DS28CZ04

DS28CZ04
DS28CZ04
4Kb I²C/SMBus EEPROM
with Nonvolatile PIO
www.maxim-ic.com
GENERAL DESCRIPTION
FEATURES
The DS28CZ04 combines 4Kb (512 x 8) EEPROM
with 4 PIO lines. Communication with the device is
accomplished with an industry standard I²C and
SMBus™ interface. The memory is organized as two
segments of 256 bytes with single byte and up to 16byte block write capability. Individual PIO lines may
be configured as inputs or outputs. The power-on
state of PIO programmed as outputs is stored in nonvolatile memory. All PIO may be reconfigured by the
user through the serial interface.
ƒ
4G SFP Copper Modules
SFF-8472, SFP Fiber Modules
RAID Systems
Servers
ORDERING INFORMATION
VCC
PART
DS28CZ04G-4+
TEMP RANGE
DS28CZ04G-4+T
-40°C to +85°C
PIN-PACKAGE
TQFN12-EP* 4x4mm²
TQFN12-EP* 4x4mm²
Tape-and-Reel
-40°C to +85°C
DS28CZ04
VEET
From SFP
connector
*EP = Exposed Paddle
+Denotes lead-free package.
MAX3982
PE1
PE0
OUTLEV
IN+
INTX_DISABLE
LOS
LOSLEV
GND
PIN CONFIGURATION
OUT+
OUTConnect to
VCC or GND
SCL
PIO0
WP
A2
A1 GND
MRZ
PIO3
PIO2
PIO1
VCC2
SDA
VCC1
SDA
SCL
GND
LOS
(from receiver)
ƒ
ƒ
ƒ
ƒ
VCCT
MOD-DEF1
ƒ
ƒ
TYPICAL OPERATING CIRCUIT
MOD-DEF2
ƒ
ƒ
ƒ
APPLICATIONS
•
•
•
•
ƒ
4Kb (512 x 8) EEPROM Organized in Two 256Byte Blocks
Single Byte and up to 16-Byte EEPROM Write
Sequences
Write-Protect Control Pin for the Entire EEPROM
Array
Endurance 200k Cycles per Block at 25°C; 10ms
max EEPROM Write Cycle
4 PIO Lines
Each PIO is Configured to Input or Output Mode
on Startup by Stored Value
All PIOs are Reconfigurable after Startup
Serial Interface User-Programmable for I²C Bus
and SMBus Compatibility
Supports 100kHz and 400kHz I²C Communication Speeds
Operating Range: 2.0V to 5.25V, -40°C to +85°C
4mm x 4mm 12-Pin TQFN Package
12
11
10
EP
VEET
Small Form-factor Pluggable (SFP) Circuit
A1 1
9 WP
A2 2
8 MRZ
PIO3 3
7 VCC
4
5
6
PIO2
PIO1
PIO0
SMBus is a trademark of Intel Corp.
Thin 12-Lead 4mm × 4mm QFN (Top View)
Package Outline Drawing 21-0139
Package Code T1244+4
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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REV: 061107
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground
Maximum Current SDA, SCL, A2, A1, WP, MRZ Pin
Maximum Current each PIO Pin
Maximum GND and VCC Current
Operating Temperature Range
Junction Temperature
Storage Temperature Range
Soldering Temperature
-0.5V, +6V
±20mA
±20mA
100mA
-40°C to +85°C
+150°C
-55°C to +125°C
See IPC/JEDEC J-STD-020
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device.
ELECTRICAL CHARACTERISTICS
(-40°C to +85°C, see Note 1)
PARAMETER
SYMBOL
CONDITIONS
Supply Voltage
Standby Current (Note 2)
VCC
ICCS
Operating Current
ICCA
Programming Current
Power-up Wait Time
IPROG
tPOIP
Bus idle, VCC = 5.25V
Bus active at 400kHz,
VCC = 5.25V
VCC = 5.25V
(Note 3)
tPROG
NCYCLE
tRET
At +25°C (Notes 4, 5)
At +85°C (Notes 5, 6)
EEPROM
Programming Time
Endurance
Data Retention
PIO Pins, See Figures 8, 9
LOW-Level Output Voltage
VOL
MIN
TYP
MAX
UNITS
1.5
5.25
4
V
µA
250
500
µA
500
1000
100
µA
µs
10
ms
⎯
years
0.4
V
2.0
1mA sink current
500μA source current
200k
40
0
VCC 0.5V
HIGH-Level Output Voltage
VOH
LOW-Level Input Voltage
VIL
-0.3
0.3 × VCC
V
HIGH-Level Input Voltage
VIH
0.7 ×
VCC
VCC +
0.3V
V
Output Data Valid Time
PIO Read Setup Time
PIO Read Hold Time
tPV
tPS
tPH
Leakage Current
IL
(Note 5)
(Note 5)
High Impedance, at
VCCMAX
SCL, SDA, A2, A1, WP, MRZ Pins (Note 7), See Figure 6
LOW Level Input Voltage
VIL
HIGH Level Input Voltage
VIH
(Note 8)
Hysteresis of Schmitt Trigger
Inputs
Vhys
(Notes 5, 9)
LOW Level Output Voltage
VOL
Output Fall Time from VIhmin to
VILmax (Notes 5, 10)
Pulse Width of Spikes that are
Suppressed by the Input Filter
tof
tSP
At 4mA Sink Current,
open drain
Bus Capacitance from
10pF to 400pF
SDA and SCL pins only
(Note 5)
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V
1
µs
ns
ns
-1
+1
µA
-0.3
0.3 × VCC
VCCmax +
0.3V
V
150
150
0.7 ×
VCC
0.05 ×
VCC
20 +
0.1CB
V
V
0.4
V
250
ns
50
ns
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
PARAMETER
Input Current with an Input
Voltage Between 0.1VCC and
0.9VCCmax
Input Capacitance
SCL Clock Frequency
Bus Time-Out
Hold Time (Repeated) START
Condition. After this Period, the
First Clock Pulse is Generated.
LOW Period of the SCL Clock
(Note 13)
HIGH Period of the SCL Clock
Setup Time for a Repeated
START Condition
SYMBOL
MAX
UNITS
-10
10
µA
tTIMEOUT
(Notes 5, 9)
(Note 12)
(Note 12)
25
10
400
75
pF
kHz
ms
tHD:STA
(Note 13)
0.6
VCC ≥ 2.7V
VCC < 2.7V
(Note 13)
1.3
1.5
0.6
(Note 13)
0.6
VCC ≥ 2.7V
VCC < 2.7V
(Notes 13, 16)
(Note 13)
0.3
0.3
100
0.6
tBUF
(Note 13)
1.3
CB
(Notes 5, 13)
II
CI
fSCL
tLOW
tHIGH
tSU:STA
Data Hold Time (Notes 14, 15)
tHD:DAT
Data Setup Time
Setup Time for STOP Condition
Bus Free Time Between a
STOP and START Condition
Capacitive Load for Each Bus
Line
tSU:DAT
tSU:STO
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
Note 15:
Note 16:
CONDITIONS
(Note 11)
MIN
TYP
µs
µs
µs
µs
0.9
1.1
µs
ns
µs
µs
400
pF
Specifications at -40°C are guaranteed by design and characterization only and not production tested.
To the first order, this current is independent of the supply voltage value.
All PIO are tri-stated at beginning of reset prior to setting to Power-On values.
This specification is valid for each 16-byte memory block.
Not production tested. Guaranteed by design or characterization.
EEPROM writes can become nonfunctional after the data-retention time is exceeded. Long-time
storage at elevated temperatures is not recommended; the device can lose its write capability after 10
years at +125°C or 40 years at +85°C.
All values are referenced to VIHmin and VILmax levels.
The maximum specification value is guaranteed by design, not production tested.
Applies to SDA and SCL.
CB = total capacitance of one bus line in pF. If mixed with HS-mode devices, faster fall-times according
to I²C-Bus Specification v2.1 are allowed.
The DS28CZ04 does not obstruct the SDA and SCL lines if VCC is switched off.
The minimum SCL clock frequency is limited by the bus timeout feature. If the CM bit is 1 AND SCL
stays at the same logic level or SDA stays low for this interval, the DS28CZ04 behaves as though it
has sensed a STOP condition.
System Requirement
The DS28CZ04 provides a hold time of at least 300ns for the SDA signal (referred to the VIHmin of the
SCL signal) to bridge the undefined region of the falling edge of SCL.
The maximum tHD:DAT has only to be met if the device does not stretch the low period (tLOW) of the SCL
signal.
A Fast-mode I²C-bus device can be used in a standard-mode I²C-bus system, but the requirement
tSU:DAT ≥ 250ns must then be met. This is automatically the case if the device does not stretch the LOW
period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must
output the next data bit to the SDA line trmax + tSU:DAT = 1000 + 250 = 1250ns (according to the
standard-mode I²C-bus specification) before the SCL line is released.
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
PIN DESCRIPTION
PIN
1
2
3
4
5
6
7
8
NAME
A1
A2
PIO3
PIO2
PIO1
PIO0
VCC
MRZ
9
WP
10
11
12
EP
SCL
SDA
GND
GND
FUNCTION
Device Address Bit 1
Device Address Bit 2
PIO line #3
PIO line #2
PIO line #1
PIO line #0
Power Supply Input
Master Reset (active-low). Performs a reset of the serial interface and the PIOs without
power-cycling the device.
Write Protect input, to be connected to VCC or GND. When connected to VCC, the entire
EEPROM array is write-protected. Normal read/write access when connected to GND.
Changing the pin state during a write access will cause unpredictable results.
I²C/SMBus serial clock input; must be tied to VCC through a pullup resistor.
I²C/SMBus bidirectional serial data line; must be tied to VCC through a pullup resistor.
Ground supply for the device.
Exposed Paddle. Solder evenly to the board’s ground plane for proper operation. See
Application Note 3273 for additional information.
OVERVIEW
The DS28CZ04 consists of a serial I²C/SMBus interface, 4Kb of EEPROM and four bidirectional PIO channels, as
shown in the block diagram in Figure 1. The device communicates with a host processor through its I²C interface in
standard-mode or in fast-mode; the user can switch the interface from I²C bus to SMBus mode. Two address pins
allow 4 DS28CZ04 to reside on the same bus segment. A Master reset pin permits a full device reset without power
cycling.
The device has a memory range of 512 bytes, organized as two segments (lower half, upper half) of 256 bytes
(Figure 2). The memory map and device addressing is compatible with SFF-8472 Digital Diagnostic address
assignments. The entire EEPROM can be write-protected by tying the WP pin to VCC. The PIO pins can be
accessed through one address (= single-address mode) or through separate addresses (= multi-address mode).
PIO direct access addressing allows fast generation of data patterns and fast sampling.
The DS28CZ04 includes several EEPROM registers for the user to select whether the device powers up in SFF
mode and to define the power-on default conditions for individual PIO output state (high, low, in output mode),
individual PIO data direction (in, out), individual PIO output type (push-pull, open drain), individual PIO read bit
inversion (true, false). Once powered up, the PIO settings can be overwritten through SRAM registers without
affecting the power-on defaults.
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Figure 1. Block Diagram
SCL
SDA
A2
A1
MRZ
GND
PIO3
PIO2
PIO1
PIO0
PIO
Control
4-Kbit
EEPROM
WP
VCC
Power
Distribution
Serial
Interface
Control
Figure 2A. Memory Map (Device Address = A0h)
ADDRESS
TYPE
ACCESS
DESCRIPTION
00h to 74h
EEPROM
R/W
User memory
75h
EEPROM
R/W
Special function/user memory; controls whether
device powers-up into SFF Mode
76h
EEPROM
R/W
Power-on default for PIO output state and
direction for all PIOs
77h
EEPROM
R/W
Power-on default for PIO output type and readinversion for all PIOs
78h to 79h
⎯
R
7Ah
SRAM
R/W
Direction setting for all PIOs and device
control/status register
7Bh
SRAM
R/W
PIO read-inversion and PIO output type for all
PIOs
7Ch to 7Fh
SRAM
R/W
PIO Read/Write Access Registers
80h to FFh
EEPROM
R/W
User memory
Reserved (reads FFh)
Figure 2B. Memory Map (Device Address = A2h)
ADDRESS
TYPE
ACCESS
00h to 6Dh
EEPROM
R/W
User memory
EEPROM
R/W
SFF Mode off: User memory
⎯
R
6Fh to EFh
EEPROM
R/W
F0h to FFh
⎯
R
6Eh
DESCRIPTION
SFF Mode on: SFF Optional Status Register
User memory
Reserved (reads FFh)
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
DETAILED REGISTER DESCRIPTIONS
Special Function/User Memory (Device Address = A0h)
ADDR
b7
b6
b5
b4
b3
b2
b1
b0
75h
1
0
1
0
1
0
1
0
There is general read and write access to this address. If programmed to AAh, as shown in the bit pattern above,
the SFF Mode bit at memory address 7Ah (Device Address = A0h) will be set to 1 after the next power-up, activating SFF mode with memory address 6Eh (device address A2h) functioning as the SFF Optional Status Register.
Factory-default: 00h
Power-on Default for PIO Output State and Direction (Device Address = A0h)
ADDR
b7
b6
b5
b4
b3
b2
b1
b0
76h
POD3
POD2
POD1
POD0
POV3
POV2
POV1
POV0
There is general read and write access to this address. Factory-default: F0h
BIT DESCRIPTION
BIT(S)
DEFINITION
POV0: Power-On State
PIO0
b0
Power-on default output state of PIO0
POV1: Power-On State
PIO1
b1
Power-on default output state of PIO1
POV2: Power-On State
PIO2
b2
Power-on default output state of PIO2
POV3: Power-On State
PIO3
b3
Power-on default output state of PIO3
POD0: Power-On
Direction PIO0
b4
Power-on default direction of PIO0; 0 ⇒ output, 1 ⇒ input
POD1: Power-On
Direction PIO1
b5
Power-on default direction of PIO1; 0 ⇒ output, 1 ⇒ input
POD2: Power-On
Direction PIO2
b6
Power-on default direction of PIO2; 0 ⇒ output, 1 ⇒ input
POD3: Power-On
Direction PIO3
b7
Power-on default direction of PIO3; 0 ⇒ output, 1 ⇒ input
Power-on Default for PIO Output Type and Read Inversion (Device Address = A0h)
ADDR
b7
b6
b5
b4
b3
b2
b1
b0
77h
POT3
POT2
POT1
POT0
PIM3
PIM2
PIM1
PIM0
There is general read and write access to this address. Factory-default: F0h
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
BIT DESCRIPTION
BIT(S)
DEFINITION
PIM0: Power-On Read
Inversion PIO0
b0
Power-on default state of read-inversion bit of PIO0; 0 ⇒ no inversion,
1 ⇒ inversion
PIM1: Power-On Read
Inversion PIO1
b1
Power-on default state of read-inversion bit of PIO1; 0 ⇒ no inversion,
1 ⇒ inversion
PIM2: Power-On Read
Inversion PIO2
b2
Power-on default state of read-inversion bit of PIO2; 0 ⇒ no inversion,
1 ⇒ inversion
PIM3: Power-On Read
Inversion PIO3
b3
Power-on default state of read-inversion bit of PIO3; 0 ⇒ no inversion,
1 ⇒ inversion
POT0: Power-On Output
Type PIO0
b4
Power-on default output type of PIO0; 0 ⇒ push-pull, 1 ⇒ open drain
POT1: Power-On Output
Type PIO1
b5
Power-on default output type of PIO1; 0 ⇒ push-pull, 1 ⇒ open drain
POT2: Power-On Output
Type PIO2
b6
Power-on default output type of PIO2; 0 ⇒ push-pull, 1 ⇒ open drain
POT3: Power-On Output
Type PIO3
b7
Power-on default output type of PIO3; 0 ⇒ push-pull, 1 ⇒ open drain
Direction and Control/Status Register (Device Address = A0h)
ADDR
b7
b6
b5
b4
b3
b2
b1
b0
7Ah
ADMD
CM
BUSY
SFF
DIR3
DIR2
DIR1
DIR0
There is general read and write access to this address. Bit 5 is read-only. The power-on default of bits 0 to 3 is
copied from memory address 76h (Device Address = A0h) bits 4 to 7, respectively.
BIT DESCRIPTION
BIT(S)
DEFINITION
DIR0: Direction PIO0
b0
Direction of PIO0; 0 ⇒ output, 1 ⇒ input
DIR1: Direction PIO1
b1
Direction of PIO1; 0 ⇒ output, 1 ⇒ input
DIR2: Direction PIO2
b2
Direction of PIO2; 0 ⇒ output, 1 ⇒ input
DIR3: Direction PIO3
b3
Direction of PIO3; 0 ⇒ output, 1 ⇒ input
SFF: SFF Mode Bit
b4
SFF Mode control; 0 ⇒ SFF Mode off, 1 ⇒ SFF Mode on.
See Memory Map (Device Address = A2h) and SFF Optional Status
Register description for details. The SFF Mode Bit, when set to 1, does
not change the direction of PIO0 and PIO1 to input.
BUSY: EEPROM Busy
Indicator
b5
If this bit reads 1, an EEPROM write cycle (A0h or A2h Device Address)
is in progress. (SMBus mode only; reads 0 in I²C bus mode)
CM: Communication
Mode
b6
Selects mode for the serial communication interface.
0: I²C bus mode (power-on default)
1: SMBus mode
b7
Selects Address Mode for PIO Read/Write access. See PIO Read/Write
Access Registers for details.
0: Multi-Address Mode (power-on default)
1: Single-Address Mode
ADMD: PIO Address
Mode
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
PIO Read-Inversion and Output Type (Device Address = A0h)
ADDR
b7
b6
b5
b4
b3
b2
b1
b0
7Bh
OT3
OT2
OT1
OT0
IMSK3
IMSK2
IMSK1
IMSK0
There is general read and write access to this address. The power-on default is copied from memory address 77h
(Device Address = A0h).
BIT DESCRIPTION
BIT(S)
DEFINITION
IMSK0: Read-inversion
control of PIO0
b0
0 ⇒ no inversion, 1 ⇒ data read from PIO0 is inverted
IMSK1: Read-inversion
control of PIO1
b1
0 ⇒ no inversion, 1 ⇒ data read from PIO1 is inverted
IMSK2: Read-inversion
control of PIO2
b2
0 ⇒ no inversion, 1 ⇒ data read from PIO2 is inverted
IMSK3: Read-inversion
control of PIO3
b3
0 ⇒ no inversion, 1 ⇒ data read from PIO3 is inverted
OT0: Output Type of
PIO0
b4
0: ⇒ Push-Pull, 1 ⇒ Open Drain
OT1: Output Type of
PIO1
b5
0: ⇒ Push-Pull, 1 ⇒ Open Drain
OT2: Output Type of
PIO2
b6
0: ⇒ Push-Pull, 1 ⇒ Open Drain
OT3: Output Type of
PIO3
b7
0: ⇒ Push-Pull, 1 ⇒ Open Drain
PIO Read/Write Access Registers (Device Address = A0h)
ADDR
7Ch
7Dh
7Eh
7Fh
b7
b6
b5
b4
b3
b2
b1
b0
PIO Address Mode
IV3
IV2
IV1
IV0
OV3
OV2
OV1
OV0
Single
1
1
1
IV0
1
1
1
OV0
Multi
00h (no function)
1
1
1
IV1
1
Single
1
1
OV1
00h (no function)
1
1
1
IV2
1
Single
1
1
OV2
00h (no function)
1
1
1
IV3
1
Multi
Multi
Single
1
1
OV3
Multi
There is general read and write access to these registers. Bits shown as 1 have no function; their state cannot be
changed.
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
BIT DESCRIPTION
BIT(S)
DEFINITION
OV0: Output Value of
PIO0
⎯
Logic output state of PIO0 if DIR0 = 0 (output)
OV1: Output Value of
PIO1
⎯
Logic output state of PIO1 if DIR1 = 0 (output)
OV2: Output Value of
PIO2
⎯
Logic output state of PIO2 if DIR2 = 0 (output)
OV3: Output Value of
PIO3
⎯
Logic output state of PIO3 if DIR3 = 0 (output)
IV0: Input Value of PIO0
⎯
Logic state read from PIO0 XOR’ed with IMSK0
IV1: Input Value of PIO1
⎯
Logic state read from PIO1 XOR’ed with IMSK1
IV2: Input Value of PIO2
⎯
Logic state read from PIO2 XOR’ed with IMSK2
IV3: Input Value of PIO3
⎯
Logic state read from PIO3 XOR’ed with IMSK3
Figure 3 shows a simplified schematic of a PIO. The flip flops are accessed through the PIO R/W Access Registers
and memory addresses 7Ah and 7Bh (Device Address = A0h). They are initialized at power-up or during reset
according to the data stored at memory addresses 76h and 77h (Device Address = A0h). When a PIO is configured
as input, the PIO output is tri-stated (high impedance). When a PIO is configured as output, the PIO input is the
same as the output state XOR'ed with the corresponding read inversion bit.
Figure 3. PIO Simplified Schematic
OTn
OTn
from Serial Interface
D
Note: OTn, DIRn, OVn and IMSKn are
nonvolatile based on power-on register
values (memory addresses 76h and 77h,
device address A0h)
Q
CLK
DIRn
DIRn
from Serial Interface
D
Vcc
Q
CLK
PIOn Pin
OVn
OVn
from Serial Interface
D
Q
CLK
CLK
IVn
IMSKn
IMSKn
from Serial Interface
D
D
Q
Q
CLK
CLK
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to Serial Interface
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
SFF Optional Status Register (Device Address = A2h, only if SFF Mode is on)
ADDR
b7
b6
b5
b4
b3
b2
b1
b0
6Eh
0
0
0
0
0
TXF
LOS
0
This register is read only. The functional assignments of the individual bits are explained in the table below. Bits 0
and 3 to 7 have no function; they always read 0 and cannot be set to 1.
BIT DESCRIPTION
BIT(S)
DEFINITION
LOS: Loss Of Signal
b1
Reports the logical state of PIO0; in SFF-8472 compatible modules,
PIO0 is connected to the Loss Of Signal indicator
TXF: TX_FAULT
b2
Reports the logical state of PIO1; in SFF-8472 compatible modules,
PIO1 is connected to the TX_FAULT indicator
DEVICE OPERATION
The typical use of the DS28CZ04 in an application involves writing to and reading from the memory and accessing
the PIOs. All these activities are controlled through the I²C/SMBus serial interface. Since the DS28CZ04 has
memory areas and registers of different characteristics there are several special cases to consider. See section
Read and Write for details.
Serial Communication Interface
General Characteristics
The serial interface uses a data line (SDA) plus a clock signal (SCL) for communication. Both SDA and SCL are
bidirectional lines, connected to a positive supply voltage through a pullup resistor. When there is no
communication, both lines are HIGH. The output stages of devices connected to the bus must have an open-drain
or open-collector to perform the wired-AND function. Data can be transferred at rates of up to 100kbps in the
Standard-mode, up to 400kbps in the Fast-mode. The DS28CZ04 works in both modes.
A device that sends data on the bus is defined as a transmitter, and a device receiving data as a receiver. The
device that controls the communication is called a “master.” The devices that are controlled by the master are
“slaves.” The DS28CZ04 is a slave device.
Slave Address/Direction Byte
To be individually accessed, each device must have a slave address that does not conflict with other devices on
the bus. The slave address to which the DS28CZ04 responds is shown in Figure 4. The slave address is part of the
slave-address/direction byte. The upper 4 bits of the slave address of the DS28CZ04 are set to 1010b. Bits A1 and
A2 correspond to the A1 and A2 pins; to be selected the device must be addressed with A1 and A2 bits matching
the logical state of the respective pins.
Figure 4. DS28CZ04 Slave Address
7-Bit Slave Address
A6
A5
A4
A3
A2
A1
A0
1
0
1
0
A2
A1
P0
Most Significant Bit
Pin States
10 of 22
See Text
R/W
Determines
Read or Write
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
As a 512 byte memory device, the DS28CZ04 needs 9 address bits to access a memory location. The P0 bit
transmitted in place of the A0 address bit specifies whether the “lower half” (0b) or the “upper half” (1b) of the
memory is addressed. This causes the DS28CZ04 to occupy two logical slave addresses, one for each half of the
memory. Throughout this document, the lower half of the memory is referenced as Device Address A0h and the
upper half as Device Address A2h. The addresses A0h and A2h are correct if the A1 and A2 pins are tied to logic
0. For different conditions at these pins the slave address changes accordingly.
The last bit of the slave-address/direction byte (R/W) defines the data direction. When set to a 0, subsequent data
will flow from master to slave (write access mode); when set to a 1, data will flow from slave to master (read access
mode). Although the P0 bit is also transmitted when accessing the DS28CZ04 in read mode, its value is ignored
(don’t care); instead, the value transmitted in the most recent write access applies.
I²C/SMBus Protocol
Data transfers may be initiated only when the bus is not busy. The master generates the serial clock (SCL),
controls the bus access, generates the START and STOP conditions, and determines the number of bytes
transferred on the data line (SDA) between START and STOP. Data is transferred in bytes with the most significant
bit being transmitted first. After each byte follows an acknowledge bit to allow synchronization between master and
slave. During any data transfer, SDA must remain stable whenever the clock line is HIGH. Changes in SDA line
while SCL is high will be interpreted as a START or a STOP. The protocol is illustrated in Figure 5. For detailed
timing references see Figure 6.
Figure 5. I²C/SMBus Protocol Overview
R/W
MS-bit
ACK
bit
ACK
bit
SDA
Slave Address
Acknowledgment
from Receiver
SCL
1
Idle
START
Condition
2
6
7
8
9
ACK
Repeated if more bytes
are transferred
1
2
8
9
ACK
STOP Condition
Repeated START
Condition
Bus Idle or Not Busy
Both, SDA and SCL, are inactive, i. e., in their logic HIGH states.
START Condition
To initiate communication with a slave, the master has to generate a START condition. A START condition is
defined as a change in state of SDA from HIGH to LOW while SCL remains HIGH.
STOP Condition
To end communication with a slave, the master has to generate a STOP condition. A STOP condition is defined as
a change in state of SDA from LOW to HIGH while SCL remains HIGH.
Repeated START Condition
Repeated starts are commonly used for read accesses after having specified a memory address to read from in a
preceding write access. The master can use a repeated START condition at the end of a data transfer to
immediately initiate a new data transfer following the current one. A repeated START condition is generated the
same way as a normal START condition, but without leaving the bus idle after a STOP condition.
11 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Data Valid
With the exception of the START and STOP condition, transitions of SDA may occur only during the LOW state of
SCL. The data on SDA must remain valid and unchanged during the entire high pulse of SCL plus the required
setup and hold time (tHD:DAT after the falling edge of SCL and tSU:DAT before the rising edge of SCL, see Figure 6).
There is one clock pulse per bit of data. Data is shifted into the receiving device during the rising edge of the SCL
pulse.
When finished with writing, the master must release the SDA line for a sufficient amount of setup time (minimum
tSU:DAT + tR in Figure 6) before the next rising edge of SCL to start reading. The slave shifts out each data bit on
SDA at the falling edge of the previous SCL pulse and the data bit is valid at the rising edge of the current SCL
pulse. The master generates all SCL clock pulses, including those needed to read from a slave.
Acknowledged by Slave
Usually, a slave device, when addressed, is obliged to generate an acknowledge after the receipt of each byte. The
master must generate a clock pulse that is associated with this acknowledge bit. A device that acknowledges must
pull SDA LOW during the acknowledge clock pulse in such a way that SDA is stable LOW during the HIGH period
of the acknowledge-related clock pulse plus the required setup and hold time (tHD:DAT after the falling edge of SCL
and tSU:DAT before the rising edge of SCL).
Acknowledged by Master
To continue reading from a slave, the master is obliged to generate an acknowledge after the receipt of each byte.
The master must generate the clock pulse for each acknowledge bit and, during the acknowledge clock pulse, pull
SDA LOW in such a way that SDA is stable LOW during the HIGH period of the acknowledge-related clock pulse.
The setup and hold time (tHD:DAT after the falling edge of SCL and tSU:DAT before the rising edge of SCL) also apply
to the master.
Not Acknowledged by Slave
A slave device may be unable to receive or transmit data, e.g., because it is busy. In SMBus mode, the DS28CZ04
will always acknowledge its slave address. However, some time later the device may refuse to accept data, e.g.,
because of an invalid access mode or an EEPROM write cycle in progress. In this case the DS28CZ04 will not
acknowledge any of the bytes that it refuses and will leave SDA HIGH during the HIGH period of the acknowledgerelated clock pulse. See section Read and Write for a detailed list of situations where the DS28CZ04 does not
acknowledge.
Not Acknowledged by Master
At some time when receiving data, the master must signal an end of data to the slave device. To achieve this, the
master does not acknowledge the last byte that it has received from the slave. In response, the slave releases
SDA, allowing the master to generate the STOP condition.
Figure 6. I²C/SMBus Timing Diagram
SDA
tBUF
tHD:STA
tF
tLOW
tSP
SCL
tHD:STA
tR
tSU:STA
tHIGH
tHD:DAT
STOP START
tSU:DAT
Repeated
START
NOTE: Timing is referenced to VILMAX and VIHMIN.
12 of 22
Spike
Suppression
tSU:STO
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Read and Write
From the master’s point of view, the DS28CZ04 behaves like an memory device with an address range of 512
bytes. As indicated in the Memory Map, Figure 2, the DS28CZ04 has different types of memory: SRAM, EEPROM
and read-only areas. The write behavior depends on the memory type and the characteristics of the location that is
addressed. The SRAM registers can be written from 1 byte to multiple bytes at a time. The EEPROM can be
written from 1 byte to 16 or 8 bytes at a time, depending on the memory location.
To write to the DS28CZ04, the master must address the device in write access mode, i.e., the slave address must
be sent with the direction bit set to 0. The slave address also determines which of the memory halves is accessed.
The next byte sent in write access mode is the address of the memory location to be written to (“write pointer”) or to
start reading from (“read pointer”) if the write access is terminated without sending data (“dummy write”). Additional
bytes are taken as data for the addressed memory location.
To read from the DS28CZ04, the master must address the device in read access mode, i.e., the slave address
must be sent with the direction bit set to 1. The read pointer determines the location from which the master starts
reading. To set the pointer, the DS28CZ04 must be addressed in write access mode, as described above.
Write Access
Due to the different memory types, special function registers, PIO access registers and address modes, there are
several cases to be distinguished:
• Normal EEPROM
EEPROM block of 16 bytes
• Short EEPROM
EEPROM block of 8 bytes
• Special EEPROM
EEPROM block of 16 bytes with one or more non-writeable bytes
• Reserved
Block of 16 non-writeable bytes
• SRAM Write
SRAM bytes including PIO Read/Write Access Registers
• PIO direct
PIO Read/Write Access Registers only
Table 1A maps the various cases to the applicable memory addresses and explains the device behavior in detail.
All EEPROM writes depend on the state of WP pin. Only when the EEPROM is not write-protected (WP pin state =
0) is data accepted and transferred to the EEPROM. When writing to PIO Read/Write Registers, either by running
into their address range or by addressing them directly, one needs to further distinguish between PIO MultiAddress Mode and PIO Single Address Mode. The address mode is selected through the ADMD bit of the Direction
and Control/Status Register (Device Address A0h) at address 7Ah. In Multi-Address Mode, each PIO occupies one
memory address whereas in Single-Address Mode all PIOs share a single address. See the PIO Read/Write
Access Registers description for details. The PIO address mode does not affect the device behavior when writing
to the EEPROM sections.
Writing to EEPROM Locations
If the DS28CZ04 is addressed in write access mode, any data bytes that follow the address are written to a 16-byte
buffer, beginning at an offset that is determined by the 4 least significant bits of the target address. This buffer is
initialized (pre-loaded) with data from the addressed 16-byte EEPROM block. Incoming data replaces pre-loaded
data. With every byte received, the buffer's write pointer as well as the read pointer is incremented. If the buffer's
write pointer has reached its maximum value of 1111b (normal EEPROM and special EEPROM) or 0111b (short
EEPROM) and additional data is received, the pointer wraps around (rolls over) and the incoming data is written to
the beginning of the EEPROM write buffer and continuing. The same wrap-around applies to the 4 least-significant
bits of the read pointer. This way the read pointer maintains the last address accessed during a write operation,
incremented by one. The transfer from the buffer to the EEPROM begins when the master generates a STOP
condition. Until the write cycle is completed, the DS28CZ04 is busy for the duration of tPROG.
13 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Table 1A. Write Access
WRITING WHILE DEVICE IS NOT BUSY
PIO Mode
Starting Address
Device address = A0h,
any 16-byte block except
70h to 7Fh;
Device address = A2h,
any 16-byte block except
60h to 6Fh, F0h to FFh
(normal EEPROM)
MultiAddress
SingleAddress
SMBus or I²C Bus Mode
If WP pin is tied to GND: Slave address is acknowledged;
memory address is acknowledged, data is acknowledged;
write pointer increments and wraps around from end of block to
beginning of block, read pointer = write pointer +1.
If WP pin is tied to VCC: data is not acknowledged, no EEPROM
write cycle takes place; everything else remains the same.
Device address = A0h,
memory address from
70h to 77h (short
EEPROM)
Same as “normal EEPROM” except that write pointer wraps
around from 77h to 70h.
Device address = A2h,
memory address from
60h to 6Fh (special
EEPROM)
SFF mode off: same as “normal EEPROM”.
SFF mode on: data for address 6Eh is not acknowledged;
everything else is the same as with “normal EEPROM”.
Device address = A2h,
memory address from
F0h to FFh (reserved)
Same as “normal EEPROM” except that data is not
acknowledged.
Device address = A0h,
memory address from
78h to 7Bh (SRAM write)
Slave address is acknowledged; memory address is acknowledged, data for address 78h and 79h is not acknowledged; write
pointer increments and wraps around from 7Fh to 7Ah, read
pointer = write pointer +1.
Device address = A0h,
memory address from
7Ch to 7Fh (PIO direct)
Slave address is acknowledged; memory address is
acknowledged, data is acknowledged;
write pointer increments and wraps around from 7Fh to 7Ch,
read pointer = write pointer +1.
Device address = A0h,
memory address from
78h to 7Fh excluding
7Ch (SRAM write)
Slave address is acknowledged; memory address is
acknowledged, data for addresses 7Dh to 7Fh and 78h to 79h is
not acknowledged; write pointer increments and wraps around
from 7Fh to 7Ah, read pointer = write pointer +1.
Device address = A0h,
memory address = 7Ch
(PIO direct)
Slave address is acknowledged; memory address is
acknowledged, data is acknowledged;
write pointer stays at 7Ch; read pointer stays at 7Ch.
All other cases
Same as in PIO Multi-Address Mode.
Busy Polling
While busy, the behavior of the DS28CZ04 depends on the communication mode, which is selected through the
CM bit of the Direction and Control/Status Register (Device Address A0h) at address 7Ah. Tables 1B and 2B show
details. The PIO address mode does not affect the device behavior when busy.
In I²C bus mode, when busy the DS28CZ04 does not acknowledge its slave address until the write cycle is
completed. The master can access the device by transmitting the Slave Address/Direction Byte and testing
whether the address is acknowledged. As soon as the DS28CZ04 acknowledges, the master knows that the device
is ready for further activities.
In SMBus mode, the DS28CZ04 always acknowledges its slave address. The only way for the master to detect the
completion of the write cycle is through the BUSY bit in the Direction and Control/Status Register (Device Address
A0h) at. To get to this bit the master must first address the DS28CZ04 in write access mode, Device Address A0h,
and set the memory address to 7Ah (see Table 1B). Now the master can address the DS28CZ04 in read access
14 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
mode and generate pulses on SCL to read data, one byte after another without issuing a STOP (see Table 2B).
Eventually the BUSY bit changes from 1 to 0 indicating the end of the write cycle. The BUSY bit is sampled during
the transmission of the byte before it is read out; consequently, the state read out reflects the state at sample
time and not the actual state. To get the actual state of the busy bit the master can a) read at the maximum data
rate, b) read two bytes in sequence without delay in between and use the BUSY bit in the second byte or c) in a
loop: read one byte, issue a STOP, wait, reposition the read pointer, address the DS28CZ04 in read mode to get
another status byte.
Table 1B. Prepare For Busy Polling
WRITING WHILE DEVICE IS BUSY
PIO Mode
Starting Address
Device Address = A0h,
memory address = 7Ah
Either
Address
Mode
Device Address = A0h,
any memory address
except 7Ah
Device Address = A2h,
any memory address
SMBus Mode
Slave address is acknowledged;
memory address is acknowledged; data is not acknowledged;
write pointer keeps its last position; read pointer = 7Ah.
Slave address is acknowledged;
memory address is not acknowledged; data is not acknowledged;
write pointer keeps its last position; read pointer = write pointer
+1.
I²C Bus Mode
Slave address is NOT acknowledged; memory address is not acknowledged;
data is not acknowledged;
write pointer keeps its last
position; read pointer = write
pointer +1.
Table 2B. Busy Polling
READING WHILE DEVICE IS BUSY
PIO Mode
Read Pointer
Device Address = A0h,
memory address = 7Ah
Either
Address
Mode
Device Address = A0h,
excluding memory
address 7Ah
Device Address = A2h,
any memory address
SMBus Mode
Slave address is acknowledged;
data is delivered;
read pointer stays at 7Ah.
Slave address is acknowledged;
no data is delivered; read pointer
= last write pointer +1.
I²C Bus Mode
Slave address is NOT
acknowledged;
no data is delivered;
read pointer stays as is.
Writing to SRAM and PIO Locations
If the DS28CZ04 is addressed in write access mode, any data bytes that follow the address are directly written to
their respective memory location. The PIO address mode controls the device behavior when writing to the PIO
Read/Write access registers. Depending on whether one runs into the PIO address range (SRAM write) or whether
one starts at a PIO address (PIO direct) the pointer and data acknowledge behavior is different. Table 1A shows
the details. The PIO Address Mode is another parameter that affects the pointer behavior. Figure 7 illustrates the
possible cases and the sequence in which the addresses are accessed.
The common characteristic in both SRAM write cases is a starting address in the SRAM block (address range 78h
to 7Fh) excluding any address used for PIO access. Data for writeable registers (7Ah, 7Bh and valid addresses
for PIO Read/Write access) is acknowledged; the write pointer increments and after address 7Fh rolls over to 7Ah.
The common characteristic in both PIO direct cases is a starting address within the address range used for PIO
access. In PIO Multi-Address Mode, there are four such addresses (7Ch to 7Fh); each PIO occupies its own
address. Data is always acknowledged; the write pointer increments to the next PIO and eventually wraps around
to 7Ch. In PIO Single-Address Mode, there is exactly one address (7Ch) that is shared by all PIOs. Data is always
acknowledged; the write pointer stays at 7Ch.
15 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Figure 7. SRAM and PIO Writing
Upper
Half
Lower Half
Memory Location
Address
Function
00h to 77h
Memory
78h
Reserved
79h
Reserved
7Ah
Register
7Bh
Register
7Ch
PIO R/W
7Dh
PIO R/W
7Eh
PIO R/W
7Fh
PIO R/W
80h to FFh
Memory
00h to FFh
Memory
PIO Multi-Address Mode
SRAM Write
PIO Direct
PIO Single-Address Mode
SRAM Write
PIO Direct
When writing to a PIO, as shown in Figure 8, any state change is triggered by the SCL pulse that the master
generates for the acknowledge bit of byte written to the PIO Read/Write Access Register. After the output transition
time tPV is expired, the state change is completed. In PIO Single-Address mode all PIOs change their state
approximately at the same time; in this mode the fastest rate for a PIO to change its state is fSCL/9. In PIO MultiAddress Mode each PIO is accessed individually; in this mode when writing in an endless loop the fastest rate for a
PIO to change its state is fSCL/36. Transfer of data can be stopped at any moment by a STOP condition. When this
occurs, data present at the last acknowledged phase is valid.
Figure 8. PIO Write Access Timing
SRAM Write
SDA
MSB
(7Bh) data
LSB A MSB
DATA1
LSB A MSB
DATA2
LSB A MSB
DATA3
LSB A
SCL
tPV
PIO
DATA1
DATA2
PIO Direct
SDA
S A6 A5 A4 A3 A2 A1 P0 0
A MSB
PIO Address
LSB A MSB
DATA1
LSB A MSB
DATA2
LSB A
SCL
tPV
PIO
DATA1
Reading Memory and PIOs
If the DS28CZ04 is addressed in read access mode, the read pointer determines the location from which the
master will start reading. The read pointer is set when the DS28CZ04 is accessed in write access mode, either for
16 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
writing data or through a dummy write. At power-on the read pointer is reset to address 00h of the lower half of the
memory. A description on how the read pointer is affected during write accesses is included in Table 1A. In
contrast to write accesses where the memory is updated in small blocks of 8 or 16 bytes, all 512 bytes are readable
in a single read access. Only two cases need to be distinguished: normal read and PIO direct. Table 2A explains
the cases in detail.
Table 2A. Read Access
READING WHILE DEVICE IS NOT BUSY
PIO Mode
Read Pointer
MultiAddress
SingleAddress
SMBus or I²C Bus Mode
Anywhere excluding
device address = A0h,
memory address from
7Ch to 7Fh (normal read)
Slave address is acknowledged; data is delivered;
read pointer increments, eventually crossing from lower half to
upper half of the memory, and wraps around from upper half
FFh to lower half 00h.
Device address = A0h,
memory address from
7Ch to 7Fh (PIO direct)
Slave address is acknowledged; data is delivered;
read pointer increments and wraps around from 7Fh to 7Ch,
staying in the lower half of memory.
Anywhere excluding
device address = A0h,
memory address = 7Ch
(normal read)
Slave address is acknowledged; data is delivered;
read pointer increments, eventually crossing from lower half to
upper half of the memory, and wraps around from upper half
FFh to lower half 00h.
Device address = A0h,
memory address = 7Ch
(PIO direct)
Slave address is acknowledged; data is delivered;
read pointer stays at 7Ch.
The PIO Address Mode in conjunction with the initial read pointer position determines the sequence in which the
addresses are accessed. Figure 9 illustrates the possible cases.
Figure 9. Memory and PIO Reading
Upper
Half
Lower Half
Memory Location
Address
Function
00h to 77h
Memory
78h
Reserved
79h
Reserved
7Ah
Register
7Bh
Register
7Ch
PIO R/W
7Dh
PIO R/W
7Eh
PIO R/W
7Fh
PIO R/W
80h to FFh
Memory
00h to FFh
Memory
PIO Multi-Address Mode
Normal Read
PIO Direct
17 of 22
PIO Single-Address Mode
Normal Read
PIO Direct
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
The common characteristic in both normal read cases is a starting address anywhere in the memory excluding
any address used for PIO access. The read pointer increments after every byte read. This way a series of read
accesses reveals memory data of consecutive addresses, without any duplications or gaps. When reading from
reserved areas the master receives FFh bytes. When the end of the upper half of the memory is reached (device
address A2h, address FFh) the read pointer wraps around to the start of the lower half of the memory (device
address A0h, address 00h). When the end of the lower half of the memory is reached, the read pointer continues at
the start of the upper half of the memory. To change the read address, the master has to address the DS28CZ04 in
write access mode and specify a new memory address.
The common characteristic in both PIO direct cases is a starting address within the address range used for PIO
access. In PIO Multi-Address Mode, there are four such addresses (7Ch to 7Fh); each PIO occupies its own
address. After a byte is sent to the master, the read pointer increments to the next PIO and eventually wraps
around to 7Ch. In PIO Single-Address Mode, there is exactly one address (7Ch) that is shared by all PIOs.
Consequently, the master can continue reading, but the read pointer stays at 7Ch.
When reading from a PIO, as shown in Figure 10, the sampling takes place on the falling SCL edge of the 2nd-last
bit before the acknowledge bit. With PIO direct mode, the first sample is taken 3 SCL cycles earlier, i. e., during the
transmission of the A3 bit of the slave address. To be correctly assessed, the PIO state must not changed during
the tPS and tPH interval. In PIO Single-Address mode all PIOs are sampled simultaneously; in this mode with PIO
direct access the fastest sample rate for a PIO is fSCL/9. In PIO Multi-Address Mode each PIO is sampled individually; in this mode with PIO direct access the fastest sample rate for a PIO is fSCL/36. Transfer of data can be
stopped at any moment by a STOP condition. When this occurs, data from the last sampling instance is lost.
Figure 10. PIO Read Access Timing
Sampling
Normal Read
tPS
PIO
DATA1
Sampling
Sampling
DATA2
tPH
DATA3
DATA4
DATA5
SCL
SDA
MSB
PIO Direct
(7Bh) data
LSB A MSB
DATA2
LSB A MSB
Sampling
DATA1
DATA2
LSB A MSB
DATA4
LSB A
Sampling
Sampling
tPS
PIO
DATA3
tPH
DATA3
DATA4
DATA5
SCL
SDA
S A6 A5 A4 A3 A2 A1 P0 1
A MSB
DATA1
LSB A MSB
DATA3
LSB A MSB
DATA4
LSB A
With revision A1 devices, the sampling always takes place on the falling SCL edge of the last bit before the
acknowledge bit. The sampled data, however, is reported to the master one byte late, as shown in Figure 10A. The
first sample of PIO data that the master receives in PIO direct access should be discarded since its timing relative
to the transmission of the slave address is undefined. Any application firmware developed for revision A1 devices is
fully compatible to newer devices.
18 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Figure 10A. PIO Read Access Timing, A1 devices
Sampling
Normal Read, A1 Parts
Sampling
Sampling
tPS
PIO
DATA1
tPH
DATA2
DATA3
DATA4
DATA5
SCL
SDA
MSB
(7Bh) data
LSB A MSB
DATA1
LSB A MSB
DATA2
LSB A MSB
DATA3
LSB A
Note: DATA1 was sampled during the transmission of data from address 7Ah, or, if
reading started at memory address 7Bh, during the transmission of the slave address.
Sampling
PIO Direct, A1 Parts
Sampling
Sampling
tPS
PIO
DATA1
tPH
DATA2
DATA3
DATA4
DATA5
SCL
SDA
S A6 A5 A4 A3 A2 A1 P0 1
A MSB
DATA1
LSB A MSB
DATA2
LSB A MSB
DATA3
LSB A
Note: DATA1 was sampled during the transmission of the slave address of a preceding read or write access.
I²C/SMBus Communication—Legend
SYMBOL
S
DESCRIPTION
SYMBOL
START Condition
xx0xx1xxb
DESCRIPTION
Byte that defines specific bits only
ADL,0
Select for Write Access to lower half
P
STOP Condition
ADH,0
Select for Write Access to upper half
A\
Not Acknowledged
ADX,1
Select for Read Access
<byte>
Transfer of 1 Byte
ADX,0
Select for Write access
AMA
Any 8-bit Memory Address
Sr
Repeated START Condition
A
Acknowledged
Command-Specific Communication⎯Color-Codes
Master-to-Slave
Slave-to-Master
Programming
Communication Examples
Set I²C mode, write 3 bytes starting at address 25h, lower half of the memory, test for end of cycle
Set I²C bus mode; optional step;
S
ADL,0
A
7Ah
A
x0xxxxxxb
A
P
I²C bus mode is the power-on
default.
S
ADL,0
A
25h
A
<byte>
A
P
Programming
Write 3 bytes
S
ADX,0
A\
Sr
ADX,0
A\
Sr
ADX,0
A
P
Repeat this sequence; when cycle is completed, the DS28CZ04 will acknowledge.
19 of 22
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Set SMBus mode, write 3 bytes starting at address 25h, upper half of the memory, test for end of cycle
S
ADL,0
A
7Ah
A
S
ADH,0
A
25h
A
x1xxxxxxb
<byte>
A
A
P
Set SMBus mode; the mode
setting remains valid until
the next power-on or MRZ
Programming
reset.
P
Write 3 bytes
Set Read Pointer for polling the BUSY bit
S
ADL,0
A
7Ah
A
P
S
ADX,1
A
<byte>
A
<byte>
A
<byte>
A\
P
Repeat this sequence; when cycle is completed, the BUSY bit is 0
Read all memory, starting at the lower half of memory
S
ADL,0
A
AMA
A
Sr
ADX,1
A
<byte>
Set read pointer
select lower half
A
Read 511 bytes
<byte>
A\
P
last byte
Set SFF Mode on, read SFF Optional Status Register
S
ADL,0
A
7Ah
A
xxx1xxxxb
S
ADH,0
A
6Eh
A
P
S
ADX,1
A
<byte>
A\
P
A
P
Set SFF on
Set Read Pointer for Optional Status Register
Write to all four PIOs in Multi-Address Mode, starting at PIO0
S
ADL,0
A
7Ah
A
S
ADL,0
A
7Ch
A
0xxx0000b
<byte>
A
A
P
Set direction, PIO address mode
P
Write 4 bytes
Write to all four PIOs in Single-Address Mode
S
ADL,0
A
7Ah
A
S
ADL,0
A
7Ch
A
1xxx0000b
<byte>
A
A
P
Set direction, PIO address mode
P
Set direction, PIO address mode
P
Read from all four PIOs in Multi-Address Mode, starting at PIO1
S
ADL,0
A
7Ah
A
0xxx1111b
20 of 22
A
DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
Set Read Pointer for PIO Access Register
S
ADL,0
A
7Dh
A
P
S
ADX,1
A
<byte>
A
<byte>
A\
P
Read 3 bytes
Read from all four PIOs in Single-Address Mode
S
ADL,0
A
7Ah
A
1xxx1111b
S
ADL,0
A
7Ch
A
P
S
ADX,1
A
<byte>
A\
P
A
P
Set direction, PIO address mode
Set Read Pointer for PIO Access Register
Application Information
SDA and SCL Pullup Resistors
SDA is an open-drain output on the DS28CZ04 that requires a pullup resistor (Figure 11) to realize high logic
levels. Because the DS28CZ04 uses SCL only as input (no clock stretching) the master can drive SCL either
through an open-drain/collector output with a pullup resistor or a push-pull output.
Pullup Resistor RP Sizing
According to the I²C specification, a slave device must be able to sink at least 3mA at a VOL of 0.4V. The SMBus
specification requires a current sink capability of 4mA at 0.4V. The DS28CZ04 can sink at least 4mA at 0.4V VOL
over its entire operating voltage range. This DC characteristic determines the minimum value of the pullup resistor:
RPMIN = (VCC - 0.4V)/4mA. With a maximum operating voltage of 5.25V, the minimum value for the pullup resistor is
1.2kΩ. The "Minimum RP" line in Figure 12 shows how the minimum pullup resistor changes with the operating
(pullup) voltage.
Figure 11. Application Schematic Microprocessor Port Expander
VCC
RP
VCC
RP
To additional
devices
SDA
SCL
µC
VCC
DS28CZ04
GND
SDA
SCL
MRZ
PIO1
PIO3
PIO0
PIO2
WP
A2
A1 GND
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DS28CZ04: 4Kb I²C/SMBus EEPROM with Nonvolatile PIO
For I²C systems, the rise time and fall time are measured from 30% to 70% of the pullup voltage. The maximum
bus capacitance CB is 400pF. The maximum rise time must not exceed 300ns. Assuming maximum rise time, the
maximum resistor value at any given capacitance CB is calculated as: RPMAX = 300ns/(CB*ln(7/3)). For a bus
capacitance of 400pF the maximum pullup resistor would be 885Ω.
Since an 885Ω pullup resistor, as would be required to meet the rise time specification and 400pF bus capacitance,
is lower than RPMIN at 5.25V, a different approach is necessary. The "Max. Load…" line in Figure 12 is generated by
first calculating the minimum pullup resistor at any given operating voltage ("Minimum RP" line) and then calculating
the respective bus capacitance that yields a rise time of 300ns.
Only for pullup voltages of 4V and lower can the maximum permissible bus capacitance of 400pF be maintained. A
reduced bus capacitance of 300pF is acceptable for the entire operating voltage range. The corresponding pullup
resistor value at the voltage is indicated by the "Minimum RP" line.
Figure 12. I²C Fast Speed Pullup Resistor Selection Chart
Max. Load at Min. Rp fast mode
1200
600
1000
500
800
400
600
300
400
200
200
100
0
Load (pF)
Minimum Rp (Ohms)
"Minimum Rp"
0
2
2.5
3
3.5
4
4.5
5
Pull-up Voltage
PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to
www.maxim-ic.com/DallasPackInfo.)
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