic
SRA
Shift Right Arithmetic
SRL
Shift Right Logical
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
280
Opcode Map
Table 167 through Table 173 on page 286 list the hex values for each of the eZ80® instructions.
Table 167. Opcode Map—First Opcode
Legend
Lower Opcode Nibble
Upper
Opcode
Nibble
4
AND
A
A,H
First Operand
Upper Nibble (Hex)
0
NOP
1
0
LD
BC,
Mmn
1 DJNZ
LD
d
DE,
Mmn
2
JR
LD
NZ,d
HL,
Mmn
3
JR
LD
NC,d
SP,
Mmn
4 .SIS
LD
suffix
B,C
5
LD
LD
D,B
D,C
6
LD
LD
H,B
H,C
7
LD
LD
(HL),B (HL),C
8 ADD
ADD
A,B
A,C
9 SUB
SUB
A,B
A,C
A AND
AND
A,B
A,C
B
OR
OR
A,B
A,C
C RET
POP
NZ
BC
D
E
F
Mnemonic
Second Operand
2
LD
(BC),A
3
INC
BC
4
INC
B
5
DEC
B
Lower Nibble (Hex)
6
7
8
9
A
LD
RLCA
EX
ADD
LD
B,n
AF,AF’ HL,BC A,(BC)
B
DEC
BC
C
INC
C
D
DEC
C
E
LD
C,n
F
RRCA
LD
(DE),A
INC
DE
INC
D
DEC
D
LD
D,n
RLA
JR
d
ADD
LD
HL,DE A,(DE)
DEC
DE
INC
E
DEC
E
LD
E,n
RRA
LD
H,n
DAA
JR
Z,d
ADD
HL,HL
DEC
HL
INC
L
DEC
L
LD
L,n
CPL
LD
(HL),n
SCF
JR
CF,d
DEC
SP
INC
A
DEC
A
LD
A,n
CCF
LD
B,(HL)
LD
D,(HL)
LD
H,(HL)
HALT
ADD
A,(HL)
SUB
A,(HL)
AND
A,(HL)
OR
A,(HL)
ADD
A,n
LD
B,A
LD
D,A
LD
H,A
LD
(HL),A
ADD
A,A
SUB
A,A
AND
A,A
OR
A,A
RST
00h
LD
C,B
LD
E,B
LD
L,B
LD
A,B
ADC
A,B
SBC
A,B
XOR
A,B
CP
A,B
RET
Z
LD
C,E
.LIL
suffix
LD
L,E
LD
A,E
ADC
A,E
SBC
A,E
XOR
A,E
CP
A,E
LD
C,H
LD
E,H
LD
L,H
LD
A,H
ADC
A,H
SBC
A,H
XOR
A,H
CP
A,H
CALL
Z,
Mmn
LD
C,L
LD
E,L
LD
L,L
LD
A,L
ADC
A,L
SBC
A,L
XOR
A,L
CP
A,L
CALL
Mmn
See
INC
INC
DEC
LD
(Mmn),
HL
H
H
HL
LD
INC
INC
DEC
(HL)
(Mmn), SP
(HL)
A
LD
LD
LD
LD
B,D
B,E
B,H
B,L
.SIL
LD
LD
LD
suffix
D,E
D,H
D,L
LD
LD
LD
LD
H,D
H,E
H,H
H,L
LD
LD
LD
LD
(HL),D (HL),E (HL),H (HL),L
ADD
ADD
ADD
ADD
A,D
A,E
A,H
A,L
SUB
SUB
SUB
SUB
A,D
A,E
A,H
A,L
AND
AND
AND
AND
A,D
A,E
A,H
A,L
OR
OR
OR
OR
A,D
A,E
A,H
A,L
JP
JP
CALL PUSH
NZ,
Mmn
NZ,
BC
Mmn
Mmn
RET
NC
POP
DE
JP
NC,
Mmn
CALL
NC,
Mmn
PUSH
DE
SUB
A,n
RST
10h
RET
CF
EXX
RET
PO
POP
HL
JP
EX
CALL
PO, (SP),HL PO,
Mmn
Mmn
PUSH
HL
AND
A,n
RST
20h
RET
PE
RET
P
POP
AF
JP
P,
Mmn
PUSH
AF
OR
A,n
RST
30h
RET
M
PS019215-0910
OUT
(n),A
LD
HL,
(Mmn)
ADD
LD
HL,SP
A,
(Mmn)
.LIS
LD
suffix
C,D
LD
LD
E,C
E,D
LD
LD
L,C
L,D
LD
LD
A,C
A,D
ADC
ADC
A,C
A,D
SBC
SBC
A,C
A,D
XOR
XOR
A,C
A,D
CP
CP
A,C
A,D
RET
JP
Z,
Mmn
DI
CALL
P,
Mmn
See
Table
168
JP
CF,
Mmn
IN
A,(n)
CALL
CF,
Mmn
JP
(HL)
JP
PE,
Mmn
EX
DE,HL
CALL
PE,
Mmn
LD
SP,HL
JP
M,
Mmn
EI
CALL
M,
Mmn
Table
169
See
Table
170
See
Table
171
LD
LD
C,(HL) C,A
LD
LD
E,(HL) E,A
LD
LD
L,(HL) L,A
LD
LD
A,(HL) A,A
ADC ADC
A,(HL) A,A
SBC SBC
A,(HL) A,A
XOR XOR
A,(HL) A,A
CP
CP
A,(HL) A,A
ADC RST
A,n
08h
SBC
A,n
RST
18h
XOR
A,n
RST
28h
CP
A,n
RST
38h
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
281
Table 167. Opcode Map—First Opcode (Continued)
Note: n = 8-bit data; Mmn = 16- or 24-bit addr or data; d = 8-bit two’s-complement displacement.
Table 168. Opcode Map—Second Opcode after 0CBh
Legend
Lower Nibble of 2nd Opcode
Upper
Nibble
of Second
Opcode
4
A RES
4,H
First Operand
Mnemonic
Second Operand
Lower Nibble (Hex)
0
1
2
0
RLC
B
RL
B
SLA
B
1
RLC
C
RL
C
SLA
C
2
RLC
D
RL
D
SLA
D
3
RLC
E
RL
E
SLA
E
4
RLC
H
RL
H
SLA
H
5
RLC
L
RL
L
SLA
L
6
RLC
(HL)
RL
(HL)
SLA
(HL)
7
RLC
A
RL
A
SLA
A
BIT
0,B
BIT
2,B
BIT
4,B
BIT
6,B
RES
0,B
RES
2,B
RES
4,B
RES
6,B
SET
0,B
SET
2,B
SET
4,B
SET
6,B
BIT
0,C
BIT
2,C
BIT
4,C
BIT
6,C
RES
0,C
RES
2,C
RES
4,C
RES
6,C
SET
0,C
SET
2,C
SET
4,C
SET
6,C
BIT
0,D
BIT
2,D
BIT
4,D
BIT
6,D
RES
0,D
RES
2,D
RES
4,D
RES
6,D
SET
0,D
SET
2,D
SET
4,D
SET
6,D
BIT
0,E
BIT
2,E
BIT
4,E
BIT
6,E
RES
0,E
RES
2,E
RES
4,E
RES
6,E
SET
0,E
SET
2,E
SET
4,E
SET
6,E
BIT
0,H
BIT
2,H
BIT
4,H
BIT
6,H
RES
0,H
RES
2,H
RES
4,H
RES
6,H
SET
0,H
SET
2,H
SET
4,H
SET
6,H
BIT
0,L
BIT
2,L
BIT
4,L
BIT
6,L
RES
0,L
RES
2,L
RES
4,L
RES
6,L
SET
0,L
SET
2,L
SET
4,L
SET
6,L
BIT
0,(HL)
BIT
2,(HL)
BIT
4,(HL)
BIT
6,(HL)
RES
0,(HL)
RES
2,(HL)
RES
4,(HL)
RES
6,(HL)
SET
0,(HL)
SET
2,(HL)
SET
4,(HL)
SET
6,(HL)
BIT
0,A
BIT
2,A
BIT
4,A
BIT
6,A
RES
0,A
RES
2,A
RES
4,A
RES
6,A
SET
0,A
SET
2,A
SET
4,A
SET
6,A
3
4
5
Upper Nibble (Hex)
6
7
8
9
A
B
C
D
E
F
8
RRC
B
RR
B
SRA
B
SRL
B
BIT
1,B
BIT
3,B
BIT
5,B
BIT
7,B
RES
1,B
RES
3,B
RES
5,B
RES
7,B
SET
1,B
SET
3,B
SET
5,B
SET
7,B
9
RRC
C
RR
C
SRA
C
SRL
C
BIT
1,C
BIT
3,C
BIT
5,C
BIT
7,C
RES
1,C
RES
3,C
RES
5,C
RES
7,C
SET
1,C
SET
3,C
SET
5,C
SET
7,C
A
RRC
D
RR
D
SRA
D
SRL
D
BIT
1,D
BIT
3,D
BIT
5,D
BIT
7,D
RES
1,D
RES
3,D
RES
5,D
RES
7,D
SET
1,D
SET
3,D
SET
5,D
SET
7,D
B
RRC
E
RR
E
SRA
E
SRL
E
BIT
1,E
BIT
3,E
BIT
5,E
BIT
7,E
RES
1,E
RES
3,E
RES
5,E
RES
7,E
SET
1,E
SET
3,E
SET
5,E
SET
7,E
C
RRC
H
RR
H
SRA
H
SRL
H
BIT
1,H
BIT
3,H
BIT
5,H
BIT
7,H
RES
1,H
RES
3,H
RES
5,H
RES
7,H
SET
1,H
SET
3,H
SET
5,H
SET
7,H
D
RRC
L
RR
L
SRA
L
SRL
L
BIT
1,L
BIT
3,L
BIT
5,L
BIT
7,L
RES
1,L
RES
3,L
RES
5,L
RES
7,L
SET
1,L
SET
3,L
SET
5,L
SET
7,L
E
RRC
(HL)
RR
(HL)
SRA
(HL)
SRL
(HL)
BIT
1,(HL)
BIT
3,(HL)
BIT
5,(HL)
BIT
7,(HL)
RES
1,(HL)
RES
3,(HL)
RES
5,(HL)
RES
7,(HL)
SET
1,(HL)
SET
3,(HL)
SET
5,(HL)
SET
7,(HL)
F
RRC
A
RR
A
SRA
A
SRL
A
BIT
1,A
BIT
3,A
BIT
5,A
BIT
7,A
RES
1,A
RES
3,A
RES
5,A
RES
7,A
SET
1,A
SET
3,A
SET
5,A
SET
7,A
Note: n = 8-bit data; Mmn = 16- or 24-bit addr or data; d = 8-bit two’s-complement displacement.
PS019215-0910
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
282
Table 169. Opcode Map—Second Opcode After 0DDh
Legend
Lower Nibble of 2nd Opcode
Upper
Nibble
of Second
Opcode
9
F LD
SP,IX
Mnemonic
Second Operand
First Operand
Lower Nibble (Hex)
0
1
2
3
4
5
6
0
1
2
3
4
Upper Nibble (Hex)
5
6
7
8
9
A
B
LD
LD
IX,
(Mmn),
Mmn
IX
LD IY,
(IX+d)
INC
IX
7
LD BC,
(IX+d)
8
9
ADD
IX,BC
LD DE,
(IX+d)
ADD
IX,DE
INC
IXH
DEC
IXH
LD
LD HL,
IXH,n (IX+d)
ADD
IX,IX
INC
(IX+d)
DEC
(IX+d)
LD (IX LD IX,
+d),n (IX+d)
ADD
IX,SP
LD
LD
B,IXH B,IXL
LD
LD
D,IXH D,IXL
LD
LD
LD
LD
LD
LD
IXH,B IXH,C IXH,D IXH,E IXH,IXH IXH,IXL
LD
LD
LD
LD
LD
LD
(IX+d),B (IX+d),C (IX+d),D (IX+d),E (IX+d),H (IX+d),L
ADD
ADD
A,IXH A,IXL
SUB
SUB
A,IXH A,IXL
AND
AND
A,IXH A,IXL
OR
OR
A,IXH A,IXL
LD B,
(IX+d)
LD D,
(IX+d)
LD H,
(IX+d)
LD
LD
IXH,A IXL,B
LD
(IX+d),A
LD
IXL,C
ADD A,
(IX+d)
SUB A,
(IX+d)
AND A,
(IX+d)
OR A,
(IX+d)
A
B
C
D
LD
IX,
(Mmn)
DEC
IX
INC
IXL
DEC
IXL
LD
IXL,D
LD
C,IXH
LD
E,IXH
LD
LD
IXL,E IXL,IXH
LD
A,IXH
ADC
A,IXH
SBC
A,IXH
XOR
A,IXH
CP
A,IXH
LD
C,IXL
LD
E,IXL
LD
IXL,IXL
LD
A,IXL
ADC
A,IXL
SBC
A,IXL
XOR
A,IXL
CP
A,IXL
E
F
LD
(IX+d),
BC
LD
(IX+d),
DE
LD
LD
IXL,n (IX+d),
HL
LD
LD
(IX+d), (IX+d),
IY
IX
LD C,
(IX+d)
LD E,
(IX+d)
LD L,
LD
(IX+d) IXL,A
LD A,
(IX+d)
ADC A,
(IX+d)
SBC A,
(IX+d)
XOR A,
(IX+d)
CP A,
(IX+d)
Table
172
C
D
E
POP
IX
F
EX
(SP),IX
PUSH
IX
JP
(IX)
LD
SP,IX
Note: n = 8-bit data; Mmn = 16- or 24-bit addr or data; d = 8-bit two’s-complement displacement.
PS019215-0910
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
283
Table 170. Opcode Map—Second Opcode After 0EDh
Legend
Lower Nibble of 2nd Opcode
Upper
Nibble
of Second
Opcode
2
4 SBC
HL,BC
First Operand
Mnemonic
Second Operand
Lower Nibble (Hex)
0
IN0
B,(n)
1
OUT0
(n),B
1
IN0
D,(n)
OUT0
(n),D
2
IN0
H,(n)
OUT0
(n),H
0
4
TST
A,B
7
8
LD BC, IN0
(HL)
C,(n)
9
OUT0
(n),C
TST
A,D
LD DE,
(HL)
IN0
E,(n)
OUT0
(n),E
TST
A,E
TST
A,H
LD HL,
(HL)
IN0
L,(n)
OUT0
(n),L
TST
A,L
LD IX,
(HL)
IN0
A,(n)
OUT0
(n),A
TST
A,A
3
LD IY, LEA IX LEA IY TST
(HL)
,IX+d ,IY+d A,(HL)
4
IN
OUT
SBC
LD
NEG
B,(BC) (BC),B HL,BC (Mmn),
BC
IN
OUT
SBC
LD LEA IX,
D,(BC) (BC),D HL,DE (Mmn), IY+d
DE
IBN
OUT
SBC
LD
TST
H,(C) (BC),H HL,HL (Mmn), A,n
HL
SBC
LD
TSTIO
HL,SP (Mmn),
n
SP
INIM OTIM
INI2
5
Upper Nibble (Hex)
2
3
LEA
LEA
BC,
BC,
IX+d
IY+d
LEA
LEA
DE,
DE,
IX+d
IY+d
LEA HL LEA HL
,IX+d ,IY+d
6
7
8
9
5
6
RETN
IM 0
LD
I,A
IN
C,(C)
OUT
(C),C
ADC
HL,BC
LEA IY,
IX+d
IM 1
LD
A,I
IN
E,(C)
OUT
(C),E
ADC
HL,DE
PEA
IX+d
PEA
IY+d
RRD
IN
L,(C)
OUT
(C),L
ADC
HL,HL
IN
A,(C)
OUT
(C),A
ADC
HL,SP
SLP
INDM
INIMR OTIMR INI2R
A
LDI
CPI
INI
OUTI
OUTI2
B
LDIR
CPIR
INIR
OTIR
OTI2R
C
INIRX OTIRX
D
A
B
LD
BC,
(Mmn)
LD
DE,
(Mmn)
LD
HL,
(Mmn)
LD
SP,
(Mmn)
OTDM
C
TST
A,C
MLT
BC
D
E
LD
(HL),IY
RETI
MLT
DE
MLT
HL
MLT
SP
LD
MB,A
F
LD
(HL),
BC
LD(HL),
DE
LD
(HL),
HL
LD
(HL),
IX
LD
R,A
IM 2
LD
A,R
LD
A,MB
RLD
STMIX RSMIX
IND2
INDMR OTDMR IND2R
LDD
CPD
LDDR CPDR
LD
I,HL
LD
HL,I
IND
OUTD OUTD2
INDR
OTDR OTD2R
INDRX OTDRX
E
F
Note: n = 8-bit data; Mmn = 16- or 24-bit addr or data; d = 8-bit two’s-complement displacement.
PS019215-0910
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
284
Table 171. Opcode Map—Second Opcode After 0FDh
Legend
Lower Nibble of 2nd Opcode
Upper
Nibble
of Second
Opcode
9
F LD
SP,IY
Mnemonic
First Operand
Second Operand
Lower Nibble (Hex)
0
1
2
3
4
5
INC
IY
INC
IYH
DEC
IYH
0
1
2
3
4
Upper Nibble (Hex)
5
6
7
8
9
A
B
LD
LD
IY,Mmn (Mmn),I
Y
LD IX,
(IY+d)
INC
DEC
(IY+d) (IY+d)
LD
LD
B,IYH B,IYL
LD
LD
D,IYH D,IYL
LD
LD
LD
LD
LD
LD
IYH,B IYH,C IYH,D IYH,E IYH,IYH IYH,IYL
LD (IY LD (IY LD (IY LD (IY LD (IY LD (IY
+d),B +d),C +d),D +d),E +d),H +d),L
ADD
ADD
A,IYH A,IYL
SUB
SUB
A,IYH A,IYL
AND
AND
A,IYH A,IYL
OR
OR
A,IYH A,IYL
6
7
LD BC,
(IY+d)
LD DE,
(IY+d)
LD
LD HL,
IYH,n (IY+d)
LD (IY LD IY,
+d),n (IY+d)
LD B,
(IY+d)
LD D,
(IY+d)
LD H,
LD
(IY+d) IYH,A
LD (IY
+d),A
ADD A,
(IY+d)
SUB A,
(IY+d)
AND A,
(IY+d)
OR A,
(IY+d)
8
9
ADD
IY,BC
ADD
IY,DE
ADD
IY,IY
A
B
C
D
LD
IY,
(Mmn)
DEC
IY
INC
IYL
DEC
IYL
ADD
IY,SP
LD
IYL,B
LD
IYL,C
LD
IYL,D
LD
C,IYH
LD
E,IYH
LD
LD
IYL,E IYL,IYH
LD
A,IYH
ADC
A,IYH
SBC
A,IYH
XOR
A,IYH
CP
A,IYH
LD
C,IYL
LD
E,IYL
LD
IYL,IYL
LD
A,IYL
ADC
A,IYL
SBC
A,IYL
XOR
A,IYL
CP
A,IYL
E
F
LD (IY
+d),BC
LD (IY
+d),DE
LD
LD (IY
IYL,n +d),HL
LD (IY LD (IY
+d),IX +d),IY
LD C,
(IY+d)
LD E,
(IY+d)
LD L,
LD
(IY+d) IYL,A
LD A,
(IY+d)
ADC A,
(IY+d)
SBC A,
(IY+d)
XOR A,
(IY+d)
CP A,
(IY+d)
Table
173
C
D
E
POP
IY
F
EX
(SP),IY
PUSH
IY
JP
(IY)
LD
SP,IY
Note: n = 8-bit data; Mmn = 16- or 24-bit addr or data; d = 8-bit two’s-complement displacement.
PS019215-0910
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
285
Table 172. Opcode Map—Fourth Byte After 0DDh, 0CBh, and dd
Legend
Lower Nibble of 4th Byte
Upper
Nibble
of Fourth
Byte
6
BIT
4 0,(IX+d)
First Operand
Mnemonic
Second Operand
Lower Nibble (Hex)
0
1
0
1
2
2
3
4
5
6
RLC
(IX+d)
RL
(IX+d)
SLA
(IX+d)
7
3
4
BIT 0,
(IX+d)
BIT 2,
(IX+d)
BIT 4,
(IX+d)
BIT 6,
(IX+d)
RES 0,
(IX+d)
RES 2,
(IX+d)
RES 4,
(IX+d)
RES 6,
(IX+d)
SET 0,
(IX+d)
SET 2,
(IX+d)
SET 4,
(IX+d)
SET 6,
(IX+d)
Upper Nibble (Hex)
5
6
7
8
9
A
B
C
D
E
F
8
9
A
B
C
D
E
RRC
(IX+d)
RR
(IX+d)
SRA
(IX+d)
SRL
(IX+d)
BIT 1,
(IX+d)
BIT 3,
(IX+d)
BIT 5,
(IX+d)
BIT 7,
(IX+d)
RES 1,
(IX+d)
RES 3,
(IX+d)
RES 5,
(IX+d)
RES 7,
(IX+d)
SET 1,
(IX+d)
SET 3,
(IX+d)
SET 5,
(IX+d)
SET 7,
(IX+d)
F
Note: d = 8-bit two’s-complement displacement
PS019215-0910
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
286
Table 173. Opcode Map—Fourth Byte After 0FDh, 0CBh, and dd
Legend
Lower Nibble of 4th Byte
Upper
Nibble
of Fourth
Byte
4
6
BIT
0,(IY+d)
First Operand
Mnemonic
Second Operand
Lower Nibble (Hex)
0
1
0
1
2
2
3
4
5
6
RLC
(IY+d)
RL
(IY+d)
SLA
(IY+d)
3
4
BIT 0,
(IY+d)
BIT 2,
(IY+d)
BIT 4,
(IY+d)
BIT 6,
(IY+d)
RES 0,
(IY+d)
RES 2,
(IY+d)
RES 4,
(IY+d)
RES 6,
(IY+d)
SET 0,
(IY+d)
SET 2,
(IY+d)
SET 4,
(IY+d)
SET 6,
(IY+d)
Upper Nibble (Hex)
5
6
7
8
9
A
B
C
D
E
F
7
8
9
A
B
C
D
E
RRC
(IY+d)
RR
(IY+d)
SRA
(IY+d)
SRL
(IY+d)
BIT 1,
(IY+d)
BIT 3,
(IY+d)
BIT 5,
(IY+d)
BIT 7,
(IY+d)
RES 1,
(IY+d)
RES 3,
(IY+d)
RES 5,
(IY+d)
RES 7,
(IY+d)
SET 1,
(IY+d)
SET 3,
(IY+d)
SET 5,
(IY+d)
SET 7,
(IY+d)
F
Note: d = 8-bit two’s-complement displacement
PS019215-0910
eZ80® CPU Instruction Set
eZ80F91 MCU
Product Specification
287
Ethernet Media Access Controller
The Ethernet Media Access Controller (EMAC) is a full-function 10/100 Mbps media
access control module with a Media-Independent Interface (MII). When communicating
with an external PHY device, the eZ80F91 MCU uses the MII to gain access to the
Ethernet network.
Figure 59 displays the EMAC block diagram.
MDIO
MDC
Memory
RxD
RxCLK
RxDV
RxER
Arbiter
MII Interface
TxFIFO
Media Access Controller
TxD
TxCLK
TxER
TxEN
COL
CRS
TxDMA
RxD
RxD/CTRL
RxFIFO
Accept
CTRL
RxDMA
Reject
Figure 59. EMAC Block Diagram
Note:
For additional information about the Ethernet protocol and using it with the eZ80F91
MCU, refer to the IEEE 802.3 specification, 1998 edition, Section 22. The eZ80F91 MCU
supports the IEEE 802.3 protocol with the following exception:

The eZ80F91 MCU does not support the Giga Media Independent Interface (GMII)
referred to in the following sections of the IEEE 802.3 1998 version: section 22.1.5, section 22.2.4, section 22.2.4.1.2, section 22.2.4.1.5, and section 22.2.4.1.6.
The EMAC is used for many different applications, including network interface, ethernet
switching, and test equipment designs. The EMAC includes the following blocks:
•
•
PS019215-0910
Central clock and reset module (not shown in the block diagram).
Host memory interface and transmit/receiver arbiter.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
288
•
•
•
FIFO buffer and DMA control blocks for transmit and receive.
802.3x media access control block.
MII interface management.
The media access control block implements 802.3x flow control functions for both transmit and receive.
The MII management module provides a two-wire control/status path to the MII PHY.
Read and Write communication to and from registers within the PHY is accomplished via
the host interface.
Note:
MII PHY is a Physical Layer transceiver device; PHY does not refer to the eZ80F91 system clock output pin, PHI.
The MII management module provides a two-wire control/status path to the MII. Read
and Write communication to and from registers within the PHY is accomplished via the
host interface.
EMAC Functional Description
The EMAC block implements memory, arbiter, and transmit and receive direct memory
access functions, and offers four communication modes: HALF-DUPLEX, FULLDUPLEX, NIBBLE, and ENDEC. In HALF-DUPLEX and FULL-DUPLEX modes,
throughput occurs at both 10 Mbps and 100 Mbps speeds. Throughput in ENDEC and
NIBBLE modes occurs at 10 Mbps. A brief description of these four modes are as follows:
10/100 Mbps HALF-DUPLEX Mode— In this mode, data are transferred only in one
direction at a time; that is, one can either transmit or receive, but both cannot occur
simultaneously.
10/100 Mbps FULL-DUPLEX Mode— In this mode, data are transmitted and received at
the same time.
10 Mbps ENDEC Mode— This mode affects the MII interface between the PHY and the
MAC. In ENDEC mode, the RxCLK and TxCLK clocks are bit clocks instead of the normal nibble clock. In NIBBLE mode, 4 bits are transferred on each clock. In ENDEC
mode, 1 bit is transferred per clock.
For more information on throughput, see EMAC and the System Clock on page 296.
Memory
EMAC memory is the shared Ethernet memory location of the Transmit and Receive buffers. This memory is broken into two parts: the Tx buffer and the Rx buffer. The Transmit
Lower Boundary Pointer Register, EmacTLBP, is the register that holds the starting
address of the Tx buffer. The Boundary Pointer Register, EmacBP, points to the start of the
Rx buffer (end of Tx buffer + 1). The Receive High Boundary Pointer Register,
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
289
EmacRHBP, points to the end of the Rx buffer + 1. The Tx and Receive buffers are
divided into packet buffers of either 256, 128, 64, or 32 bytes. These buffer sizes are
selected by EmacBufSize register bits 7 and 6.
The EmacBlksLeft register contains the number of Receive packet buffers remaining in
the Rx buffer. This buffer is used for software flow control. If the Block_Level is nonzero
(bits 5:0 of the EmacBufSize register), hardware flow control is enabled. If in FULLDUPLEX mode, the EMAC transmits a pause control frame when the EmacBlksLeft register is less than the Block_Level. In HALF-DUPLEX mode, the EMAC continually transmits a nibble pattern of hexadecimal 5’s to jam the channel.
Four pointers are defined for reading and writing the Tx and Rx buffers. The Transmit
Write Pointer, TWP, is a software pointer that points to the next available packet buffer.
The TWP is reset to the value stored in EmacTLBP. The Transmit Read Pointer, TRP, is a
hardware pointer in the Transmit Direct Memory Access Register, TxDMA, that contains
the address of the next packet to be transmitted. It is automatically reset to the EmacTLBP.
The Receive Write Pointer, RWP, is a hardware pointer in the Receive Direct Memory
Access Register, RxDMA, which contains the storage address of the incoming packet. The
RWP pointer is automatically initialized to the Boundary Pointer registers. The Receive
Read Pointer, RRP, is a software pointer to where the next packet must be read from. The
RRP pointer must be initialized to the Boundary Pointer registers. For the hardware flow
control to function properly, the software must update the hardware RRP (EmacRrp)
pointer whenever the software version is updated. The RxDMA uses RWP and the RRP to
determine how many packet buffers remain in the Rx buffer.
Arbiter
The arbiter controls access to EMAC memory. It prioritizes the requests for memory
access between the CPU, the TxDMA, and the RxDMA. The TxDMA offers two levels of
priority: a high priority when the TxFIFO is less than half full and a Low priority when the
TxFIFO is more than half full. Similarly, the RxDMA offers two levels of priority: a high
priority when the RxFIFO is more than half full and a Low priority when the RxFIFO is
less than half full.
The arbiter determines resolution between the CPU, the RxDMA, and the TxDMA
requests to access EMAC memory. Post writing for CPU Writes results in Zero-Wait-state
write access timing when the CPU assumes the highest priority. CPU Reads require a minimum of 1 Wait state and takes more when the CPU does not hold the highest priority. The
CPU Read Wait state is not a user-controllable operation, because it is controlled by the
arbiter. The RxDMA and TxDMA requests are not allowed to occur back-to-back. Therefore, the maximum throughput rate for the two Direct Memory Access (DMA) ports is 25
Mbps each (one byte every 2 clocks) when the system clock is running at 50 MHz. The
rate is reduced to 20 MBps for a 40 MHz system clock. The arbiter uses the internal WAIT
signal to add Wait states to CPU access when required. See Table 174 on page 290.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
290
Table 174. Arbiter Priority
Priority
Level
Device
Serviced
Flags
0
RxDMA High
RxFIFO > half full (FAF)
1
TxDMA High
TxFIFO < half full (FAE)
2
®
eZ80 CPU
3
RxDMA Low
RxFIFO < half full (FAE)
4
TxDMA Low
TxFIFO > half full (FAF)
TxDMA
The TxDMA module moves the next packet to be transmitted from EMAC memory into
the TxFIFO. Whenever the polling timer expires, the TxDMA reads the High status byte
from the Tx descriptor table pointed to by the Transmit Read Pointer, TRP. Polling continues until the High status Read reaches bit 7, when the Emac_Owns ownership semaphore,
bit 15 of the descriptor table (see Table 178 on page 295) is set to 1. The TxDMA then initializes the packet length counter with the size of the packet from descriptor table bytes 3
and 4. The TxDMA moves the data into the TxFIFO until the packet length counter downcounts to zero. The TxDMA then waits for Transmission Complete signal to be asserted to
indicate that the packet is sent and that the Transmit status from the EMAC is valid. The
TxDMA updates the descriptor table status and resets the ownership semaphore, bit 15.
Finally, the Tx_DONE_STAT bit of the EMAC Interrupt Status Register is set to 1, the
address field, DMA_Address, is updated from the descriptor table next pointer, NP (see
Figure 62 on page 294). The High byte of the status is read to determine if the next packet
is ready to be transmitted.
While the TxDMA is filling the TxFIFO, it monitors two signals from the Transmit FIFO
State Machine (TxFifoSM) to detect error conditions and to determine if the packet is to
be retransmitted (TxDMA_Retry asserted) or the packet is aborted (TxDMA_Abort
asserted). If the packet is aborted, the TxDMA updates the descriptor status and moves to
the next packet. If the packet is to be retried, the DMA_Address is reset to the start of the
packet, the packet length counter is reloaded from the descriptor table, bytes 3 and 4, and
the packet is moved into the TxFIFO again. When an abort or retry event occurs, the
TxDMA asserts the appropriate signal to reset the TxFIFO Read and Write pointers which
clears out any data that is in the FIFO. The TxFifoSM negates the TxDMA_Abort or
TxDMA_Retry signal(s) or both when the TxFCWP signal is High. This handshaking
maintains synchronization between the TxDMA and the TxFifoSM.
RxDMA
The RxDMA reads the data from the RxFIFO and stores it in the EMAC memory Receive
buffer. When the end of the packet is detected, the RxDMA reads the next two bytes from
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
291
the RxFIFO and writes them into the Rx descriptor status LSB and MSB. The packetlength counter is stored into the descriptor table’s Packet Length field, and the descriptor
table’s next pointer is written into the Rx descriptor table. Additionally, the
Rx_DONE_STAT bit in the EMAC Interrupt Status Register is set to 1.
Signal Termination
When the EMAC interface is not used, the MII signals must be terminated as listed in
Table 175. Terminated pins are either left unconnected (float) or tied to ground.
MDIO is controlled by the MDC output signal. When the EMAC is not being used, these
two pins are not driven. The RX_DV, RX_ER, and RXD[3:0] inputs are controlled by the
rising edge of the RX_CLK input signal. When RX_CLK is tied to Ground, these pins do
not affect the EMAC. The TX_EN, TX_ER, and TXD[3:0] outputs are controlled by the
rising edge of the TX_CLK input signal. When TX_CLK is tied to Ground, these pins do
not affect the EMAC. The CRS and COL input pins have no relationship to the clock, and
therefore must be placed into nonactive states and tied to Ground.
Table 175. MII Signal Termination When EMAC is Not Used
PS019215-0910
Signal
Pin Type
Termination
Direction
MDIO
Bidirectional
Float
MDC
Output pin
Float
RX_DV
Input pin
Float
CRS
Input pin
Ground
RX_CLK
Input pin
Ground
RX_ER
Input pin
Float
RXD[3:0]
Input pins
Float
COL
Input pin
Ground
TX_CLK
Input pin
Ground
TX_EN
Output pin
Float
TXD[3:0]
Output pins
Float
TX_ER
Output pin
Float
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
292
EMAC Interrupts
Eight different sources of interrupts from the EMAC are listed in Table 176.
Table 176. EMAC Interrupts
Interrupt
Description
EMAC System Interrupts
Transmit State Machine Error
Bit 7 (TxFSMERR_STAT) of the EMAC Interrupt Status Register
(EMAC_ISTAT). A Transmit State Machine Error must not occur.
However, if this bit is set, the entire transmitter module must be
reset.
MIIMGT Done
Bit 6 (MGTDONE_STAT) of the Interrupt Status Register
(EMAC_ISTAT). This bit is set when communicating to the PHY
over the MII during a Read or Write operation.
Receive Overrun
Bit 2 (Rx_OVR_STAT) of the Interrupt Status Register
(EMAC_ISTAT). If this bit is set, all incoming packets are ignored
until this bit is cleared by software.
EMAC Transmitter Interrupts
Transmit Control Frame
Transmit Control Frame = Bit 1 (Tx_CF_STAT) of the Interrupt
Status Register (EMAC_ISTAT). Denotes when control frame
transmission is complete.
Transmit Done
Bit 0 (Tx_DONE_STAT) of the Interrupt Status Register
(EMAC_ISTAT). Denotes when packet transmission is complete.
EMAC Receiver Interrupts
Receive Packet
Bit 5 (Rx_CF_STAT) of the Interrupt Status Register
(EMAC_ISTAT). Denotes when packet reception is complete.
Receive Pause Packet
Bit 4 (Rx_PCF_STAT) of the Interrupt Status Register
(EMAC_ISTAT). Denotes when pause packet reception is
complete.
Receive Done
Bit 3 (Rx_DONE_STAT) of the Interrupt Status Register
(EMAC_ISTAT). Denotes when packet reception is complete.
EMAC Shared Memory Organization
Internal Ethernet SRAM shares memory with the CPU. This memory is divided into the
Transmit buffer and the Receive buffer by defining three registers, as listed below.
PS019215-0910
•
Transmit Lower Boundary Pointer (TLBP)—this register points to the start of the
Transmit buffer in the internal Ethernet shared memory space.
•
Boundary Pointer (BP)—this register points to the start of the Receive buffer.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
293
•
Receive High Boundary Pointer (RHBP)—this register points to the end of the Receive
buffer + 1.
Figure 60 displays the internal Ethernet shared memory.
Upper Memory Address
RHBP
Rx Buffer
BP
Tx Buffer
TLBP
Lower Memory Address
Figure 60. Internal Ethernet Shared Memory
The Transmit and Receive buffers are subdivided into packet buffers of 32, 64, 128, or 256
bytes in size. The packet buffer size is set in bits 7 and 6 of the EmacBufSize register. An
Ethernet packet accommodate multiple packet buffers. First, however, a brief listing of the
contents of a typical Ethernet packet is in order. See Table 177.
Table 177. Ethernet Packet Contents
Byte Range
Contents
Bytes 0–5
MAC destination address.
Bytes 6–11
MAC source address.
Bytes 12–13
Length/Type field.
Bytes 14–n
MAC Client Data.
Bytes (n+1)–(n+4)
Frame Check Sequence.
At the start of each packet is a descriptor table that describes the packet. Each actual
Ethernet packet follows the descriptor table as displayed in Figure 61 on page 294.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
294
Offset
Ethernet
Packet
0007h
Descriptor
Table
TWP
0000h
Figure 61. Descriptor Table
Note:
For an official description of an Ethernet packet, refer to IEEE 802.3 specification, Figure
3-1.
The descriptor table contains three entries: the next pointer (NP), the packet size
(Pkt_Size), and the packet status (Stat), as displayed in Figure 62.
Offset
Stat
0005h
Pkt_Size
0003h
NP
TWP
0000h
Figure 62. Descriptor Table Entries
NP is a 24-bit pointer to the start of the next packet. Pkt_Size contains the number of bytes
of data in the Ethernet packet, including the four CRC bytes, but does not contain the
seven descriptor table bytes. Stat contains the status of the packet. Stat differs for Transmit
and Receive packets. See Table 178 on page 295 and Table 179 on page 295.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
295
Table 178. Transmit Descriptor Status
Bit
Name
Description
15
TxOwner
0 = Host (eZ80®) owns, 1 = EMAC owns.
14
TxAbort
1 = Packet aborted (not transmitted).
13
TxBPA
1 = Back pressure applied.
12
TxHuge
1 = Packet size is very large (Pkt_Size > EmacMaxf).
11
TxLOOR
1 = Type/Length field is out of range (larger than 1518 bytes).
10
TxLCError
1 = Type/Length field is not a Type field and it does not match the
actual data byte length of the Ethernet packet. The data byte length is
the number of bytes of data in the Ethernet packet between the Type/
Length field and the FCS.
9
TxCrcError
1 = The packet contains an invalid FCS (CRC). This flag is set when
CRCEN = 0 and the last 4 bytes of the packet are not the valid FCS.
8
TxPktDeferred
1 = Packet is deferred.
7
TxXsDfr
1 = Packet is excessively deferred. (> 6071 nibble times in 100 BaseT
or 24,287 bit times in 10 BaseT).
6
TxFifoUnderRun
1 = TxFIFO experiences underrun. Check the TxAbort bit to see if the
packet is aborted or retried.
5
TxLateCol
1 = A late collision occurs. Collision is detected at a byte count >
EmacCfg2[5:0]. Collisions detected before the byte count reaches
EmacCfg2[5:0] are early collisions and retried.
4
TxMaxCol
1 = The maximum number of collisions occurs. # Collisions >
EmacCfg3[3:0]. These packets are aborted.
[3:0]
TxNumberOfCollisions
This field contains the number of collisions that occur while transmitting
the packet.
Table 179. Receive Descriptor Status
Bit
Name
Description
15
RxOK
1 = Packet received intact.
14
RxAlignError
1 = An odd number of nibbles is received.
13
RxCrcError
1 = The CRC (FCS) is in error.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
296
Table 179. Receive Descriptor Status (Continued)
Bit
Name
Description
12
RxLongEvent
1 = A Long or Dropped Event occurs. A Long Event is when a packet
over 50,000 bit times occurs. A Dropped Packet occurs if the minimum
interpacket gap is not met, the preamble is not pure, and the
EmacCfg3[PUREP] bit is set, or if a preamble over 11 bytes in length is
detected and the EmacCfg3[LONGP] bit is set to 1.
11
RxPCF
1 = The packet is a pause control frame.
10
RxCF
1 = The packet is a control frame.
9
RxMcPkt
1 = The packet contains a multicast address.
8
RxBcPkt
1 = The packet contains a broadcast address.
7
RxVLAN
1 = The packet is a VLAN packet.
6
RxUOpCode
1 = An unsupported opcode is indicated in the opcode field of the
Ethernet packet.
5
RxLOOR
1 = The Type/Length field is out of range (larger than 1518 bytes).
4
RxLCError
1 = Type/Length field is not a Type field and it does not match the
actual data byte length of the Ethernet packet. The data byte length is
the number of bytes of data in the Ethernet packet between the Type/
Length field and the FCS.
3
RxCodeV
1 = A code violation is detected. The PHY asserts Rx error (RxER).
2
RxCEvent
1 = A carrier event is previously seen. This event is defined as Rx error
RxER = 1, receive data valid (RxDV) = 0 and receive data (RxD) = Eh.
1
RxDvEvent
1 = A receive data (RxDV) event is previously seen. Indicates that the
last Receive event is not long enough to be a valid packet.
0
RxOVR
1 = A Receive overrun occurs in this packet. An overrun occurs when
all of the EMAC Receive buffers are in use and the Receive FIFO is full.
The hardware ignores all incoming packets until the EmacIStat
Register [Rx_Ovr] bit is cleared by the software. There is no indication
as to how many packets are ignored.
EMAC and the System Clock
Effective Ethernet throughput in any given system is dependent upon factors such as system clock speed, network protocol overhead, application complexity, and network traffic
conditions at any given moment. The following information provides a general guideline
about the effects of system clock speed on Ethernet operation.
The eZ80F91 MCU's EMAC block performs a synchronous function that is designed to
operate over a wide range of system clock frequencies. To understand its maximum data
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
297
transfer capabilities at certain system operating frequencies, you must first understand the
internal data bus bandwidth that is required under ideal conditions.
For 10 BaseT Ethernet connectivity, the data rate is 10 Mbps, which equates to 1.25 Mbps.
If the eZ80F91 MCU is operating in FULL-DUPLEX mode over 10BaseT, the data rate for
RX data and TX data is 1.25 Mbps. Because raw data transfers at this rate consume a certain amount of CPU bandwidth, the CPU must support traffic from both directions as well
as operate at a minimum clock frequency of (1.25 + 1.25) * 2 = 5 MHz while transferring
Ethernet packets to and from the physical layer.
Similarly, for 100 BaseT Ethernet, the data rate is 100 Mbps, which equates to 12.5 Mbps.
If the eZ80F91 MCU is operating in FULL-DUPLEX mode over 100 BaseT, the data rate
for RX data and TX data is 12.5 Mbps. Because raw data transfers at this rate consume a
certain amount of CPU bandwidth, the CPU must support traffic from both directions as
well as operate at a minimum clock frequency of (12.5 + 12.5) x 2 = 50 MHz while transferring Ethernet packets to and from the physical layer. Consequently, 50 MHz is the minimum system clock speed that the eZ80® CPU requires to sustain EMAC data transfers
while not including any software overhead or additional eZ80 tasks.
The FIFO functionality of the EMAC operates at any frequency as long as the user application avoids overrun and underrun errors via higher-level flow control. Actual application requirements will dictate Ethernet modes of operation (FULL-DUPLEX, HALFDUPLEX, etc.). Because each user and application is different, it becomes your responsibility to control the data flow with these parameters. Under ideal conditions, the system
clock will operate somewhere between 5 MHz and 50 MHz to handle the EMAC data
rates.
EMAC Operation in HALT Modes
When the CPU is in HALT mode, the eZ80F91 device’s EMAC block cannot be disabled
as other peripherals. Upon receipt of an Ethernet packet, a maskable Receive interrupt is
generated by the EMAC block, just as it would be in a non-halt mode. Accordingly, the
processor wakes up and continues with the user-defined application.
EMAC Registers
After a system reset, all EMAC registers are set to their default values. Any Writes to
unused registers or register bits are ignored and reads return a value of 0. For compatibility with future revisions, unused bits within a register must always be written with a value
of 0. Read/Write attributes, reset conditions, and bit descriptions of all of the EMAC registers are provided in this section.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
298
EMAC Test Register
The EMAC Test Register allows test functionality of the EMAC block. Available test
modes are defined for bits [6:0]. See Table 180.
Table 180. EMAC Test Register (EMAC_ TEST = 0020h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Note: R/W = Read/Write, R = Read Only.
Bit 
Position
Value
Description
7
0
Reserved.
6
TEST_FIFO
0
FIFO test mode disabled—Normal operation.
1
FIFO test mode enabled.
5
TxRx_SEL
0
Select the Receive FIFO when FIFO test mode is enabled.
1
Select the Transmit FIFO when FIFO test mode is enabled.
4
SSTC
0
Normal operation.
1
Short Cut Slot Timer Counter. Slot time is shortened to
speed up simulation.
3
SIMR
0
Normal operation.
1
Simulation Reset.
2
0
FRC_OVR_ERR
1
Normal operation.
1
0
FRC_UND_ERR
1
Normal operation.
0
LPBK
PS019215-0910
Force Overrun error in Receive FIFO.
Force Underrun error in Transmit FIFO.
0
Normal operation.
1
EMAC Transmit interface is looped back into EMAC Receive
interface.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
299
EMAC Configuration Register 1
The EMAC Configuration Register 1 allows control of the padding, autodetection, cyclic
redundancy checking (CRC) control, full-duplex, field length checking, maximum packet
ignores, and proprietary header options. See Table 181.
Table 181. EMAC Configuration Register 1 (EMAC_CFG1 = 0021h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
0
No padding. Assume all frames presented to EMAC have
proper length.
1
EMAC pads all short frames by adding zeroes to the end of the
data field. This bit is used in conjunction with ADPADN and
VLPAD.
6
ADPADN
0
Disable autodetection.
1
Enable frame detection by comparing the two bytes following
the source address with 0x8100 (VLAN Protocol ID) and pad
accordingly. This bit is ignored if PADEN is cleared to 0.
5
VLPAD
0
Do not pad all short frames.
1
EMAC pads all short frames to 64 bytes and append a valid
CRC. This bit is ignored if PADEN is cleared to 0.
4
CRCEN
0
Do not append CRC.
1
Append CRC to every frame regardless of padding options.
3
FULLD
0
HALF-DUPLEX mode. CSMA/CD is enabled.
1
Enable FULL-DUPLEX mode. CSMA/CD is disabled.
2
FLCHK
0
Ignore the length field within Transmit/Receive frames.
1
Both Transmit and Receive frame lengths are compared to the
length/type field. If the length/type field represents a length
then the frame length check is performed.
1
HUGEN
0
Limit the Receive frame-size to the number of bytes specified
in the MAXF[15:0] field.
1
Allow unlimited sized frames to be received. Ignore the
MAXF[15:0] field.
7
PADEN
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
300
Bit 
Position
0
DCRCC
Value
Description
0
No proprietary header. Normal operation.
1
Four bytes of proprietary header, ignored by CRC, exists on
the front of IEEE 802.3 frames.
Table 182 lists the results of different settings for bits [7:4] of EMAC Configuration Register 1.
Table 182. CRC/PAD Features of EMAC Configuration Register
ADPADN
VLPADN
PADEN
0
0
0
0
No pad or CRC appended.
0
0
0
1
CRC appended.
0
0
1
0
Pad to 60 bytes if necessary; append CRC (min. size = 64).
0
0
1
1
Pad to 60 bytes if necessary; append CRC (min. size = 64).
0
1
0
0
No pad or CRC appended.
0
1
0
1
CRC appended.
0
1
1
0
Pad to 64 bytes if necessary, append CRC (min. size = 68).
0
1
1
1
Pad to 64 bytes if necessary, append CRC (min. size = 68).
1
0
0
0
No pad or CRC appended.
1
0
0
1
CRC appended.
1
0
1
0
If VLAN not detected, pad to 60, add CRC.
If VLAN detected, pad to 64, add CRC.
1
0
1
1
If VLAN not detected, pad to 60, add CRC.
If VLAN detected, pad to 64, add CRC.
1
1
0
0
No pad or CRC appended.
1
1
0
1
CRC appended.
1
1
1
0
If VLAN not detected, pad to 60, add CRC.
If VLAN detected, pad to 64, add CRC.
1
1
1
1
If VLAN not detected, pad to 60, add CRC.
If VLAN detected, pad to 64, add CRC.
PS019215-0910
CRCEN Result
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
301
EMAC Configuration Register 2
The EMAC Configuration Register 2 controls the behavior of the back pressure and late
collision data from the Descriptor table. See Table 183.
Table 183. EMAC Configuration Register 2 (EMAC_CFG2 = 0022h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
1
1
0
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
0
Use normal back-off algorithm prior to transmitting packet. No
back pressure applied.
1
After incidentally causing a collision during back pressure, the
EMAC immediately (that is, no back-off) retransmits the packet
without back-off, which reduces the chance of further collisions
and ensures that the Transmit packets are sent.
6
NOBO
0
Enable exponential back-off.
1
The EMAC immediately retransmits following a collision rather
than use the binary exponential backfill algorithm, as specified
in the IEEE 802.3 specification.
[5:0]
LCOL
00h–3Fh Sets the number of bytes after Start Frame Delimiter (SFD) for
which a late collision occurs. By default, all late collisions are
aborted.
7
BPNB
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
302
EMAC Configuration Register 3
The EMAC Configuration Register 3 controls preamble length and value, excessive deferment, and the number of retransmission tries. See Table 184.
Table 184. EMAC Configuration Register 3 (EMAC_CFG3 = 0023h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
0
The EMAC allows any preamble length as per the IEEE 802.3
specification.*
1
The EMAC only allows Receive packets that contain preamble
fields less than 12 bytes in length.*
6
PUREP
0
No preamble error checking is performed.
1
The EMAC verifies the content of the preamble to ensure that it
contains a value of 55h and that it is error-free. Packets
containing an errored preamble are discarded.
5
XSDFR
0
The EMAC aborts when the excessive deferral limit is reached.
1
The EMAC defers to the carrier indefinitely as per the IEEE
802.3 specification.
4
BITMD
0
Disable 10 Mbps ENDEC mode.
1
Enable 10 Mbps ENDEC mode.
[3:0]
RETRY
0h–Fh
A programmable field specifying the number of retransmission
attempts following a collision before aborting the packet due to
excessive collisions.
7
LONGP
Note: IEEE 802.3 specifies a minimum of 56 bits of preamble. A maximum number of bits is not defined. For details, see the IEEE 802.3 Specification, Section 7.2.3.2.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
303
EMAC Configuration Register 4
The EMAC Configuration Register 4 controls pause control frame behavior, back
pressure, and receive frame acceptance. See Table 185.
Table 185. EMAC Configuration Register 4 (EMAC_CFG4 = 0024h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value
Description
7
0
Reserved.
6
TPCF
0
Do not transmit a pause control frame.
1
Transmit pause control frame (FULL-DUPLEX mode). TPCF
continually sends pause control frames until negated.
5
THDF
0
Disable back pressure.
1
EMAC asserts back pressure on the link. Back pressure
causes preamble to be transmitted, raising carrier sense
(HALF-DUPLEX mode).
4
PARF
0
Only accept frames that meet preset criteria (that is, address,
CRC, length, etc.).
1
All frames are received regardless of address, CRC, length,
etc.
3
RxFC
0
EMAC ignores received pause control frames.
1
EMAC acts upon pause control frames received.
2
TxFC
0
PAUSE control frames are not allowed to be transmitted.
1
PAUSE control frames are allowed to be transmitted.
1
TPAUSE
0
Do not force a pause condition.
1
Force a pause condition while this bit is asserted.
0
RxEN
0
EMAC receiver disabled.
1
EMAC receiver enabled.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
304
EMAC Station Address Register
The EMAC Station Address register is used for two functions. In the address recognition logic for Receive frames, EMAC_STAD_0–EMAC_STAD_5 are matched against
the sixth byte Destination Address (DA) field of the Receive frame. EMAC_STAD_0 is
matched against the first byte of the Receive frame, and EMAC_STAD_5 is matched
against the sixth byte of the Receive frame. Bit 0 of EMAC_STAD_0 (STAD[40]) is
matched against the first bit (Unicast/Multicast bit) of the first byte of the Receive
frame. This bit ordering is used to logically map the PE-MACMII station address as
illustrated below.
EMAC_STAD0[7:0] contains STAD[47:40]
....
....
EMAC_STAD5[7:0] contains STAD[7:0]
The second function of the EMAC Station Address registers is to provide the Source
Address (SA) field of Transmit Pause frames when these frames are transmitted by the
EMAC. EMAC_STAD_0 provides the first byte of the 6 byte SA field and
EMAC_STAD_5 provides the final byte of the SA field in order of transmission. The LSB
is the first byte sent out. The EMAC Station Address register is listed in Table 186.
Table 186. EMAC Station Address Register (EMAC_STAD_0 = 0025h, EMAC_STAD_1 =
0026h, EMAC_STAD_2 = 0027h, EMAC_STAD_3 = 0028h, EMAC_STAD_4 = 0029h,
EMAC_STAD_5 = 002Ah)
Bit
7
6
5
4
3
2
1
0
EMAC_STAD_0 Reset
0
0
0
0
0
0
0
0
EMAC_STAD_1 Reset
0
0
0
0
0
0
0
0
EMAC_STAD_2 Reset
0
0
0
0
0
0
0
0
EMAC_STAD_3 Reset
0
0
0
0
0
0
0
0
EMAC_STAD_4 Reset
0
0
0
0
0
0
0
0
EMAC_STAD_5 Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
305
Bit 
Position
Value
[7:0]
EMAC_STAD_x
Description
00h–FFh This 48-bit station address comprises {EMAC_STAD_5,
EMAC_STAD_4, EMAC_STAD_3, EMAC_STAD_2,
EMAC_STAD_1, EMAC_STAD_0}.
EMAC Transmit Pause Timer Value Register—Low and High Bytes
The Low and High bytes of the EMAC Transmit Pause Timer Value Register are inserted
into outgoing pause control frames. See Table 187 and Table 188.
Table 187. EMAC Transmit Pause Timer Value Register—Low Byte (EMAC_TPTV_L = 002Bh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_TPTV_L
Value
Description
00h–FFh The 16-bit value, {EMAC_TPTV_H, EMAC_TPTV_L}, is
inserted into outgoing pause control frames as the pause
timer value upon asserting TPCF.
Table 188. EMAC Transmit Pause Timer Value Register—High Byte (EMAC_TPTV_H = 002Ch)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_TPTV_H
PS019215-0910
Value
Description
00h–FFh The 16-bit value, {EMAC_TPTV_H, EMAC_TPTV_L}, is
inserted into outgoing pause control frames as the pause
timer value upon asserting TPCF.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
306
EMAC Interpacket Gap
EMAC Interpacket Gap Overview
Interpacket Gap (IPG) is measured between the last nibble of the frame check sequence
(FCS) and the first nibble of the preamble of the next packet. Three registers are available
to fine tune the IPG, the EMAC_IPGT, EMAC_IPGR1, and the EMAC_IPGR2. The first
register EMAC_IPGT determines the back-to-back Transmit IPG. The other two registers
determine the non-back-to-back IPG in two parts. Table 189 lists the values for the
EMAC_IPGT and the corresponding IPGs for both FULL-DUPLEX and HALF-DUPLEX
modes.
Table 189. EMAC_IPGT Back-to-Back Settings for Full- and Half-Duplex Modes
MII, RMII/SMII, PMD
(100 Mbps)
MII, RMII/SMII
(10 Mbps)
ENDEC Mode
(10 Mbps)
Clock Period = 40 ns
IPGT[6:0]
Clock Period = 400 ns
IPGT[6:0]
Clock Period = 100 ns
IPGT[6:0]
Half
Duplex
*12h
Full
Duplex
Interpacket
Gap
0Dh
Half
Duplex
Full
Duplex
Interpacket
Gap
0.12 µs
00h
0Bh
0.44 µs
0Ch
Full
Duplex
Interpacket
Gap
1.2 µs
10h
1.9 µs
08h
4.4 µs
18h
2.7 µs
0.60 µs
0Ch
6.0 µs
20h
3.5 µs
10h
0.76 µs
10h
7.5 µs
40h
6.7 µs
15h
0.96 µs
15h
9.6 µs
5Dh
9.6 µs
20h
1.40 µs
20h
14.0 µs
20h
13.0 µs
12h
Half
Duplex
5Ah
Note: *The IEEE 802.3, 802.3(u) minimum values are shaded.
The equations for back-to-back Transmit IPG are determined by the following:
FULL-DUPLEX Mode (3 clocks + IPGT clocks) * clock period = IPG
HALF-DUPLEX Mode (6 clocks + IPGT clocks) * clock period = IPG
Table 190 on page 307 lists the IPGR2 settings for the non-back-to-back packets.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
307
Table 190. EMAC_IPGT Non-Back-to-Back Settings for Full- /Half-Duplex Modes
MII, RMII/SMII, PMD
(100 Mbps)
MII, RMII/SMII
(10 Mbps)
ENDEC Mode
(10 Mbps)
Clock Period = 40 ns
Clock Period = 400 ns
Clock Period = 100 ns
IPGR2[6:0]
Interpacket
Gap
IPGR2[6:0]
Interpacket
Gap
IPGR2[6:0]
Interpacket
Gap
00h
0.24 µs
00h
2.4 µs
00h
0.6 µs
10h
0.88 µs
10h
8.8 µs
10h
2.2 µs
*12h
0.96 µs
12h
9.6 µs
20h
3.8 µs
20h
1.52 µs
20h
15.2 µs
40h
7.0 µs
40h
2.80 µs
40h
28.0 µs
5Ah
9.6 µs
7Fh
5.32 µs
7Fh
53.2 µs
7Fh
13.3 µs
Note: *The IEEE 802.3, 802.3(u) minimum values are shaded.
A non-back-to-back Transmit IPG is determined by the following formula:
(6 clocks + IPGR2 clocks) * clock period = IPG
The difference in values between Table 189 on page 306 and Table 190 is due to the
asynchronous nature of the Carrier Sense (CRS). The CRS must undergo a 2-clock
synchronization before the internal Tx state machine detects it. This synchronization
equates to a 6-clock intrinsic delay between packets instead of the 3-clock intrinsic delay
in the back-to-back packet mode. More information covering this topic is found in the
IEEE 802.3/4.2.3.2.1 Carrier Deference section.
EMAC Interpacket Gap Register
The EMAC Interpacket Gap (IPG) is a programmable field representing the IPG between
back-to-back packets. It is the IPG parameter used in FULL-DUPLEX and HALFDUPLEX modes between back-to-back packets. Set this field to the appropriate number
of IPG bytes. The default setting of 15h represents the minimum IPG of 0.96 µs
(at 100 Mbps) or 9.6 s (at 10 Mbps). See Table 191.
Table 191. EMAC Interpacket Gap Register (EMAC_IPGT = 002Dh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
1
0
1
0
1
CPU Access
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
308
Bit
Position
Value
Description
7
0
Reserved.
[6:0]
IPGT
00h–7Fh The number of bytes of IPG.
EMAC Non-Back-To-Back IPG Register—Part 1
Part 1 of the EMAC non-back-to-back IPG Register is a programmable field representing
the optional carrier sense window referenced in IEEE 802.3/4.2.3.2.1 Carrier Deference. If
a carrier is detected during the timing of IPGR1, the EMAC defers to the carrier. If, however, the carrier becomes active after IPGR1, the EMAC continues timing for IPGR2 and
transmits, knowingly causing a collision. This collision acts to ensure fair access to the
medium. Its range of values is 00h to IPGR2. See Table 192. The default setting of 0Ch
represents the Carrier Sense Window Referencing depicted tin IEEE 802.3, Section
4.2.3.2.1.
Table 192. EMAC Non-Back-To-Back IPG Register—Part 1 (EMAC_IPGR1 = 002Eh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
1
1
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write
Bit
Position
Value
Description
7
0
Reserved.
[6:0]
IPGR 1
00h–
7Fh
This is a programmable field representing the optional carrier
sense window referenced in IEEE 802.3/4.2.3.2.1 Carrier
Deference.
EMAC Non-Back-To-Back IPG Register—Part 2
Part 2 of the EMAC non-back-to-back IPG Register is a programmable field representing
the non-back-to-back IPG. Its default is 12h, which represents the minimum IPG of
0.96 µs at 100 Mbps or 9.6 µs at 10 Mbps. See Table 193 on page 309.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
309
Table 193. EMAC Non-Back-To-Back IPG Register—Part 2 (EMAC_IPGR2 = 002Fh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
1
0
0
1
0
CPU Access
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit
Position
Value
Description
7
0
Reserved.
[6:0]
IPGR2
00h–7Fh This bit range is a programmable field representing the nonback-to-back interpacket gap.
EMAC Maximum Frame Length Register—Low and High Bytes
The 16-bit field resets to 0600h, which represents a maximum Receive frame of 1536
bytes. An untagged maximum size Ethernet frame (packet) is 1518 bytes. A tagged frame
adds four bytes for a total of 1522 bytes. If a shorter maximum length restriction is more
appropriate, program this field. See Table 194 and Table 195 on page 310.
Note:
The default value of 1536 bytes is large enough to cover the largest Ethernet packet, which
contains 14 bytes of Ethernet header, 1500 bytes of MAC client data, plus 4 bytes of CRC
for a total of 1518 maximum bytes. This value is also large enough to cover VLAN frames
with prepended headers up to 18 bytes.
VLAN frames have a proprietary header prepended to the Ethernet packet. Setting the
DCRCC bit in EMAC_CFG1 will exclude the first 4 bytes—the proprietary header—from
the CRC calculation. For VLAN packets, the maximum frame length is 1522, 4 more than
for normal Ethernet packets due to the 4 byte prepended header. Normal packets feature a
12 byte header before the MAC client data. For more information about this topic, refer to
Figure 3-1 of the IEEE 802.3 specification.
If a proprietary header is allowed, this field must be adjusted accordingly. For example, if
12 byte headers are prepended to frames, MAXF must be set to 1524 bytes to allow the
maximum VLAN tagged frame plus the 12 byte header. The default value of 1536 is large
enough to cover the largest Ethernet packet: 14 bytes of Ethernet header, 1500 bytes of
MAC client data, plus 4 bytes of CRC for a total of 1518 bytes maximum. It is also large
enough to cover VLAN packets with prepended headers up to 18 bytes. The following formulas illustrate:
Ethernet Packet— Maximum frame size = normal Ethernet packet – 14 (Ethernet header)
+ 1500 (MAC client data) + 4 (CRC) = 1518 bytes
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
310
VLAN Packet— Maximum frame size = VLAN with 4 byte header – 4 (VLAN header) +
14 (Ethernet header) + 1500 MAC client data) + 4 (CRC) = 1522 bytes.
Table 194. EMAC Maximum Frame Length Register—Low Byte (EMAC_MAXF_L = 0030h
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:0]
EMAC_MAXF_L
Value
Description
00h–FFh These bits represent the Low byte of the 2 byte MAXF
value, {EMAC_MAXF_H, EMAC_MAXF_L}. Bit 7 is bit 7 of
the 16-bit value. Bit 0 is bit 0 (lsb) of the 16-bit value.
Table 195. EMAC Maximum Frame Length Register—High Byte (EMAC_MAXF_H = 0031h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
1
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
Value
[7:0]
00h–
EMAC_MAXF_H FFh
PS019215-0910
Description
These bits represent the High byte of the 2 byte MAXF
value, {EMAC_MAXF_H, EMAC_MAXF_L}. Bit 7 is bit 15
(msb) of the 16-bit value. Bit 0 is bit 8 of the 16-bit value.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
311
EMAC Address Filter Register
The EMAC Address Filter Register functions as a filter to control Promiscuous mode, and
multicast and broadcast messaging. See Table 196.
Table 196. EMAC Address Filter Register (EMAC_AFR = 0032h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value
Description
[7:4]
0h
Reserved.
3
PROM
1
Enable Promiscuous Mode. Receive all incoming packets
regardless of station address. Disables station address
filtering.
0
Disable Promiscuous Mode.
1
Accept any multicast message. A multicast packet is
determined by the first bit in the destination address. If the first
LSB is a 1, it is a group address and is globally or locally
administered depending on the 2nd bit. For more information,
see IEEE 802.3/3.2.3.
0
Do not accept multicast messages of any type.
1
Accept only qualified multicast (QMC) messages as
determined by the hash table.
0
Do not accept QMC messages.
1
Accept broadcast messages. Broadcast messages have the
destination address set to FFFFFFFFFFFFh.
0
Do not accept broadcast messages.
2
MC
1
QMC
0
BC
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
312
EMAC Hash Table Register
The EMAC Hash Table Register represents the 8x8 hash table matrix. This table is used as
an option to select between different multicast addresses. If a multicast address is
received, the first 6 bits of the CRC are decoded and added to a table that points to a single
bit within the hash table matrix. If the selected bit = 1, the multicast packet is accepted. If
the bit = 0, the multicast packet is rejected. See Table 197.
Table 197. EMAC Hash Table Register (EMAC_HTBL_0 = 0033h, EMAC_HTBL_1 = 0034h,
EMAC_HTBL_2 = 0035h, EMAC_HTBL_3 = 0036h, EMAC_HTBL_4 = 0037h, EMAC_HTBL_5
= 0038h, EMAC_HTBL_6 = 0039h, EMAC_HTBL_7 = 003Ah)
Bit
7
6
5
4
3
2
1
0
EMAC_HTBL_0 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_1 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_2 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_3 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_4 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_5 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_6 Reset
0
0
0
0
0
0
0
0
EMAC_HTBL_7 Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write
Bit 
Position
Value
Description
[7:0]
EMAC_HTBL_x
00h–
FFh
This field is the hash table. The 64 bit hash table is
{EMAC_HTBL_7, EMAC_HTBL_6, EMAC_HTBL_5,
EMAC_HTBL_4, EMAC_HTBL_3, EMAC_HTBL_2,
EMAC_HTBL_1, EMAC_HTBL_0}.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
313
EMAC MII Management Register
The EMAC MII Management Register is used to control the external PHY attached to the
MII. See Table 198.
Table 198. EMAC MII Management Register (EMAC_MIIMGT = 003Bh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
7
LCTLD
6
RSTAT
5
SCINC
4
SCAN
3
SPRE
PS019215-0910
Value
Description
1
Rising edge causes the CTLD control data to be transmitted to
external PHY if MII is not busy. This bit is self clearing.
0
No operation.
1
Rising edge causes status to be read from external PHY via
PRSD[15:0] bus if MII is not busy. This bit is self clearing.
0
No operation.
1
Scan PHY address increments upon SCAN cycle. The SCAN
bit must also be set for the PHY address to increment after
each scan. The scanning starts at the EMAC_FIAD and
increments up to 1Fh. It then returns to the EMAC_FIAD
address.
0
Normal operation.
1
Perform continuous Read cycles via MII management. While in
SCAN mode, the EMAC_ISTAT[MGTDONE] bit is set when the
current PHY Read has completed. At this time, the
EMAC_PRSD register holds the Read data and the
EMAC_MIISTAT[4:0] holds the address of the PHY for which
the EMAC_PRSD data pertains.
0
Normal operation.
1
Suppress the MDO preamble. MDO is management data
output, an internal signal driven from the MDIO pin.
0
Normal preamble.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
314
Bit
Position
Value
[2:0]
CLKS
Description
Programmable divisor that produces MDC from SCLK. MDC is the
management data clock pin, which clocks MDIO data to and from the
PHY. Its frequency is SCLK divided by the MDC clock divider.
000
MDC = SCLK ÷ 4.
001
MDC = SCLK ÷ 4.
010
MDC = SCLK ÷ 6.
011
MDC = SCLK ÷ 8.
100
MDC = SCLK ÷ 10.
101
MDC = SCLK ÷ 14.
110
MDC = SCLK ÷ 20.
111
MDC = SCLK ÷ 28.
EMAC PHY Configuration Data Register—Low and High Byte
The Low and High bytes of the EMAC PHY Configuration Data Register represents the
configuration data written to the external PHY. The EMAC_CTLD_H and
EMAC_CTLD_L registers form a 16-bit register. These registers are loaded with data to
be sent via the MDIO pin to the PHY. The PHY is selected by setting the EMAC_FIAD.
The register inside the PHY is selected by setting EMAC_RGAD. See Table 199 and
Table 200 on page 315.
Table 199. EMAC PHY Configuration Data Register—Low Byte (EMAC_CTLD_L = 003Ch)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
EMAC_CTLD_L
00h–
FFh
These bits represent the Low byte of the 2 byte PHY
configuration data value, {EMAC_CTLD_H,
EMAC_CTLD_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit
0 (lsb) of the 16 bit value.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
315
Table 200. EMAC PHY Configuration Data Register—High Byte (EMAC_CTLD_H = 003Dh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
EMAC_CTLD_H
00h–
FFh
These bits represent the High byte of the 2 byte PHY
configuration data value, {EMAC_CTLD_H,
EMAC_CTLD_L}. Bit 7 is bit 15 (msb) of the 16 bit value. Bit
0 is bit 8 of the 16 bit value.
EMAC PHY Address Register
The EMAC PHY Address Register allows access to the external PHY registers. See
Table 201.
Table 201. EMAC PHY Address Register (EMAC_RGAD = 003Eh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value
Description
[7:5]
000
Reserved.
[4:0]
RGAD
00h–
1Fh
Programmable 5 bit value which selects address within the
selected external PHY.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
316
EMAC PHY Unit Select Address Register
The EMAC PHY Unit Select Address Register allows the selection of multiple connected
external PHY devices. See Table 202.
Table 202. EMAC PHY Unit Select Address Register (EMAC_FIAD = 003Fh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value
Description
[7:5]
000
Reserved.
[4:0]
FIAD
00h–1Fh Programmable 5-bit value that selects an external PHY.
EMAC Transmit Polling Timer Register
This register sets the Transmit Polling Period in increments of TPTMR = SYSCLK ÷ 256.
Whenever this register is written, the status of the Transmit Buffer Descriptor is checked
to determine if the EMAC owns the Transmit buffer. It then rechecks this status every
TPTMR (calculated by TPTMR x EMAC_PTMR[7:0]). The Transmit Polling Timer is
disabled if this register is set to 00h (which also disables the transmitting of packets). If a
transmission is in progress when EMAC_PTMR is set to 00h, the transmission will complete. See Table 203.
Table 203. EMAC Transmit Polling Timer Register (EMAC_PTMR = 0040h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_PTMR
PS019215-0910
Value
Description
00h–FFh The Transmit polling period.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
317
EMAC Reset Control Register
The bit values in the EMAC Reset Control Register are not self-clearing bits. You are
responsible for controlling their state. See Table 204.
Table 204. EMAC Reset Control Register (EMAC_RST = 0041h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
1
0
0
0
0
0
CPU Access
R
R
R/W
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit
Position
Value
Description
[7:6]
00
Reserved
5
SRST
1
Software Reset Active—resets Receive, Transmit, EMAC
Control and EMAC MII_MGT functions
0
Normal operation
4
HRTFN
1
Reset Transmit function
0
Normal operation
3
HRRFN
1
Reset Receive function
0
Normal operation
2
HRTMC
1
Reset EMAC Transmit Control function
0
Normal operation
1
HRRMC
1
Reset EMAC Receive Control function
0
Normal operation
0
HRMGT
1
Reset EMAC Management function
0
Normal operation
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
318
EMAC Transmit Lower Boundary Pointer Register—Low and High Bytes
The EMAC Transmit Lower Boundary Pointer is set to the start of the Transmit buffer in
EMAC shared memory. See Table 205 and Table 206.
Table 205. EMAC Transmit Lower Boundary Pointer Register—Low Byte (EMAC_TLBP_L = 0042h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R
R
R
R
R
CPU Access
Note: R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
EMAC_TLBP_L
00h–
FFh
These bits represent the Low byte of the 2 byte Transmit
Lower Boundary Pointer value, {EMAC_TLBP_H,
EMAC_TLBP_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit 0
(lsb) of the 16 bit value.
Table 206. EMAC Transmit Lower Boundary Pointer Register—High Byte (EMAC_TLBP_H
= 0043h)*
Bit
7
6
5
4
3
2
1
0
Reset
1
1
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
EMAC_TLBP_H
00h–
FFh
These bits represent the High byte of the 2 byte Transmit
Lower Boundary Pointer value, {EMAC_TLBP_H,
EMAC_TLBP_L}. Bit 7 is bit 15 (msb) of the 16 bit value. Bits
7:5 default to 000 on reset; bit 0 is bit 8 of the 16-bit value.
Note: *Bits 7:5 are not used by the EMAC; these bits return 000.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
319
EMAC Boundary Pointer Register—Low and High Bytes
The Boundary Pointer is set to the start of the Receive buffer (end of Transmit buffer +1)
in EMAC shared memory. This pointer is 24 bits and determined by {RAM_ADDR_U,
EMAC_BP_H, EMAC_BP_L}. The upper 3 bits of the EMAC_BP_H register are hardwired inside the eZ80F91 device to locate the base of EMAC shared memory. The last 5
bits of the EMAC_BP_L register value are hard-wired to keep the addressing aligned to
a 32 byte boundary. See Table 207 and Table 208.
Table 207. EMAC Boundary Pointer Register—Low Byte (EMAC_BP_L = 0044h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R
R
R
R
R
CPU Access
Note: R = Read Only, R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_BP_L
Value
Description
00h–FFh These bits represent the Low byte of the 3 byte EMAC
Boundary Pointer value, {EMAC_BP_U, EMAC_BP_H,
EMAC_BP_L}. Bit 7 is bit 7 of the 24 bit value. Bit 0 is bit 0 of
the 24 bit value.
Table 208. EMAC Boundary Pointer Register—High Byte (EMAC_BP_H = 0045h)
Bit
15:13
12:8
Reset
1
1
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only, R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_BP_H
Value
Description
00h–FFh These bits represent the High byte of the 3 byte EMAC
Boundary Pointer value, {EMAC_BP_U, EMAC_BP_H,
EMAC_BP_L}. Bit 7 is bit 15 of the 24 bit value. Bit 0 is bit 8 of
the 24 bit value.
EMAC Boundary Pointer Register—Upper Byte
The EMAC Boundary Pointer Register maps directly to the RAM_ADDR_U register
within the eZ80F91 device. This register value is Read Only. See Table 209 on page 320.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
320
Table 209. EMAC Boundary Pointer Register—Upper Byte (EMAC_BP_U = 0046h)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
1
1
1
1
1
1
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
EMAC_BP_U
Value
Description
00h–FFh These bits represent the upper byte of the 3 byte EMAC
Boundary Pointer value, {EMAC_BP_U, EMAC_BP_H,
EMAC_BP_L}. Bit 7 is bit 23 of the 24 bit value. Bit 0 is bit 16 of
the 24 bit value.
EMAC Receive High Boundary Pointer Register—Low and High Bytes
The Receive High Boundary Pointer Register must be set to the end of the Receive buffer
+1 in EMAC shared memory. This RHBP uses the same RAM_ADDR_U as the
EMAC_BP_U pointer above. See Table 210 and Table 211 on page 321.
Table 210. EMAC Receive High Boundary Pointer Register—Low Byte (EMAC_RHBP_L = 0047h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R
R
R
R
R
CPU Access
Note: R = Read Only, R/W = Read/Write
Bit 
Position
[7:0]
EMAC_RHBP_L
PS019215-0910
Value
Description
00h–E0h These bits represent the Low byte of the 2 byte EMAC
Receive High Boundary Pointer value, {EMAC_RHBP_H,
EMAC_RHBP_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit
0 (lsb) of the 16 bit value.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
321
Table 211. EMAC Receive High Boundary Pointer Register—High Byte (EMAC_RHBP_H = 0048h)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only, R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
00h–FFh These bits represent the High byte of the 2 byte EMAC
EMAC_RHBP_H
Receive High Boundary Pointer value, {EMAC_RHBP_H,
EMAC_RHBP_L}. Bit 7 is bit 15 (msb) of the 16 bit value. Bit
0 is bit 8 of the 16 bit value.
Note: *Bits 7:5 are not used by the EMAC; these bits return 000 upon reset.
EMAC Receive Read Pointer Register—Low and High Bytes
The Receive Read Pointer Register must be initialized to the EMAC_BP value (start of the
Receive buffer). This register points to where the next Receive packet is read from. The
EMAC_BP[12:5] is loaded into this register whenever the EMAC_RST [(HRRFN) is set
to 1. The RxDMA block uses the Emac_Rrp[12:5] to compare to EmacRwp[12:5] for
determining how many buffers remain. The result equates to the EmacBlksLeft register.
See Table 212 and Table 213 on page 322.
Table 212. EMAC Receive Read Pointer Register—Low Byte (EMAC_RRP_L = 0049h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R
R
R
R
R
CPU Access
Note: R = Read Only, R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_RRP_L
PS019215-0910
Value
Description
00h–FFh These bits represent the Low byte of the 2 byte EMAC
Receive Read Pointer value, {EMAC_RRP_H,
EMAC_RRP_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit 0
(lsb) of the 16 bit value.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
322
Table 213. EMAC Receive Read Pointer Register—High Byte (EMAC_RRP_H = 004Ah)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R/W
R/W
R/W
R/W
R/W
Note: R = Read Only, R/W = Read/Write.
Bit 
Position
Value
Description
[7:0]
00h–FFh These bits represent the High byte of the 2-byte EMAC
EMAC_RRP_H
Receive Read Pointer value, {EMAC_RRP_H,
EMAC_RRP_L}. Bit 7 is bit 15 (msb) of the 16-bit value. Bits
7:5 default to 000 on reset; bit 0 is bit 8 of the 16-bit value.
EMAC Buffer Size Register
The lower six bits of this register set the level at which the EMAC either transmits a pause
control frame or jams the Ethernet bus, depending on the mode selected. When each of
these bits contain a zero, this feature is disabled.
In FULL-DUPLEX mode, a Pause Control Frame is transmitted as a One-shot operation.
The software must free up a number of Rx buffers so that the number of buffers remaining,
EmacBlksLeft, is greater than TCPF_LEV.
In HALF-DUPLEX mode, the EMAC jams the Ethernet by sending a continuous stream
of hexadecimal 5s (5fh). When the software frees up the Rx buffers and the number of
buffers remaining, EmacBlksLeft, is greater than TCPF_LEV, the EMAC stops jamming.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
323
Table 214. EMAC Buffer Size Register (EMAC_BUFSZ = 004Bh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
[7:6]
BUFSZ
[5:0]
TPCF_LEV
Value
Description
00
Set EMAC Rx/Tx buffer size to 256 bytes.
01
Set EMAC Rx/Tx buffer size to 128 bytes.
10
Set EMAC Rx/Tx buffer size to 64 bytes.
11
Set EMAC Rx/Tx buffer size to 32 bytes.
00h–3Fh Transmit Pause Control Frame level. 00h disables the
hardware generated transmit pause control frame.
EMAC Interrupt Enable Register
Enabling the Receive Overrun interrupt allows software to detect an overrun condition
as soon as it occurs. If this interrupt is not set, then an overrun cannot be detected until
the software processes the Receive packet with the overrun and checks the Receive status in the Rx descriptor table. Because the receiver is disabled by an overrun error until
the Rx_OVR bit is cleared in the EMAC_ISTAT register, this packet is the final packet
in the Receive buffer. To re-enable the receiver before all of the Receive packets are
processed and the Receive buffer is empty, software enables this interrupt to detect the
overrun condition early. As it processes the Receive packets, it re-enables the receiver
when the number of free buffers is greater than the number of minimum buffers. See
Table 215 on page 324.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
324
Table 215. EMAC Interrupt Enable Register (EMAC_IEN = 004Ch)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
Value
Description
1
Enable Transmit State Machine Error Interrupt (system
interrupt).
0
Disable Transmit State Machine Error Interrupt (system
interrupt).
6
MGTDONE
1
Enable MII Management. Done Interrupt (system Interrupt).
0
Disable MII Management. Done Interrupt (system Interrupt).
5
Rx_CF
1
Enable Receive Control Frame Interrupt (Receive interrupt).
0
Disable Receive Control Frame Interrupt (Receive interrupt).
4
Rx_PCF
1
Enable Receive Pause Control Frame interrupt (Receive
interrupt).
0
Disable Receive Pause Control Frame interrupt (Receive
interrupt).
3
Rx_DONE
1
Enable Receive Done interrupt (Receive interrupt).
0
Disable Receive Done interrupt (Receive interrupt).
2
Rx_OVR
1
Enable Receive Overrun interrupt (System interrupt).
0
Disable Receive Overrun interrupt (System interrupt).
1
Tx_CF
1
Enable Transmit Control Frame Interrupt (Transmit interrupt).
0
Disable Transmit Control Frame Interrupt (Transmit interrupt).
0
Tx_DONE
1
Enable Transmit Done interrupt (Transmit interrupt).
0
Disable Transmit Done Interrupt (Transmit interrupt).
7
TxFSMERR
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
325
EMAC Interrupt Status Register
When a Receive overrun occurs, all incoming packets are ignored until the
Rx_OVR_STAT status bit is cleared by software. Consequently, software controls when
the receiver is re-enabled after an overrun. Enable the Rx_OVR interrupt to detect overrun
conditions when they occur. Clear this condition when the Rx buffers are freed to avoid
additional overrun errors. See Table 216.
Note:
Status bits are not self-clearing. Each status bit is cleared by writing a 1 into the selected
bit.
Table 216. EMAC Interrupt Status Register (EMAC_ISTAT = 004Dh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit
Position
Value
Description
1
An internal error occurs in the EMAC Transmit path. The
Transmit path must be reset to reset this error condition.
0
Normal operation—no Transmit state machine errors.
1
The MII Management interrupt has completed a Read
(RSTAT or SCAN) or a Write (LDCTLD) access to the
PHY.
0
The MII Management interrupt does not occur.
1
Receive Control Frame interrupt (Receive Interrupt)
occurs.
0
Receive Control Frame interrupt does not occur.
1
Receive Pause Control Frame interrupt (Receive
Interrupt) occurs.
0
Disable Receive Pause Control Frame interrupt (Receive
Interrupt) does not occur.
3
Rx_DONE_STAT
1
Receive Done interrupt (Receive Interrupt) occurs.
0
Disable Receive Done interrupt (Receive Interrupt) does
not occur.
2
Rx_OVR_STAT
1
Receive Overrun interrupt (System Interrupt) occurs.
0
Receive Overrun interrupt (System Interrupt) does not
occur.
7
TxFSMERR_STAT
6
MGTDONE_STAT
5
Rx_CF_STAT
4
Rx_PCF_STAT
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
326
Bit
Position
1
Tx_CF_STAT
0
Tx_DONE_STAT
Value
Description
1
Transmit Control Frame Interrupt (Transmit Interrupt)
occurs.
0
Transmit Control Frame Interrupt (Transmit Interrupt)
does not occur.
1
Transmit Done interrupt (Transmit Interrupt) occurs.
0
Transmit Done interrupt (Transmit Interrupt) does not
occur.
EMAC PHY Read Status Data Register—Low and High Bytes
The PHY MII Management Data Register is where the data Read from the PHY is stored.
See Table 217 and Table 218 on page 327.
Table 217. EMAC PHY Read Status Data Register—Low Byte (EMAC_PRSD_L = 004Eh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
EMAC_PRSD_L
PS019215-0910
Value
Description
00h–FFh These bits represent the Low byte of the 2 byte EMAC PHY
Read Status Data value, {EMAC_PRSD_H,
EMAC_PRSD_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit
0 (lsb) of the 16 bit value.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
327
Table 218. EMAC PHY Read Status Data Register—High Byte (EMAC_PRSD_H = 004Fh)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
Value
Description
[7:0]
00h–FFh These bits represent the High byte of the 2-byte EMAC
EMAC_PRSD_H
PHY Read Status Data value, {EMAC_PRSD_H,
EMAC_PRSD_L}. Bit 7 is bit 15 (msb) of the 16-bit value.
Bit 0 is bit 8 of the 16-bit value.
EMAC MII Status Register
The EMAC MII Status Register is used to determine the current state of the external PHY
device. See Table 219.
Table 219. EMAC MII Status Register (EMAC_MIISTAT = 0050h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit
Position
7
BUSY
6
MIILF
PS019215-0910
Value
Description
1
MII management operation in progress—Busy. This status bit
goes busy whenever the LCTLD (PHY Write) or the RSTAT
(PHY Read) is set in the EMAC_MIIMGT register. It is
negated when the Write or Read operation to the PHY has
completed. In SCAN mode, the BUSY will be asserted until
the SCAN is disabled. Use the EmacIStat[MGTDONE]
interrupt status bit to determine when the data is valid.
0
Not Busy.
1
Local copy of PHY Link fail bit.
0
PHY Link OK.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
328
5
NVALID
1
MII Scan result is not valid Emac_PRSD is invalid
0
Emac_PRSD is valid.
[4:0]
RDADR
00h–1Fh Denotes PHY addressed in current scan cycle.
EMAC Receive Write Pointer Register—Low Byte
The Read Only Receive-Write-Pointer register reports the current RxDMA Receive Write
pointer. This pointer gets initialized to EmacTLBP whenever Emac_RST bits SRST or
HRRTN are set. Because the size of the packet is limited to a minimum of 32 bytes, the
last five bits are always zero. See Table 220 and Table 221 on page 329.
Table 220. EMAC Receive Write Pointer Register—Low Byte (EMAC_RWP_L = 0051h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
Value
Description
[7:0]
EMAC_RWP_L
00h–
E0h
These bits represent the Low byte of the 2 byte EMAC
RxDMA Receive Write Pointer value, {EMAC_RWP_H,
EMAC_RWP_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit 0
(lsb) of the 16 bit value.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
329
EMAC Receive Write Pointer Register—High Byte
Because of the size of the EMAC’s 8 KB SRAM, the upper three bits of the EMAC
Receive Write Pointer Register are always zero.
Table 221. EMAC Receive Write Pointer Register—High Byte (EMAC_RWP_H = 0052h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
Value
[7:0]
EMAC_RWP_H
Description
00h–1Fh These bits represent the High byte of the 2 byte EMAC
RxDMA Receive Write Pointer value, {EMAC_RWP_H,
EMAC_RWP_L}. Bit 7 is bit 15 (msb) of the 16 bit value. Bit
0 is bit 8 of the 16 bit value.
EMAC Transmit Read Pointer Register—Low Byte
The Low byte of the Transmit Read Pointer register reports the current TxDMA Transmit
Read pointer.This pointer is initialized to EmacTLBP whenever Emac_RST bits SRST or
HRRTN are set. Because the size of the packet is limited to a minimum of 32 bytes, the
last five bits are always zero. See Table 222.
Table 222. EMAC Transmit Read Pointer Register—Low Byte (EMAC_TRP_L = 0053h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
EMAC_TRP_L
PS019215-0910
Value
Description
00h–E0h These bits represent the Low byte of the 2 byte EMAC
TxDMA Transmit Read Pointer value, {EMAC_TRP_H,
EMAC_TRP_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is bit 0
(lsb) of the 16 bit value.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
330
EMAC Transmit Read Pointer Register—High Byte
Because of the size of the EMAC’s 8 KB SRAM, the upper three bits of the EMAC Transmit Read Pointer Register are always zero. See Table 223.
Table 223. EMAC Transmit Read Pointer Register—High Byte (EMAC_TRP_H = 0054h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
RO
RO
RO
RO
RO
RO
RO
RO
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_TRP_H
Value
Description
00h–1Fh These bits represent the High byte of the 2 byte EMAC
TxDMA Transmit Read Pointer value, {EMAC_TRP_H,
EMAC_TRP_L}. Bit 7 is bit 15 (msb) of the 16 bit value. Bit
0 is bit 8 of the 16 bit value.
EMAC Receive Blocks Left Register—Low and High Bytes
This register reports the number of buffers left in the Receive EMAC shared memory. The
hardware uses this information along with the block-level set in the EMAC_BUFSZ register to determine when to transmit a pause control frame. Software uses this information to
determine when it must request that a pause control frame be transmitted (by setting bit 6
of the EMAC_CFG4 register). For the BlksLeft logic to operate properly, the Receive
buffer must contain at least one more packet buffer than the number of packet buffers
required for the largest packet. That is, one packet cannot fill the entire Receive buffer.
Otherwise, the BlksLeft will be in error. See Table 224 and Table 225 on page 331.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
331
Table 224. EMAC Receive Blocks Left Register—Low Byte (EMAC_BLKSLFT_L = 0055h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
EMAC_BLKSLFT_L
Value
Description
00h–FFh These bits represent the Low byte of the 2 byte EMAC
Receive Blocks Left value, {EMAC_BLKSLFT_H,
EMAC_BLKSLFT_L}. Bit 7 is bit 7 of the 16 bit value. Bit
0 is bit 0 (lsb) of the 16 bit value.
Table 225. EMAC Receive Blocks Left Register—High Byte (EMAC_BLKSLFT_H = 0056h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
0
0
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit 
Position
[7:0]
EMAC_BLKSLFT_H
PS019215-0910
Value
Description
00h–FFh These bits represent the High byte of the 2 byte EMAC
Receive Blocks Left value, {EMAC_BLKSLFT_H,
EMAC_BLKSLFT_L}. Bit 7 is bit 15 (msb) of the 16 bit
value. Bit 0 is bit 8 of the 16 bit value.
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
332
EMAC FIFO Data Register—Low and High Bytes
The FIFO Read/Write Test Access Data Register allows writing and reading the FIFO
selected by the EMAC_TEST TxRx_SEL bit when the EMAC_TEST register
TEST_FIFO bit is set. See Table 226 and Table 227.
Table 226. EMAC FIFO Data Register—Low Byte (EMAC_FDATA_L = 0057h)
Bit
7
6
5
4
3
2
1
0
Reset
X
X
X
X
X
X
X
X
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CPU Access
Note: R/W = Read/Write.
Bit 
Position
[7:0]
EMAC_FDATA_L
Value
Description
00h–FFh These bits represent the Low byte of the 10 bit EMAC
FIFO data value, {EMAC_FDATA_H[1:0],
EMAC_FDATA_L}. Bit 7 is bit 7 of the 16 bit value. Bit 0 is
bit 0 (lsb) of the 10 bit value.
Table 227. EMAC FIFO Data Register—High Byte (EMAC_FDATA_H = 0058h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
0
0
0
0
X
X
CPU Access
R
R
R
R
R
R
R/W
R/W
Note: R = Read Only; R/W = Read/Write.
Bit 
Position
Value
Description
[7:2]
00h
Reserved.
[1:0]
EMAC_FDATA_H
0h–3h
These bits represent the upper two bits of the 10 bit EMAC
FIFO data value, {EMAC_FDATA_H[1:0],
EMAC_FDATA_L}. Bit 1 is bit 9 (msb) of the 16 bit value.
Bit 0 is bit 8 of the 10 bit value.
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
333
EMAC FIFO Flags Register
The FIFO Flags value is set in the EMAC hardware to half full, or 16 bytes. See Table 228.
Table 228. EMAC FIFO Flags Register (EMAC_FFLAGS = 0059h)
Bit
7
6
5
4
3
2
1
0
Reset
0
0
1
1
0
0
1
1
CPU Access
R
R
R
R
R
R
R
R
Note: R = Read Only.
Bit
Position
Value
Description
7
TFF
1
Transmit FIFO full
0
Transmit FIFO not full
6
0
Reserved
5
TFAE
1
Transmit FIFO almost empty
0
Transmit FIFO not almost empty
4
TFE
1
Transmit FIFO empty
0
Transmit FIFO not empty
3
RFF
1
Receive FIFO full
0
Receive FIFO not full
2
RFAF
1
Receive FIFO almost full
0
Receive FIFO not almost full
1
RFAE
1
Receive FIFO almost empty
0
Receive FIFO not almost empty
0
RFE
1
Receive FIFO empty
0
Receive FIFO not empty
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
334
PS019215-0910
Ethernet Media Access Controller
eZ80F91 MCU
Product Specification
335
On-Chip Oscillators
The eZ80F91 features two on-chip oscillators for use with an external crystal. The primary
oscillator generates the system clock for the internal CPU and the majority of the on-chip
peripherals. Alternatively, the XIN input pin also accepts a CMOS-level clock input signal.
If an external clock generator is used, the XOUT pin must be left unconnected. The secondary oscillator drives a 32 kHz crystal to generate the time-base for the Real-Time Clock.
Primary Crystal Oscillator Operation
Figure 63 on page 336 displays a recommended configuration for connection with an
external 50 MHz, 3rd-overtone, parallel-resonant crystal. Recommended crystal specifications are provided in Table 229 on page 336 and Table 230 on page 337. Printed circuit
board layout must add not more than 4 pF of stray capacitance to either the XIN or XOUT
pins. If oscillation does not occur, try removing C1 for testing and decreasing the value of
C2 by the estimated stray capacitance to decrease loading.
PS019215-0910
On-Chip Oscillators
eZ80F91 MCU
Product Specification
336
On-Chip Oscillator
XIN
XOUT
50 MHz Crystal
(Third Overtone)
C 1 = 5 pF
R = 100 Kȍ
(this value is not critical)
L = 3.3 —H (± 10%)
C 2 = 10-15 pF
C3 = .01-0.1 —F
Figure 63. Recommended Crystal Oscillator Configuration—50 MHz Operation
Table 229. Recommended Crystal Oscillator Specifications—1 MHz Operation
Parameter
Frequency
Dependent Value
Units
Frequency
1
MHz
Resonance
Parallel
Mode
Fundamental
Series Resistance (RS)
750
Ohms
Maximum
Load Capacitance (CL)
13
pF
Maximum
PS019215-0910
Comments
On-Chip Oscillators
eZ80F91 MCU
Product Specification
337
Table 229. Recommended Crystal Oscillator Specifications—1 MHz Operation
(Continued)
Parameter
Frequency
Dependent Value
Units
Comments
Shunt Capacitance (C0)
7
pF
Maximum
Drive Level
1
mW
Maximum
Table 230. Recommended Crystal Oscillator Specifications—10 MHz Operation
Parameter
Frequency
Dependent Value
Units
Frequency
10
MHz
Resonance
Parallel
Mode
Fundamental
Series Resistance (RS)
35
Ohms
Maximum
Load Capacitance (CL)
30
pF
Maximum
Shunt Capacitance (C0)
7
pF
Maximum
Drive Level
1
mW
Maximum
Comments
32 kHz Real-Time Clock Crystal Oscillator Operation
Figure 64 on page 338 displays a recommended configuration for connecting the RealTime Clock oscillator with an external 32 kHz, fundamental mode, parallel-resonant crystal. The recommended crystal specifications are provided in Table 231on page 338. A
printed circuit board layout must not add more than 4 pF of stray capacitance to either the
RTC_XIN or RTC_XOUT pins. If oscillation does not occur, reduce the values of capacitors C1 and C2 to decrease loading.
An on-chip MOS resistor sets the crystal drive current limit. This configuration does not
require an external bias resistor across the crystal. An on-chip MOS resistor provides the
biasing.
PS019215-0910
On-Chip Oscillators
eZ80F91 MCU
Product Specification
338
RTC_XIN
RTC_XOUT
32 kHz Crystal
(Fundamental Mode)
C1 = 10 pF
C2 = 10 pF
Figure 64. Recommended Crystal Oscillator Configuration—32 kHz Operation
Table 231. Recommended Crystal Oscillator Specifications—32 kHz Operation
Parameter
Value
Units
Comments
Frequency
32
kHz
32768 Hz
Resonance
Parallel
Mode
Fundamental
Series Resistance (RS)
50
k
Maximum
Load Capacitance (CL)
12.5
pF
Maximum
Shunt Capacitance (C0)
3
pF
Maximum
Drive Level
1
µW
Maximum
PS019215-0910
On-Chip Oscillators
eZ80F91 MCU
Product Specification
339
Electrical Characteristics
Absolute Maximum Ratings
Stresses greater than those listed in Table 232 causes permanent damage to the device.
These ratings are stress ratings only. Operation of the device at any condition outside those
indicated in the operational sections of these specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods affects device reliability. For
improved reliability, unused inputs must be tied to one of the supply voltages (VDD or
VSS).
Table 232. Absolute Maximum Ratings
Parameter
Minimum Maximum
Units
Notes
1
Ambient temperature under bias (ºC)
–40
+105
ºC
Storage temperature (ºC)
–65
+150
C
Voltage on any pin with respect to VSS
–0.3
+5.5
V
Voltage on VDD pin with respect to VSS
–0.3
+3.6
V
Total power dissipation
830
mW
Maximum current out of VSS
230
mA
Maximum current into VDD
230
mA
Maximum current on input and/or inactive output pin
–15
+15
µA
Maximum output current from active output pin
–8
+8
mA
Flash memory Writes to Same Single Address
—
2
—
100
—
Years
10,000
—
Cycles
Flash Memory Data Retention
Flash Memory Write/Erase Endurance
2
3
4
Notes
1. Operating temperature is specified in DC Characteristics.
2. This voltage applies to all pins except XIN and XOUT.
3. Before next erase operation.
4. Write cycles.
DC Characteristics
Table 233 on page 340 lists the DC characteristics of the eZ80F91 device.
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
340
Table 233. DC Characteristics
Symbol Parameter
TA =
0 ºC to 70 ºC
TA =
–40 ºC to 105 ºC
Minimum
Typ2
Typ2
3.3
Maximum Minimum
Maximum Units Conditions
VDD
Supply Voltage
3.0
VIL
Low Level
Input Voltage
VIH
High Level
Input Voltage
VOL
Low Level
Output Voltage
VOH
High Level
Output Voltage
2.4
VRTC
RTC Supply
Voltage
2.0
3.6
2.0
3.6
V
IIL
Input Leakage
Current
–10
+10
–10
+10
A
VDD = 3.6 V; 
VIN = VDD or
VSS1
ITL
Open-drain
Leakage Current
–10
+10
–10
+10
A
VDD = 3.6 V
ICC a
Active Current
26
40
mA
@ 10 MHz
52
80
mA
@ 20 MHz
137
190
mA
@ 50 MHz
15
20
mA
@ 10 MHz
27
40
mA
@ 20 MHz
75
100
mA
@ 50 MHz
ICC h
3.6
3.0
–0.3
0.3 x VDD
0.7 x VDD
5.5
3.3
3.6
V
–0.3
0.3 x VDD
V
0.7 x VDD
5.5
V
0.4
V
VDD = 3.0 V;
IOL = 1 mA
V
VDD = 3.0 V;
IOH = –1 mA
0.4
2.4
HALT Mode
Current
ICC s
SLEEP Mode
Current
2.5
20
2.5
95
A
VBO_OFF=1
(VBO
disabled)
IRTC
RTC Supply
Current
2.5
10
2.5
10
A
Supply current
into VRTC
1This
condition excludes all pins with on-chip pull-ups when driven Low.
Values in Typical column are for Vdd = 3.3 V and TA = 25 ºC.
2
POR and VBO Electrical Characteristics
Table 234 on page 341 lists the Power-On Reset and Voltage Brownout characteristics of
the eZ80F91 device.
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
341
Table 234. POR and VBO Electrical Characteristics
TA = –40 ºC to 105 ºC
Minimum
Typ
VBO Voltage Threshold
2.45
2.65
2.90
V
VCC = VVBO
VPOR
POR Voltage Threshold
2.55
2.75
2.95
V
VCC = VPOR
VHYST
POR/VBO Hysteresis
30
100
120
mV
TANA
POR/VBO analog RESET duration
40
100
s
TVBO_MIN
VBO pulse reject period
10
IPOR_VBO
POR/VBO DC current consumption
40
50
A
ISPOR_VBO POR/VBO DC SLEEP mode current
consumption
120
150
A
100
V/ms
Symbol
Parameter
VVBO
VCCRAMP
VCC ramp rate requirements to
guarantee proper RESET occurs
Maximum Unit Conditions
0.1
s
VBO_OFF=0
(VBO enabled)
Flash Memory Characteristics
Table 235 lists the Flash memory characteristics of the eZ80F91 device. For Flash
programming and erase timing information, see Flash Memory on page 97.
Table 235. Flash Memory Electrical Characteristics and Timing
VDD = 3.0 V to 3.6 V;
TA = –40 ºC to 105 ºC
Symbol
Flash Byte Read Cycle Time
Minimum
Typical
Maximum
Units
78
—
—
ns
Notes
Current Consumption Under Various Operating Conditions
Figure 65 on page 342 displays the typical current consumption of the eZ80F91 device
versus Vdd while operating at 25 ºC, with zero Wait states, and with either a 10 MHz,
20 MHz, or 50 MHz system clock.
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
342
eZ80F91 Active Idd vs CLK Freq @ Vdd (25C)
180.00
Actve Idd (Icca) (mA)
160.00
140.00
120.00
100.00
80.00
60.00
40.00
20.00
0.00
10Mhz
20Mhz
50Mhz
Frequency (MHz)
Vdd=2.9V
Vdd=3.3V
Vdd=3.7V
Figure 65. ICC vs. System Clock Frequency During ACTIVE Mode
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
343
Figure 66 displays the typical current consumption of the eZ80F91 device versus system
clock frequency while operating in HALT mode.
e Z80F 91 HALT M ode Idd vs CLK Fre q @ V dd (25C)
100.00
90.00
HALT Mode Idd (Icch) (mA)
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
10Mhz
20Mhz
50Mhz
Fr e q u e n cy (M Hz )
V dd=2.9V
V dd=3.3V
V dd=3.7V
Figure 66. ICC vs. System Clock Frequency During HALT Mode
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
344
Figure 67 displays the typical current consumption of the eZ80F91 device versus Vdd
while operating in SLEEP mode (units in microamps, 10-6A); all peripherals off, and VBO
disabled.
e Z8 0 F 9 1 S L EEP M o d e Id d v s V d d (2 5 C )
2 .6 5
SLEEP Mode Idd (Iccs) (uA)
2 .6 0
2 .5 5
2 .5 0
2 .4 5
2 .4 0
2 .3 5
2 .3 0
2 .2 5
2 .2 0
2 .1 5
2 .9
3 .3
3 .7
V d d (V )
Ic c s ( V B O d is a b le d )
Figure 67. ICC vs. Vdd During SLEEP Mode
AC Characteristics
This section provides information about the AC characteristics and timing of the
eZ80F91 device. All AC timing information assumes a standard load of 50 pF on all
outputs. See Table 236.
Table 236. AC Characteristics
TA =
0 ºC to 70 ºC
Symbol Parameter
Minimum Maximum Minimum Maximum Units Conditions
TXIN
System Clock 
Cycle Time
20
TXINH
System Clock 
High Time
8
TXINL
System Clock 
Low Time
8
PS019215-0910
TA =
–40 ºC to 105 ºC
1000
20
1000
ns
VDD = 3.0–3.6 V
8
ns
VDD = 3.0–3.6 V;
TCLK = 20 ns
8
ns
VDD = 3.0–3.6 V;
TCLK = 20 ns
Electrical Characteristics
eZ80F91 MCU
Product Specification
345
Table 236. AC Characteristics (Continued)
TA =
0 ºC to 70 ºC
Symbol Parameter
TA =
–40 ºC to 105 ºC
Minimum Maximum Minimum Maximum Units Conditions
TXINR
System Clock 
Rise Time
3
3
ns
VDD = 3.0–3.6 V;
TCLK = 20 ns
TXINF
System Clock 
Fall Time
3
3
ns
VDD = 3.0–3.6 V;
TCLK = 20 ns
CIN
Input capacitance
10 typical
10 typical
pF
Table 237 lists simulated inductance, capacitance, and resistance results for the 144-pin
LQFP package at 100 MHz operating frequency.
Table 237. Typical 144-LQFP Package Electrical Characteristics
Lead
Note:
PS019215-0910
Inductance (nH)
Capacitance (pF)
Resistance (mohm)
Longest
6.430
1.100
62.9
Shortest
4.230
1.070
52.6
Package vendor-supplied; 100 MHz operating frequency
Electrical Characteristics
eZ80F91 MCU
Product Specification
346
External Memory Read Timing
Figure 68 and Table 238 display the timing for external memory reads.
TCLK
PHI
T1
T2
ADDR[23:0]
T3
T4
DATA[7:0]
(input)
T5
T6
CSx
T7
T8
T9
T10
MREQ
RD
Figure 68. External Memory Read Timing
Table 238. External Memory Read Timing
Delay (ns)
Parameter
Abbreviation
Minimum
Maximum
T1
PHI Clock Rise to ADDR Valid Delay
—
8.5
T2
PHI Clock Rise to ADDR Hold Time
1.0
—
T3
DATA Valid to PHI Clock Rise Setup Time
0.5
—
T4
PHI Clock Rise to DATA Hold Time
0.5
—
T5
PHI Clock Rise to CSx Assertion Delay
2.6
8.0
T6
PHI Clock Rise to CSx Deassertion Delay
0.0
6.0
T7
PHI Clock Rise to MREQ Assertion Delay
2.6
7.0
T8
PHI Clock Rise to MREQ Deassertion Delay
1.0
6.3
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
347
Table 238. External Memory Read Timing (Continued)
Delay (ns)
Parameter
Abbreviation
Minimum
Maximum
T9
PHI Clock Rise to RD Assertion Delay
2.7
7.0
T10
PHI Clock Rise to RD Deassertion Delay
1.0
6.3
External Memory Write Timing
Figure 69 and Table 239 on page 348 display the timing for external memory Writes.
TCLK
PHI
T2
T1
ADDR[23:0]
T4
T3
DATA[7:0]
(output)
T5
T6
CSx
T7
T8
MREQ
T9
T10
WR
Figure 69. External Memory Write Timing
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
348
Table 239. External Memory Write Timing
Delay (ns)
Parameter
Abbreviation
Minimum
Maximum
T1
PHI Clock Rise to ADDR Valid Delay
—
8.5
T2
PHI Clock Rise to ADDR Hold Time
1
—
T3
PHI Clock Fall to DATA Valid
—
2.5
T4
PHI Clock Rise to DATA Hold Time
1.0
—
T5
PHI Clock Rise to CSx Assertion Delay
2.3
10.8
T6
PHI Clock Rise to CSx Deassertion Delay
0.0
6.0
T7
PHI Clock Rise to MREQ Assertion Delay
2.3
7.0
T8
PHI Clock Rise to MREQ Deassertion Delay
2.3
6.5
T9
PHI Clock Fall to WR Assertion Delay
—
1.0
T10
PHI Clock Rise to WR Deassertion Delay*
0.0
5.0
WR Deassertion to ADDR Hold Time
0.4
—
WR Deassertion to DATA Hold Time
0.5
—
WR Deassertion to CSx Hold Time
1.2
—
WR Deassertion to MREQ Hold Time
0.5
—
*At the conclusion of a Write cycle, deassertion of WR always occurs before any change to
ADDR, DATA, CSx, or MREQ.
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
349
External I/O Read Timing
Figure 70 and Table 240 display the timing for external I/O reads. PHI clock rise/fall to
signal transition timing is independent of the particular bus mode employed (eZ80®,
Z80®, Intel, or Motorola).
TCLK
PHI
T1
T2
ADDR[23:0]
T3
T4
DATA[7:0]
(input)
T5
T6
CSx
T7
T8
T9
T10
IORQ
RD
Figure 70. External I/O Read Timing
Table 240. External I/O Read Timing
Delay (ns)
Parameter
Abbreviation
Minimum
Maximum
T1
PHI Clock Rise to ADDR Valid Delay
—
7.3
T2
PHI Clock Rise to ADDR Hold Time
1.0
—
T3
DATA Valid to PHI Clock Rise Setup Time
0.5
—
T4
PHI Clock Rise to DATA Hold Time
0.0
—
T5
PHI Clock Rise to CSx Assertion Delay
2.0
8.5
T6
PHI Clock Rise to CSx Deassertion Delay
0.0
6.0
T7
PHI Clock Rise to IORQ Assertion Delay
2.6
7.0
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
350
Table 240. External I/O Read Timing (Continued)
Delay (ns)
Parameter
Abbreviation
Minimum
Maximum
T8
PHI Clock Rise to IORQ Deassertion Delay
1.0
6.3
T9
PHI Clock Rise to RD Assertion Delay
2.7
7.0
T10
PHI Clock Rise to RD Deassertion Delay
0.5
6.3
External I/O Write Timing
Figure 71 and Table 241 on page 351 display the timing for external I/O Writes. PHI clock
rise/fall to signal transition timing is independent of the particular bus mode employed
(eZ80®, Z80®, Intel, or Motorola).
TCLK
PHI
T2
T1
ADDR[23:0]
T4
T3
DATA[7:0]
(output)
T5
T6
CSx
T7
T8
IORQ
T9
T10
WR
Figure 71. External I/O Write Timing
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
351
Table 241. External I/O Write Timing
Delay (ns)
Parameter
Abbreviation
Min
Max
T1
PHI Clock Rise to ADDR Valid Delay
—
7.3
T2
PHI Clock Rise to ADDR Hold Time
1.0
—
T3
PHI Clock Fall to DATA Valid
—
2.5
T4
PHI Clock Rise to DATA Hold Time
1.0
—
T5
PHI Clock Rise to CSx Assertion Delay
2.3
10.8
T6
PHI Clock Rise to CSx Deassertion Delay
1.0
6.0
T7
PHI Clock Rise to IORQ Assertion Delay
2.4
7.0
T8
PHI Clock Rise to IORQ Deassertion Delay
1.0
6.3
T9
PHI Clock Fall to WR Assertion Delay
—
1.0
T10
PHI Clock Rise to WR Deassertion Delay*
0.0
5.0
WR Deassertion to ADDR Hold Time
0.4
—
WR Deassertion to DATA Hold Time
0.5
—
WR Deassertion to CSx Hold Time
1.2
—
WR Deassertion to IORQ Hold Time
0.5
—
*At the conclusion of a Write cycle, deassertion of WR always occurs before any change to ADDR,
DATA, CSx, or IORQ.
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
352
Wait State Timing for Read Operations
Figure 72 displays the extension of the memory access signals using a single Wait state for
a Read operation. This Wait state is generated by setting CS_WAIT to 001 in the Chip
Select Control Register.
TCLK
TWAIT
SCLK
ADDR[23:0]
DATA[7:0]
(output)
CSx
MREQ
RD
INSTRD
Figure 72. Wait State Timing for Read Operations
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
353
Wait State Timing for Write Operations
Figure 73 displays the extension of the memory access signals using a single Wait state for
a Write operation. This Wait state is generated by setting CS_WAIT to 001 in the Chip
Select Control Register.
TCLK
TWAIT
PHI
ADDR[23:0]
DATA[7:0]
(output)
CSx
MREQ
WR
Figure 73. Wait State Timing for Write Operations
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
354
General-Purpose Input/Output Port Input Sample Timing
Figure 74 displays timing of the GPIO input sampling. The input value on a GPIO port pin
is sampled on the rising edge of the system clock. The port value is then available to the
CPU on the second rising clock edge following the change of the port value.
TCLK
PHI
Port Value
Changes to 0
GPIO Pin
Input Value
GPIO Input
Data Latch
0 Latched
Into GPIO
Data Register
GPIO Data Register
Value 0 Read
by eZ80
GPIO Data
READ on Data Bus
Figure 74. Port Input Sample Timing
General-Purpose I/O Port Output Timing
Figure 75 and Table 242 on page 355 display timing information for GPIO port pins.
TCLK
PHI
Port Output
T1
T2
Figure 75. GPIO Port Output Timing
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
355
Table 242. GPIO Port Output Timing
Delay (ns)
Parameter
Abbreviation
Minimum
Maximum
T1
PHI Clock Rise to Port Output Valid Delay
—
5
T2
PHI Clock Rise to Port Output Hold Time
1.0
—
External Bus Acknowledge Timing
Table 243 lists information on the bus acknowledge timing.
Table 243. Bus Acknowledge Timing
Delay (ns)
Parameter
Abbreviation
T1
PHI Clock Rise to BUSACK Assertion Delay
2.8
7.1
T2
PHI Clock Rise to BUSACK Deassertion Delay
1.5
6.5
PS019215-0910
Minimum Maximum
Electrical Characteristics
eZ80F91 MCU
Product Specification
356
PS019215-0910
Electrical Characteristics
eZ80F91 MCU
Product Specification
357
Packaging
Figure 76 displays the 144-pin low-profile quad flat package (LQFP) for the eZ80F91
device.
HD
D
A
A2
A1
CL
F
E
HE
DETAIL A
CL
LE
c
b
e
L
Figure 76. 144-Lead Plastic Low-Profile Quad Flat Package (LQFP)
PS019215-0910
Packaging
eZ80F91 MCU
Product Specification
358
Figure 77 displays the 144-pin chip array ball grid array (BGA) package for the eZ80F91
device.
Figure 77. 144-Lead Chip Array Ball Grid Array (BGA)
PS019215-0910
Packaging
eZ80F91 MCU
Product Specification
359
Ordering Information
Table 244 lists part name, a product specification index code, and a brief description of
each part. Order the eZ80F91 microcontroller from Zilog®, using the following part numbers. For more information on ordering, please consult your local Zilog sales office. The
Zilog website (www.zilog.com) lists all regional offices and provides additional eZ80F91
microcontroller product information.
Table 244. Ordering Information
Part
PSI
Description
eZ80F91
eZ80F91AZ050SG*
144-pin LQFP, 256 KB Flash memory, 8 KB SRAM, 50 MHz,
Standard Temperature
eZ80F91AZ050EG*
144-pin LQFP, 256 KB Flash memory, 8 KB SRAM, 50 MHz,
Extended Temperature
eZ80F91NA050SG*
144-pin BGA, 256 KB Flash memory, 8 KB SRAM, 50 MHz,
Standard Temperature
eZ80F91NA050EG*
144-pin BGA, 256 KB Flash memory, 8 KB SRAM, 50 MHz,
Extended Temperature
eZ80F910200ZC0G
eZ80F91 Acclaim! Development Kit
eZ80F910100KITG
eZ80F91 Acclaim! Modular Development Kit
eZ80F9105050MODG
Ethernet Module
eZ80F9105005MODG
Mini Ethernet Module
ZUSBSC00100ZACG
USB Smart Cable
ZENETSC0100ZACG
Ethernet Smart Cable
*Denotes parts not recommended for new designs.
PS019215-0910
Ordering Information
eZ80F91 MCU
Product Specification
360
Part Number Description
Zilog® part numbers consists of number of components as described below:
eZ80 F91 AZ 050
S
C
Environmental Flow
C = Plastic Standard
G = Lead-Free
Temperature Range
S = Standard, 0 °C to 70 °C
E = Extended, –40 °C to +105 °C
Speed
0 = eZ80Acclaim!
50 = Speed
Package
AZ = LQFP (also called VQFP)
NA = BGA
Product Number
Zilog eZ80® CPU
Example: Part number eZ80F91AZ050SC is an eZ80F91 Acclaim! product in a LQFP
package, operating with a 50 MHz external clock frequency over a 0 ºC to +70 ºC temperature range and built using the Plastic Standard environmental flow.
PS019215-0910
Ordering Information
eZ80F91 MCU
Product Specification
361
Index
Numerics
100-pin LQFP package 4, 5
16-bit clock divisor value 182, 206
16-bit divisor count 182, 206
32 KHz Real-Time Clock Crystal Oscillator Operation 337
A
AAK 217, 218, 220, 221, 222, 226, 227
Absolute Maximum Ratings 339
Absolute maximum ratings 339
AC Characteristics 344
ACK 213, 217, 218, 219, 220, 221, 223, 228
Acknowledge 213
Acknowledge, I2C 213
ADDR0 6
ADDR1 6
ADDR10 6
ADDR11 6
ADDR12 7
ADDR13 7
ADDR14 7
ADDR15 7
ADDR16 7
ADDR17 7
ADDR18 7
ADDR19 7
ADDR2 6
ADDR20 7
ADDR21 7
ADDR22 7
ADDR23 7
ADDR3 6
ADDR4 6
ADDR5 6
ADDR6 6
ADDR7 6
ADDR8 6
ADDR9 6
PS019215-0910
Address Bus 6, 7
address bus 58, 68, 70, 71, 74, 75, 78, 81, 82,
85, 86, 161, 238, 239, 249, 255
address bus, 24-bit 27
Addressing, I2C 223
ALARM 160, 174
ALARM bit flag 173
alarm condition 160, 161, 173, 174
AND/OR Gating of the PWM Outputs 148, 149
Arbiter, EMAC 289
Arbitration, I2C 215
asynchronous communications protocol 175, 176
asynchronous communications protocol bits 176
asynchronous serial data 11, 14
B
Basic Timer Operation 122
Basic Timer Register Set 130
Baud Rate Generator 181
Baud Rate Generator Functional Description 205
BCD 159, 173, 174
Binary Operation 161, 162, 163, 166, 167, 168,
169, 170, 171, 172
binary operation 159
binary-coded-decimal 159
Binary-Coded-Decimal Operation 161, 164, 165,
166, 167, 168, 169, 170, 171, 172
bit generation 175, 176
Block Diagram 2
Boot Block 25, 97, 107, 109
Boundary Scan Cell Functionality 260
Boundary Scan Instructions 264
Boundary-Scan Architecture 257
break detection 175, 185
Break Point Halting 126
break point trigger functions 257
BRG Control Registers 182
Bus Acknowledge Cycle 70
bus acknowledge cycle 6, 8, 9, 89, 90, 91, 94
bus acknowledge pin 70, 249
Bus Arbiter 89
Bus Arbitration Overview 211
Bus Clock Speed, I2C 230
Index
eZ80F91 MCU
Product Specification
362
Bus Mode Controller 70
bus mode state 71, 72, 75
Bus modes 70
bus modes 71, 84, 88
Bus Modes, Switching Between 84
Bus Requests During ZDI Debug Mode 238
bus timing 70
BUSACK 9, 70, 239, 249, 255, 355
BUSACK pin 89, 249, 255
BUSREQ 9, 70, 255
BUSREQ pin 89, 239, 249, 255
Byte Format, I2C 213
C
C source-level debugging 231
capture flag 128
Carrier Sense 307
carrier sense 303
carrier sense window 308
Carrier Sense Window Referencing 308
Carrier Sense, MII 22
Chain Sequence and Length, JTAG Boundary Scan
260
Characteristics, electrical
Absolute maximum ratings 339
Charge Pump 265
charge pump 269
Charge Pump, PLL 266
Chip Select Registers 85
Chip Select x Bus Mode Control Register 88
Chip Select x Control Register 87
Chip Select x Lower Bound Register 85
Chip Select x Upper Bound Register 86
Chip Select/Wait State Generator block 6
Chip Selects During Bus Request/Bus Acknowledge Cycles 70
Clear to Send 12, 15, 193
CLK_MUX 269
clock divisor value, 16-bit 182, 206
clock initialization circuitry 258
Clock Peripheral Power-Down Registers 46
clock phase 202
clock phase bit 204
PS019215-0910
clock polarity bit 204
Clock Synchronization for Handshake 216
Clock Synchronization, I2C 214
Clocking Overview 211
COL 22
Complex triggers 257
CONTINUOUS mode 125
Continuous Mode 123, 126
continuous mode 121, 132, 138, 139
Control Transfers, UART 179
CPHA—see clock phase 202, 203, 208
CPOL—see clock polarity 203, 208
CRC 294, 295, 299, 300, 312
CRS 22, 307
CS0 7, 65, 66, 67, 68
CS1 7, 65, 66, 67, 68
CS2 7, 65, 67, 68
CS3 7, 65, 67, 68
CTS 191, 193
CTS0 12, 198
CTS1 15
Customer Feedback Form 375
D
DATA bus 78
Data Bus 8
data bus 70, 71, 73, 74, 75, 82, 88, 161, 238,
239, 249, 255
Data Carrier Detect 13, 16, 193
Data Set Ready 13, 16, 193
Data Terminal Ready 12, 15, 191
Data Transfer Procedure with SPI configured as a
Slave 206
Data Transfer Procedure with SPI Configured as the
Master 205
data transfer, SPI 209
Data Transfers, UART 179
Data Validity, I2C 212
DATA0 8
DATA1 8
DATA2 8
DATA3 8
DATA4 8
Index
eZ80F91 MCU
Product Specification
363
DATA5 8
DATA6 8
DATA7 8
DC Characteristics 339
DCD 190, 193
DCD0 13, 198
DCD1 16
DCTS 193
DDCD 193
DDSR 193
Divider, PLL 266
divisor count 206
divisor count, 16-bit 182
DSR 191, 193
DSR0 13, 198
DSR1 16
DTACK 81, 82
DTR 191, 193
DTR0 12, 198
DTR1 15
E
EC0 17, 127, 129, 132
EC1 22, 127, 129, 132
edge-selectable interrupts 55
Edge-Triggered Interrupts 54
EI, Op Code Map 280
EMAC 287
EMAC Address Filter Register 311
EMAC Boundary Pointer Register—Low and High
Bytes 319
EMAC Boundary Pointer Register—Upper Byte
319
EMAC Buffer Size Register 322
EMAC Configuration Register 1 299
EMAC Configuration Register 2 301
EMAC Configuration Register 3 302
EMAC Configuration Register 4 303
EMAC FIFO Data Register—Low and High Bytes
332
EMAC FIFO Flags Register 333
EMAC Functional Description 288
EMAC Hash Table Register 312
PS019215-0910
EMAC Interpacket Gap 306
EMAC Interpacket Gap Overview 306
EMAC Interpacket Gap Register 307
EMAC Interrupt Enable Register 323
EMAC Interrupt Status Register 325
EMAC Interrupts 292
EMAC Maximum Frame Length Register—Low
and High Bytes 309
EMAC memory 288, 289
EMAC MII Management Register 313
EMAC MII Status Register 327
EMAC Non-Back-To-Back IPG Register—Part 1
308
EMAC Non-Back-To-Back IPG Register—Part 2
308
EMAC PHY Address Register 315
EMAC PHY Configuration Data Register—Low
Byte 314
EMAC PHY Read Status Data Register—Low and
High Bytes 326
EMAC PHY Unit Select Address Register 316
EMAC RAM 93, 94, 95, 96
EMAC Receive Blocks Left Register—Low and
High Bytes 330
EMAC Receive High Boundary Pointer Register—
Low and High Bytes 320
EMAC Receive Read Pointer Register—Low and
High Bytes 321
EMAC Receive Write Pointer Register—High Byte
329
EMAC Receive Write Pointer Register—Low Byte
328
EMAC Receiver Interrupts 292
EMAC Registers 297
EMAC Reset Control Register 317
EMAC Shared Memory Organization 292
EMAC Station Address Register 304
EMAC System Interrupts 292
EMAC Test Register 298
EMAC Transmit Lower Boundary Pointer Register—Low and High Bytes 318
EMAC Transmit Pause Timer Value Register—
Low and High Bytes 305
EMAC Transmit Polling Timer Register 316
Index
eZ80F91 MCU
Product Specification
364
EMAC Transmit Read Pointer Register—High
Byte 330
EMAC Transmit Read Pointer Register—Low Byte
329
EMAC Transmitter Interrupts 292
EMACMII module 287
Enabling and Disabling the WDT 116
Endec 199
endec 195, 196, 198
ENDEC Mode 306
ENDEC mode 302
endec signal pins 198
endec, IrDA 47
Erasing Flash Memory 101
Ethernet Media Access Controller 287
event count input 132
Event count mode 127
event count mode 128
Event Counter 125, 127
event counter 127
External Bus Acknowledge Timing 355
external bus master 89, 90
external bus request 70, 235, 239
External I/O Read Timing 349
External I/O Write Timing 350
External Memory Read Timing 346
External Memory Write Timing 347
external pull-down resistor 51
External Reset Input and Indicator 41
eZ80 Bus Mode 71
eZ80 bus mode 88
eZ80 CPU 8, 69, 70, 74, 81, 195, 241, 257
eZ80 Product ID Low and High Byte Registers 251
eZ80 Product ID Revision Register 252
eZ80 Webserver-i 2, 6, 8, 9, 19, 57, 58, 68, 115
eZ80 Webserver-i Block Diagram 3
eZ80Acclaim! Flash Microcontrollers 1, 98
eZ80F91 device 4, 5, 27, 340
eZ80F92 252
F
f 71, 74, 346
falling edge 147, 148, 150, 155
PS019215-0910
FAST mode 211, 230
FCS 295, 296, 306
Features 1
Features, eZ80 CPU Core 39
FIFO mode 176, 179
Flash Address registers 100, 103, 110
Flash address registers 99
Flash Address Upper Byte Register 104
Flash Column Select Register 112
Flash Control Register 105
Flash Control Registers 102
Flash controller 98, 99, 100, 106, 108
Flash controller clock 106
Flash Data Register 103
Flash Frequency Divider Register 106
Flash Interrupt Control Register 108
Flash Key Register 102
Flash Memory 97
Flash memory array 98, 109
Flash Memory Overview 98
Flash Page Select Register 109
Flash Program Control Register 112
Flash Row Select Register 111
Flash Write/Erase Protection Register 107
frame check sequence 306
framing error 175, 177, 185, 192
frequency divider 98, 106
full-duplex transmission 204
Functional Description, Infrared Encoder/Decoder
195
Functional Description, Serial Peripheral Interface
204
G
General-Purpose I/O Port Input Sample Timing
354
General-Purpose I/O Port Output Timing 354
General-Purpose Input/Output 49
GND 2
GPIO Control Registers 55
GPIO Interrupts 54
GPIO modes 50, 52
GPIO Operation 49
Index
eZ80F91 MCU
Product Specification
365
GPIO Overview 49
GPIO port pins 41, 49, 55, 354
H
HALT 10, 253, 277
HALT instruction 45
HALT Mode 45
HALT mode 1, 46, 245, 253
HALT, Op-Code Map 280
HALT_SLP 10, 253, 260
Handshake 216
handshake 175, 177
hash table 311
I
I/O Chip Select Operation 68
I/O Chip Selects, External 27
I/O Read 99
I/O space 6, 8, 65, 68
I2C Acknowledge bit 226
I2C bus 211, 214, 215
I2C bus clock 211
I2C bus protocol 212
I2C Clock Control Register 229
I2C control bit 217, 218, 220
I2C Control Register 225
I2C Data Register 225
I2C Extended Slave Address Register 224
I2C Registers 223
I2C Software Reset Register 230
I2C Status Register 227
IC0 17, 127, 129, 134, 135, 139, 140, 141, 142,
152, 156
IC1 17, 127, 129, 134, 135, 139, 141, 152, 156
IC2 18, 127, 129, 134, 135, 139, 140, 141, 152,
156
IC3 18, 127, 129, 134, 135, 139, 141, 142, 152,
156
IEEE 1149.1 specification 259, 264
IEEE 802.3 311
IEEE 802.3 frames 300
IEEE 802.3 specification 301, 302
PS019215-0910
IEEE 802.3, 802.3(u) minimum values 306
IEEE 802.3/4.2.3.2.1 Carrier Deference 307, 308
IEEE Standard 1149.1 257, 258
IEF1 59, 125, 253
IEF2 59
IFLG bit 211, 216, 219, 221, 222, 223, 226, 229
IM 0, Op Code Map 283
IM 1, Op Code Map 283
IM 2, Op Code Map 283
Information Page Characteristics 102
Infrared Encoder/Decoder 195
Infrared Encoder/Decoder Register 199
Infrared Encoder/Decoder Signal Pins 198
Input Capture 128
INPUT capture mode 130
Input capture mode 128
input capture mode 127, 134
INSTRD 9
Instruction Store 4
0 Registers 249
Intel- 70
Intel Bus Mode 73
Intel Bus Mode (Separate Address and Data Buses)
74
internal pull-up 50
Internal RC oscillator 115
internal RC oscillator 118
internal system clock 69
Interpacket Gap 306, 307
Interpacket gap 306
interpacket gap 296, 308
Interrupt Controller 57
interrupt enable 9
Interrupt Enable bit 225
interrupt enable bit 160, 178
Interrupt Enable Flag 253
interrupt enable flag 125
Interrupt Input 198
interrupt input 11, 12, 13, 14, 15, 16
Interrupt Priority 61, 63
interrupt priority 63
interrupt priority levels 60
Interrupt Priority Registers 60
Interrupt request 133, 134
Index
eZ80F91 MCU
Product Specification
366
interrupt request 54, 58, 108, 127
interrupt request signals 57
interrupt service routine 58, 59, 60
interrupt service routine, SPI 58
interrupt sources 152
interrupt vector 57, 58
interrupt vector address 59, 60
interrupt vector bus 58
interrupt vector locations 58
interrupt vector table 58
interrupt, higher-priority 62, 186
interrupt, highest-priority 57, 58
interrupts, edge-selectable 55
interrupts, level-sensitive 55
Introduction to On-Chip Instrumentation 257
Introduction, Zilog Debug Interface 231
IORQ 8, 9, 68, 71, 74, 75, 78
IORQ Assertion Delay 349, 351
IORQ Deassertion Delay 350, 351
IORQ Hold Time 351
IR_RXD 196, 198, 199
IR_TxD modulation signal 11, 196, 198
IrDA Encoder/Decoder 198
IrDA encoder/decoder 11
IrDA endec 47
IrDA Receive Data 11
IrDA specifications 196
IrDA standard 195
IrDA standard baud rates 195
IrDA transceiver 198
IrDA Transmit Data 11
IrDA—see Infrared Data Association 195
IRQ 58
irq_en 205, 208
ISR 58
IVECT 57, 58, 59, 60
J
Jitter, Infrared Encoder/Decoder 198
JTAG Boundary Scan 259
JTAG interface 257, 264
JTAG mode selection 258
JTAG Test Mode 10
PS019215-0910
L
least-significant byte 58
level-sensitive interrupt modes 52
level-sensitive interrupts 55, 198
Level-Triggered Interrupts 54
Line break detection 175
line status error 178
Line status interrupt 185
line status interrupt 177, 179, 180
Lock Detect 265
lock detect 267
lock detect sensitivity 269
Lock Detect, PLL 266
Loop Filter 265
loop filter 267, 273
Loop Filter, PLL 13, 266
loop mode 177
LOOP_FILT 259
Loopback Testing, Infrared Encoder/Decoder 198
low-byte vector 57
LSB 59, 60, 138, 229, 304, 311
Lsb 291
lsb 136, 138, 140, 141, 144, 157, 158, 216,
217, 218, 219, 220, 222, 310, 314, 318, 320,
321, 326, 328, 329
M
maskable interrupt 46, 57, 60, 62
Maskable Interrupts 57
Mass Erase 101
mass erase 107, 108, 112
MASS ERASE operation 102
Mass Erase operation 113
mass erase operation 101, 110
MASTER mode 203, 211, 226, 228, 229, 230
Master mode 222, 227
master mode 222
Master Mode Start bit 225
Master Mode Stop bit 226
MASTER mode, SPI 204
Master Receive 211, 219
Master Transmit 216
MASTER TRANSMIT mode 211
Index
eZ80F91 MCU
Product Specification
367
master_en bit 204
Master-In, Slave-Out 202
Master-Out, Slave-In 202
MAXF 299
MAXF—see Maximum Frame Length 309
Maximum Frame Length 309
MBIST 96
MBIST Control 96
MDC 24, 314
MDIO 25
Memory and I/O Chip Selects 65
Memory Built-In Self-Test controllers 96
Memory Chip Select Example 66
Memory Chip Select Operation 65
Memory Chip Select Priority 66
Memory Read 99
Memory Request 8
memory space 65, 68
Memory Write 101
Memory, EMAC 288
MII 287, 292, 306, 313, 324, 325, 326, 327
MISO—see SPI Master In Slave Out 19, 202, 204
mode fault 209
Mode Fault error flag 202
Mode Fault flag 204
Mode Fault, SPI Flag 204
Modem Status 186, 193
Modem status 178
modem status 179, 180, 190
modem status interrupt 198
Modem status signal 12, 13, 15, 16
MODF 202, 204, 209
Module Reset, UART 179
MOSI—see SPI Master Out Slave In 19, 202, 203,
204
Motorola Bus Mode 80
Motorola-compatible 70
mpwm_en 146, 153
MREQ 8, 9, 65, 71, 74, 75, 78, 346, 348
MREQ Hold Time 348
MSB 58, 139
Msb 291
msb 109, 137, 139, 141, 142, 145, 157, 158,
213, 237, 310, 318, 327, 329, 330, 331
PS019215-0910
Multibyte I/O Write (Row Programming) 100
multicast address 296, 312
multicast packet 311, 312
multimaster conflict 204, 209
Multi-PWM Control Registers 153
Multi-PWM Mode 145
Multi-PWM Power-Trip Mode 152
Mux/CLK Sync 265
MUX/CLK Sync, PLL 266
N
NACK 213, 217, 218, 220, 221, 226, 228
New Instructions, eZ80 CPU Core 39
NMI 9, 39, 46, 57, 115, 116, 117
NMI_flag bit 117
nmi_out bit 116
Nonmaskable Interrupt 9, 39
Nonmaskable interrupt 278
nonmaskable interrupt 46, 57, 115, 116
nonoverlapping delay, PWM 148, 151
Not Acknowledge 213
O
OC0 20, 127, 129, 133, 135, 143, 144, 145
OC1 20, 127, 129, 133, 135
OC2 20, 127, 129, 133, 135
OC3 21, 127, 129, 133, 135, 144, 145
OCI Activation 258
OCI clock pin 258
OCI Interface 258
On-Chip Instrumentation, Introduction to 257
on-chip pull-up 340, 359
On-chip RAM 65, 93, 94
Op Code maps 280
Op-Code Map 280
Open source I/O 50
Open-drain I/O 50
open-drain I/O 50
open-drain mode 50
Open-drain output 50
open-drain output 211
open-source mode 51
Index
eZ80F91 MCU
Product Specification
368
Open-source output 50
open-source output 11, 12, 13, 14, 15, 16, 17, 18,
19
Operating Modes, I2C 216
Operation of the eZ80F91 Device during ZDI Break
Points 238
Ordering Information 358
Output Compare 128
Output compare mode 143
output compare mode 127, 128, 130, 133
overrun condition, receiver 178
Overrun error 192
overrun error 175, 177, 185
Overview, Phase-Locked Loop 265
P
PA7 150
Packaging 357
Page Erase 101
page erase 112
Page Erase operation 113
page erase operation 101, 109
PAIR_EN 153, 154
parity error 177, 188, 192
Part Number Description 360
PB0 17
PB1 17
PB2 17
PB3 18
PB4 18
PB5 18
PB6 19
PB7 19
PC0 14, 20
PC1 14, 20
PC2 15, 20
PC3 15, 21
PC4 15, 21
PC5 16, 21
PC6 16, 22
PC7 16, 22
PD0 11, 198
PD1 11, 198
PS019215-0910
PD2 12, 198
PD3 12
PD4 12
PD5 13
PD6 13
PD7 13, 198
Phase Frequency Detector 265
Phase Frequency Detector, PLL 266
PHI 19, 261
PHI Clock output 48
PHY 22, 24, 28, 29, 292, 296, 314, 315, 325,
326, 327
PHY, MII 288, 313
Pin Characteristics 6
Pin Coverage, JTAG Boundary Scan 259
Pin Description 4
PLL Characteristics 272
PLL Control Register 0 269
PLL Control Register 1 270
PLL Divider Control Register—Low and High
Bytes 268
PLL Loop Filter 13
PLL Normal Operation 267
PLL Registers 268
PLL_VDD 268
PLL_VSS 268
Poll Mode Transfers 181
POP, Op Code Map 280, 282, 284
POR Voltage Threshold 341
POR voltage threshold 42
POR/VBO analog RESET duration 341
POR/VBO DC current consumption 341
POR/VBO Hysteresis 341
Port A 20, 21, 47, 49, 58, 62, 63, 145
Port x Alternate Register 1 56
Port x Alternate Register 2 56
Port x Data Direction Registers 55
Port x Data Registers 55
Potential Hazards of Enabling Bus Requests During
Debug Mode 239
Power connections 2
Power Requirement to the Phase-Locked Loop
Function 268
Power-On Reset 41, 42, 340
Index
eZ80F91 MCU
Product Specification
369
power-trip 153
Power-Trip Mode, Multi-PWM 152
power-trip, multi-PWM 152
Primary Crystal Oscillator Operation 335
Program Counter 41, 45, 46, 59, 97, 250, 251,
255
Program Counter, Starting 60
Programmable Reload Timers 121
Programming Flash Memory 99
Promiscuous Mode 311
PT_EN 153
pull-up resistor, external 51, 211
Pulse-Width Modulation Control Register 1 153
Pulse-Width Modulation Control Register 2 154
Pulse-Width Modulation Control Register 3 156
Pulse-Width Modulation Falling Edge—High Byte
158
Pulse-Width Modulation Falling Edge—Low Byte
158
Pulse-Width Modulation Rising Edge—High Byte
157
Pulse-Width Modulation Rising Edge—Low Byte
157
PUSH, Op Code Map 280, 282, 284
PWM delay feature 151
PWM edge transition values 148, 149
PWM generator 145, 146, 147, 148, 153
PWM generators 146
PWM Master Mode 148
PWM mode 121, 127, 130, 131, 134
PWM mode, Multi- 145, 146, 148, 149, 153
PWM nonoverlapping delay 148
PWM nonoverlapping delay time 151
PWM Nonoverlapping Output Pair Delays 150
PWM output pairs 148
PWM outputs 149, 150, 152
PWM Outputs, AND/OR Gating 148, 149
PWM outputs, inverted 147
PWM pairs 149
PWM power-trip state 152
PWM signals 145
PWM trip levels 156
PWM waveform 149
PWM0 150
PS019215-0910
PWM1 20, 21, 127, 129, 147, 149
PWM1 falling edge end-of-count 148, 151
PWM1 rising edge end-of-count 148, 151
pwm1_en 153
PWM1FH 148
PWM1RH 157, 158
PWM1RL 157, 158
PWM2 20, 22, 127, 129, 147
PWM2 falling edge end-of-count 148
PWM2 rising edge end-of-count 148
pwm2_en 153
PWM2RH 148
PWM3 21, 22, 127, 147
pwm3_en 153
PWMCNTRL1 146
PWMCNTRL2 148
PWMCNTRL3 152
Q
QMC 311
qualified multicast messages 311
R
RAM 93
RAM Address Upper Byte Register 95
RAM Control Register 94
Random Access Memory 93
RD 8, 65, 68, 71, 74, 75, 78
RD Assertion Delay 347, 350
RD Deassertion Delay 347, 350
Reading Flash Memory 98
Reading the Current Count Value 122
Real-Time Clock 41, 45, 159, 160, 161, 173
Real-Time Clock Alarm 160
Real-Time Clock alarm 45
Real-Time Clock Alarm Control Register 173
Real-Time Clock Alarm Day-of-the-Week Register
172
Real-Time Clock Alarm Hours Register 171
Real-Time Clock Alarm Minutes Register 170
Real-Time Clock Alarm Seconds Register 169
Real-Time Clock Battery Backup 160
Index
eZ80F91 MCU
Product Specification
370
Real-Time Clock Century Register 168
Real-Time Clock Control Register 173
Real-Time Clock Day-of-the-Month Register 165
Real-Time Clock Day-of-the-Week Register 164
Real-Time Clock Hours Register 163
Real-Time Clock Minutes Register 162
Real-Time Clock Month Register 166
Real-Time Clock Oscillator and Source Selection
160
Real-Time Clock Overview 159
Real-Time Clock Recommended Operation 160
Real-Time Clock Registers 161
Real-Time Clock Seconds Register 161
Real-Time Clock signal 128
Real-Time Clock source 115, 118, 125
Real-Time Clock Year Register 167
Receive, Infrared Encoder/Decoder 196
Recommended Usage of the Baud Rate Generator
181
Register Set for Capture in Timer 1 130
Register Set for Capture/Compare/PWM in Timer 3
130
Request to Send 12, 15, 191
RESET 9, 41, 42, 45, 46, 50, 65, 93, 94, 105,
107, 115, 116, 161, 164, 165, 166, 167, 168,
169, 170, 171, 172, 173, 174, 181, 182, 199,
205, 206, 243, 245, 258, 260, 341
Reset controller 41, 42
RESET event 41, 49
RESET mode timer 41, 42
RESET Or NMI Generation 116
Reset States 66
RESET_OUT 260
Resetting the I2C Registers 223
RI 177, 191, 193
RI0 13, 198
RI1 16, 51
Ring Indicator 13, 16, 193
rising edge 147, 148, 150, 155
rst_flag bit 116
RTC Oscillator Input 128
RTC Supply Voltage 340
RTC_VDD 10
RTC_XIN 10
PS019215-0910
RTC_XOUT 10
RTS 191, 193, 198
RTS0 12
RTS1 15
RX_CLK 24
Rx_CLK 23
Rx_DV 24
Rx_ER 23
RxD0 11, 24
RxD1 14, 24
RxD2 24
RxD3 24
RxDMA 290
S
Schmitt Trigger 9
Schmitt trigger 9
Schmitt Trigger Input 9, 11, 14, 15, 17, 18, 25
Schmitt-trigger input buffers 49
SCK 18, 202
SCK Idle State 203
SCK pin 204, 208
SCK Receive Edge 203
SCK signal 204
SCK Transmit Edge 203
SCL 19, 211, 212, 213, 229
SCL line 214, 216
SCLK 41, 150, 265, 314
SClk 266
Sclk 267
SCLK periods 155
SDA 19, 211, 212, 213, 222
SDA line 215
see system reset 8
serial bus, SPI 209, 210
Serial Clock 211
Serial Clock, I2C 19
Serial Clock, SPI 18, 202
Serial Data 211
serial data 202
Serial Data, I2C 19
Serial Peripheral Interface 1, 47, 58, 62, 201,
202, 204
Index
eZ80F91 MCU
Product Specification
371
Serial Peripheral Interface flag 209, 210
Serial Peripheral Interface Functional Description
204
Setting Timer Duration 122
Single Pass Mode 123
single pass mode 121, 124, 132
Single-Byte I/O Write 99
SLA 218, 220, 224, 279
SLA, Op Code Map 285, 286
SLA, Op Code map 281
SLAVE mode 211, 225, 228
slave mode 222, 223, 224
SLAVE mode, SPI 204
Slave Receive 211, 222
Slave Select 202
Slave Transmit 211, 221
Slave Transmit mode 226
slave transmit mode 221, 222
SLEEP Mode 45
SLEEP mode 173, 245, 253
sleep-mode recovery 173
sleep-mode recovery reset 174
Software break point instruction 257
Specialty Timer Modes 126
SPI Baud Rate Generator 205
SPI Baud Rate Generator Registers—Low Byte and
High Byte 206
SPI Control Register 208
SPI Data Rate 205
SPI Flag 204
SPI interrupt service routine 58
SPI Master device 206
SPI master device 19
SPI MASTER mode 204
SPI mode 17
SPI Receive Buffer Register 210
SPI Registers 206
SPI serial bus 209
SPI Serial Clock 18
SPI Signals 202
SPI slave device 19
SPI SLAVE mode 204
SPI Status Register 205, 209
SPI Transmit Shift Register 205, 206, 209
PS019215-0910
SPIF status bit—see Serial Peripheral Interface flag
209
SPIF—see Serial Peripheral Interface flag 204,
209
SRA 279
SRA, Op Code Map 281, 285
SRAM 1, 104, 231, 329, 359
SRAM, internal Ethernet 292
SS—see Slave Select 17, 202, 203, 204, 206,
208
STA 225
standard mode 211
Standard VHDL Package STD_1149_1_2001 260
START and STOP Conditions 212
START condition 212, 215, 216, 218, 219, 221,
222, 223, 225, 227, 228, 229, 230
start condition 213
Start Condition, ZDI 233
Starting Program Counter 59, 60
STOP condition 212, 213, 215, 219, 221, 222,
226, 227, 229, 230
Supply Voltage 340
supply voltage 2, 42, 50, 211, 267, 339
Switching Between Bus Modes 84
System clock 47, 48, 115
system clock 41, 45, 51, 54, 118, 125, 127, 132,
150, 181, 205, 229, 230, 238, 258, 266, 289,
354
system clock cycle 75, 78, 122
System Clock Cycle Time 344
system clock cycles 9, 68, 71, 72, 75, 78, 82,
116, 258
System clock divider 132
System Clock Fall Time 345
System Clock Frequency 122, 181, 205
system clock frequency 99, 101, 105, 106, 232
System Clock High Time 344
system clock jitter 127
System Clock Low Time 344
System Clock Oscillator Input 14
System Clock Oscillator Output 13
system clock period 258
system clock periods 151
System Clock Rise Time 345
Index
eZ80F91 MCU
Product Specification
372
system clock rising edge 181, 205
System Clock Source 269
System clock source 270
system clock source 269
system clock, high-frequency 205
system clock, internal 69
system RESET 41, 162, 163
system reset 160, 183, 267, 297
T
T2 clock 151
T2 end-of-count 151
T23CLKCN 151
TAP 264
TAP Reset 258
TCK 233, 258, 259, 264
TDI 258, 259, 260
TDO 258, 259, 260
TERI 193
Test Access Port 257
Test Access Port instruction 264
Test Access Port state register 258
Test Mode 258
Time-Out Period Selection 116
Timer Control Register 132
Timer Data Register—High Byte 137
Timer Data Register—Low Byte 136
Timer Input Capture Control Register 139
Timer Input Capture Value A Register—High Byte
141
Timer Input Capture Value A Register—Low Byte
140
Timer Input Capture Value B Register—High Byte
142
Timer Input Capture Value B Register—Low Byte
141
Timer Input Source Selection 125
Timer Interrupt Enable Register 133
Timer Interrupt Identification Register 135
Timer Interrupts 124
Timer Output 125
Timer Output Compare Control Register 1 142
Timer Output Compare Control Register 2 143
PS019215-0910
Timer Output Compare Value Register—High Byte
145
Timer Output Compare Value Register—Low Byte
144
Timer Port Pin Allocation 129
Timer Registers 130
Timer Reload Register—High Byte 139
Timer Reload Register—Low Byte 138
TMS 258, 259
TOUT0 21, 129
TOUT1 21, 129
Trace buffer memory 257
Trace history buffer 257
Transferring Data 213
transmit shift register 176, 185, 188, 191
Transmit Shift Register, SPI 204, 205, 206, 209,
210
Transmit, Infrared Encoder/Decoder 196
trigger-level detection logic 176
TRIGOUT 258, 260
tristate 152
TRSTN 258, 259
Tx_CLK 23
Tx_EN 23
Tx_ER 23
TxD0 11, 23
TxD1 14, 23
TxD2 23
TxD3 22
TxDMA 290
U
UART Baud Rate Generator Register—Low and
High Bytes 182
UART FIFO Control Register 187
UART Functional Description 176
UART Functions 176
UART Interrupt Enable Register 184
UART Interrupt Identification Register 186
UART Interrupts 178
UART Line Control Register 188
UART Line Status Register 191
UART Modem Control 177
Index
eZ80F91 MCU
Product Specification
373
UART Modem Control Register 190
UART Modem Status Interrupt 179
UART Modem Status Register 193
UART Receive Buffer Register 184
UART Receiver 177
UART Receiver Interrupts 178
UART Recommended Usage 179
UART Registers 183
UART Scratch Pad Register 194
UART Transmit Holding Register 183
UART Transmitter 176
UART Transmitter Interrupt 178
Universal Asynchronous Receiver/Transmitter 175
Usage, JTAG Boundary Scan 264
V
VBO 41, 42, 340
VBO pulse reject period 341
VBO Voltage Threshold 341
VCC 2, 42, 341
VCC ramp rate 341
VCO 266, 273
vco 273
VLAN tagged frame 309
Voltage Brown-Out 340
Voltage Brown-Out Reset 42
Voltage Controlled Oscillator 265
Voltage Controlled Oscillator, PLL 266
voltage signal, high 100
voltage, input 266
voltage, peak-to-peak 273
voltage, supply 2, 50, 211, 267, 339, 340
W
WAIT 1, 9, 75, 78, 81, 82
WAIT condition 112
WAIT Input Signal 69
WAIT pin, external 71
WAIT state 72, 78, 352, 353
Wait State Timing for Read Operations 352
Wait State Timing for Write Operations 353
WAIT states 58, 75, 78, 87, 239
PS019215-0910
Wait States 68
Watchdog Timer 1, 45, 115, 116, 238
Watchdog Timer Control Register 117
Watchdog Timer Operation 116
Watchdog Timer Registers 117
Watchdog Timer Reset Register 119
Watchdog Timer time-out 41, 45, 46
wcOl 209
WCOL—see Write Collision 204, 205
WDT 41, 45, 115, 116, 117
WDT clock source 115, 116, 118
WDT oscillator 117
WDT time-out 115, 116, 117, 119
WDT time-out period 116, 118
WP 25
WP pin 97, 107, 108, 109
WR 8, 65, 68, 71, 75, 78, 348, 351
Write Collision 205
write collision 204
write collision, SPI 209
X
XIN input pin 335
XOUT output pin 335
Z
Z80- 70
Z80 Bus Mode 71
ZCL 233, 236, 243
ZDA 233, 243, 258
ZDI 231, 232, 257
ZDI Address Match Registers 241
ZDI Block Read 238
ZDI Block Write 236
ZDI Break Control Register 242
ZDI Bus Control Register 249
ZDI Bus Status Register 255
ZDI Clock and Data Conventions 233
ZDI clock pin 233
ZDI data pin 233
ZDI debug control 257
ZDI Master Control Register 245
Index
eZ80F91 MCU
Product Specification
374
ZDI Read Memory Register 255
ZDI Read Operations 237
ZDI Read Register Low, High, and Upper 254
ZDI Read/Write Control Register 247
ZDI Read-Only Registers 240
ZDI Register Addressing 235
ZDI Register Definitions 241
ZDI Single-Bit Byte Separator 234
ZDI Single-Byte Read 237
ZDI Single-Byte Write 236
ZDI Start Condition 233
ZDI Status Register 253
ZDI Write Data Registers 246
ZDI Write Memory Register 250
ZDI Write Only Registers 239
ZDI Write Operations 236
ZDI_BUS_STAT 239, 241, 255
ZDI_BUSACK_EN 238
ZDI_BUSAcK_En 255
ZDI-Supported Protocol 232
ZDS II 231
Zilog Debug Interface 231, 257
Zilog Developer Studio II 231
PS019215-0910
Index
eZ80F91 MCU
Product Specification
375
Customer Support
For answers to technical questions about the product, documentation, or any other issues
with Zilog’s offerings, visit Zilog’s Knowledge Base at http://www.zilog.com/kb.
For any comments, detail technical questions, or reporting problems, visit Zilog’s Technical Support at http://support.zilog.com.
PS019215-0910
Customer Support
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising