ATtiny25/45/85 Automotive

ATtiny25/45/85 Automotive

ATtiny25/45/85 Automotive

8-bit AVR Microcontroller with 2/4/8K Bytes In-System

Programmable Flash

DATASHEET

Features

● High performance, low power AVR

®

8-bit microcontroller

Advanced RISC architecture

● 120 powerful instructions – most single clock cycle execution

● 32

×

8 general purpose working registers

● Fully static operation

Non-volatile program and data memories

● 2/4/8Kbyte of in-system programmable program memory flash (ATtiny25/45/85)

● Endurance: 10,000 write/erase cycles

● 128/256/512 bytes in-system programmable EEPROM (Atmel

®

ATtiny25/45/85)

● Endurance: 100,000 write/erase cycles

● 128/256/512 bytes internal SRAM (ATtiny25/45/85)

● Programming lock for self-programming flash program and EEPROM data security

● Peripheral features

● 8-bit Timer/Counter with prescaler and Two PWM channels

● 8-bit high speed Timer/Counter with separate prescaler

● 2 High frequency PWM outputs with separate output compare registers

● Programmable dead time generator

● Universal serial interface with start condition detector

● 10-bit ADC

● 4 Single ended channels

● 2 Differential ADC channel pairs with programmable gain (1x, 20x)

● Programmable watchdog timer with separate on-chip oscillator

● On-chip analog comparator

Special microcontroller features

● debugWIRE on-chip debug system

● In-system programmable via SPI port

● External and internal interrupt sources

● Low power idle, ADC noise reduction, and power-down modes

● Enhanced power-on reset circuit

● Programmable brown-out detection circuit

● Internal calibrated oscillator

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I/O and packages

● Six programmable I/O lines

● 8-pin SOIC

● 20-pin QFN

● Operating voltage

● 2.7 – 5.5V for Atmel

®

ATtiny25/45/85

Speed grade

● ATtiny25/45/85: 0 to 8MHz at 2.7 to 5.5V, 0 – 16MHz at 4.5 to 5.5V

Automotive temperature range

● –40°C to +125°C

● Low Power Consumption

● Active mode:

● 1MHz, 2.7V: 300µA

● Power-down mode:

● 0.2µA at 2.7V

Pin Configurations

Figure 1.

Pinout ATtiny25/45/85

SOIC

(PCINT5/RESET/ADC0/dW) PB5

(PCINT3/XTAL1/OC1B/ADC3) PB3

(PCINT4/XTAL2/CLKO/OC1B/ADC2) PB4

GND

3

4

1

2

6

5

8

7

VCC

PB2 (SCK/USCK/SCL/ADC1/T0/INT0/PCINT2)

PB1 (MISO/DO/AIN1/OC0B/OC1A/PCINT1)

PB0 (MOSI/DI/SDA/AIN0/OC0A/OC1A/AREF/PCINT0)

QFN/MLF

(PCINT5/RESET/ADC0/dW) PB5

(PCINT3/XTAL1/CLK/OC1B/ADC3) PB3

DNC

DNC

(PCINT4/XTAL2/CLKO/OC1B/ADC2) PB4

3

4

1

20 19 18 17 16

15

2 14

5

6 7 8 9 10

13

12

11

VCC

PB2 (SCK/USCK/SCL/ADC1/T0/INT0/PCINT2)

DNC

PB1 (MISO/DO/AIN1/OC0B/OC1A/PCINT1)

PB0 (MOSI/DI/SDA/AIN0/OC0A/OC1A/AREF/PCINT0)

NOTE: Bottom pad should be soldered to ground

DNC: Do Not Connect

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1.

Overview

The Atmel

®

ATtiny25/45/85 is a low-power CMOS 8-bit microcontroller based on the AVR

®

enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATtiny25/45/85 achieves throughputs approaching 1MIPS per

MHz allowing the system designer to optimize power consumption versus processing speed.

1.1

Block Diagram

Figure 1-1. Block Diagram

8-bit Databus

VCC

Stack

Pointer

Calibrated

Internal

Oscillator

Timing and

Control

GND

Program

Counter

Program

Flash

Instruction

Register

Instruction

Decoder

Control

Lines

SRAM

General

Purpose

Registers

X

Y

Z

ALU

Status

Register

Watchdog

Timer

MCU Control

Register

MCU Status

Register

Timer/

Counter 0

Timer/

Counter 1

Universal

Serial

Interface

Interrupt

Unit

Programming

Logic

Data

EEPROM

Oscillators

Data Register

Port B

Data Dir. Register

Port B

ADC/

Analog Comparator

Port B Drivers

Reset

PB0-PB5

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The AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the arithmetic logic unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers.

The Atmel

®

ATtiny25/45/85 provides the following features: 2/4/8K byte of in-system programmable flash, 128/256/512 bytes

EEPROM, 128/256/256 bytes SRAM, 6 general purpose I/O lines, 32 general purpose working registers, one 8-bit

Timer/Counter with compare modes, one 8-bit high speed Timer/Counter, universal serial interface, internal and external interrupts, a 4-channel, 10-bit ADC, a programmable watchdog timer with internal oscillator, and three software selectable power saving modes. The idle mode stops the CPU while allowing the SRAM, Timer/Counter, ADC, analog comparator, and interrupt system to continue functioning. The power-down mode saves the register contents, disabling all chip functions until the next interrupt or hardware reset. The ADC noise reduction mode stops the CPU and all I/O modules except ADC, to minimize switching noise during ADC conversions.

The device is manufactured using Atmel’s high density non-volatile memory technology. The on-chip ISP flash allows the program memory to be re-programmed in-system through an SPI serial interface, by a conventional non-volatile memory programmer or by an on-chip boot code running on the AVR core.

The ATtiny25/45/85 AVR is supported with a full suite of program and system development tools including: C compilers, macro assemblers, program debugger/simulators, in-circuit emulators, and evaluation kits.

1.2

Automotive Quality Grade

The ATtiny25/45/85 have been developed and manufactured according to the most stringent requirements of the international standard ISO-TS-16949. This data sheet contains limit values extracted from the results of extensive characterization (temperature and voltage). The quality and reliability of the ATtiny25/45/85 have been verified during regular product qualification as per AEC-Q100 grade 1.

As indicated in the ordering information paragraph, the products are available in three different temperature grades, but with

equivalent quality and reliability objectives. Different temperature identifiers have been defined as listed in Table 1-1 .

Table 1-1.

Temperature Grade Identification for Automotive Products

Temperature

–40; +85

–40; +105

–40; +125

Temperature Identifier

T

T1

Z

Comments

Similar to industrial temperature grade but with automotive quality

Reduced automotive temperature range

Full automotive temperature range

1.3

Pin Descriptions

1.3.1

VCC

Supply voltage.

1.3.2

GND

Ground.

1.3.3

Port B (PB5..PB0)

Port B is a 6-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The port B pins are tri-stated when a reset condition becomes active, even if the clock is not running.

Port B also serves the functions of various special features of the Atmel ATtiny25/45/85 as listed on

Section 9.3.2 “Alternate

Functions of Port B” on page 50

.

1.3.4

RESET

Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running. The minimum pulse length is given in

Table on page 34 . Shorter pulses are not guaranteed to generate a reset.

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2.

About Code Examples

This documentation contains simple code examples that briefly show how to use various parts of the device. These code examples assume that the part specific header file is included before compilation. Be aware that not all C compiler vendors include bit definitions in the header files and interrupt handling in C is compiler dependent. Please confirm with the C compiler documentation for more details.

3.

AVR CPU Core

3.1

Introduction

This section discusses the AVR

®

core architecture in general. The main function of the CPU core is to ensure correct program execution. The CPU must therefore be able to access memories, perform calculations, control peripherals, and handle interrupts.

3.2

Architectural Overview

Figure 3-1. Block Diagram of the AVR Architecture

Data Bus 8-bit

Flash

Program

Memory

Program

Counter

Status and

Control

Instruction

Register

32 x 8

General

Purpose

Registers

Instruction

Decoder

Control Lines

ALU

Interrupt

Unit

Watchdog

Timer

Analog

Comparator

I/O Module 1

Data

SRAM

I/O Module 2

I/O Module n

EEPROM

I/O Lines

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In order to maximize performance and parallelism, the AVR

®

uses a harvard architecture – with separate memories and buses for program and data. Instructions in the program memory are executed with a single level pipelining. While one instruction is being executed, the next instruction is pre-fetched from the program memory. This concept enables instructions to be executed in every clock cycle. The program memory is in-system reprogrammable flash memory.

The fast-access register file contains 32

×

8-bit general purpose working registers with a single clock cycle access time. This allows single-cycle arithmetic logic unit (ALU) operation. In a typical ALU operation, two operands are output from the register file, the operation is executed, and the result is stored back in the register file – in one clock cycle.

Six of the 32 registers can be used as three 16-bit indirect address register pointers for data space addressing – enabling efficient address calculations. One of the these address pointers can also be used as an address pointer for look up tables in flash program memory. These added function registers are the 16-bit X-, Y-, and Z-register, described later in this section.

The ALU supports arithmetic and logic operations between registers or between a constant and a register. Single register operations can also be executed in the ALU. After an arithmetic operation, the status register is updated to reflect information about the result of the operation.

Program flow is provided by conditional and unconditional jump and call instructions, able to directly address the whole address space. Most AVR instructions are 16-bits wide. There are also 32-bit instructions.

During interrupts and subroutine calls, the return address program counter (PC) is stored on the stack. The stack is effectively allocated in the general data SRAM, and consequently the stack size is only limited by the total SRAM size and the usage of the SRAM. All user programs must initialize the SP in the reset routine (before subroutines or interrupts are executed). The stack pointer (SP) is read/write accessible in the I/O space. The data SRAM can easily be accessed through the five different addressing modes supported in the AVR architecture.

The memory spaces in the AVR architecture are all linear and regular memory maps.

A flexible interrupt module has its control registers in the I/O space with an additional global interrupt enable bit in the status register. All interrupts have a separate interrupt vector in the interrupt vector table. The interrupts have priority in accordance with their interrupt vector position. The lower the interrupt vector address, the higher the priority.

The I/O memory space contains 64 addresses for CPU peripheral functions as control registers, SPI, and other I/O functions.

The I/O memory can be accessed directly, or as the data space locations following those of the register file, 0x20 – 0x5F.

3.3

ALU – Arithmetic Logic Unit

The high-performance AVR ALU operates in direct connection with all the 32 general purpose working registers. Within a single clock cycle, arithmetic operations between general purpose registers or between a register and an immediate are executed. The ALU operations are divided into three main categories – arithmetic, logical, and bit-functions. Some implementations of the architecture also provide a powerful multiplier supporting both signed/unsigned multiplication and fractional format. See the “instruction set” section for a detailed description.

3.4

Status Register

The status register contains information about the result of the most recently executed arithmetic instruction. This information can be used for altering program flow in order to perform conditional operations. Note that the status register is updated after all ALU operations, as specified in the instruction set reference. This will in many cases remove the need for using the dedicated compare instructions, resulting in faster and more compact code.

The status register is not automatically stored when entering an interrupt routine and restored when returning from an interrupt. This must be handled by software.

:

The AVR status register – SREG – is defined as

Bit 7 6 5

I T H

Read/Write

Initial Value

R/W

0

R/W

0

R/W

0

4

S

R/W

0

3

V

R/W

0

2

N

R/W

0

1

Z

R/W

0

0

C

R/W

0

SREG

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• Bit 7 – I: Global Interrupt Enable

The global interrupt enable bit must be set for the interrupts to be enabled. The individual interrupt enable control is then performed in separate control registers. If the global interrupt enable register is cleared, none of the interrupts are enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has occurred, and is set by the RETI instruction to enable subsequent interrupts. The I-bit can also be set and cleared by the application with the

SEI and CLI instructions, as described in the instruction set reference.

• Bit 6 – T: Bit Copy Storage

The bit copy instructions BLD (bit LoaD) and BST (bit STore) use the T-bit as source or destination for the operated bit. A bit from a register in the register file can be copied into T by the BST instruction, and a bit in T can be copied into a bit in a register in the register file by the BLD instruction.

• Bit 5 – H: Half Carry Flag

The half carry flag H indicates a half carry in some arithmetic operations. Half carry is useful in BCD arithmetic. See the

“instruction set description” for detailed information.

• Bit 4 – S: Sign Bit, S = N

V

The S-bit is always an exclusive or between the negative flag N and the two’s complement overflow flag V. See the

“instruction set description” for detailed information.

• Bit 3 – V: Two’s Complement Overflow Flag

The two’s complement overflow flag V supports two’s complement arithmetic. See the “instruction set description” for detailed information.

• Bit 2 – N: Negative Flag

The negative flag N indicates a negative result in an arithmetic or logic operation. See the “instruction set description” for detailed information.

• Bit 1 – Z: Zero Flag

The zero flag Z indicates a zero result in an arithmetic or logic operation. See the “instruction set description” for detailed information.

• Bit 0 – C: Carry Flag

The carry flag C indicates a carry in an arithmetic or logic operation. See the “instruction set description” for detailed information.

3.5

General Purpose Register File

The register file is optimized for the AVR enhanced RISC instruction set. In order to achieve the required performance and flexibility, the following input/output schemes are supported by the register file:

One 8-bit output operand and one 8-bit result input

Two 8-bit output operands and one 8-bit result input

Two 8-bit output operands and one 16-bit result input

One 16-bit output operand and one 16-bit result input

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Figure 3-2

shows the structure of the 32 general purpose working registers in the CPU.

Figure 3-2. AVR CPU General Purpose Working Registers

General

Purpose

Working

Registers

7

R13

R14

R15

R16

R2

0 Addr.

R0 0x00

R1 0x01

0x02

0x0D

0x0E

0x0F

0x10

0x11 R17

R26

R27

R28

R29

R30

R31

0x1A

0x1B

0x1C

0x1D

0x1E

0x1F

X-register low byte

X-register high byte

Y-register low byte

Y-register high byte

Z-register low byte

Z-register high byte

Most of the instructions operating on the register file have direct access to all registers, and most of them are single cycle instructions.

As shown in Figure 3-2 , each register is also assigned a data memory address, mapping them directly into the first 32

locations of the user data space. Although not being physically implemented as SRAM locations, this memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers can be set to index any register in the file.

3.5.1

The X-register, Y-register, and Z-register

The registers R26..R31 have some added functions to their general purpose usage. These registers are 16-bit address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and Z are defined as described

in Figure 3-3 .

Figure 3-3. The X-, Y-, and Z-registers

X-register

15

7

R27 (0x1B)

XH

0

XL

7

R26 (0x1A)

0

0

Y-register

15

7

R29 (0x1D)

YH

0

YL

7

0

0

R28 (0x1C)

Z-register

15

7

ZH

0

ZL

7

0

0

R31 (0x1F) R30 (0x1E)

In the different addressing modes these address registers have functions as fixed displacement, automatic increment, and automatic decrement (see the instruction set reference for details).

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3.6

Stack Pointer

The stack is mainly used for storing temporary data, for storing local variables and for storing return addresses after interrupts and subroutine calls. The stack pointer register always points to the top of the stack. Note that the stack is implemented as growing from higher memory locations to lower memory locations. This implies that a stack PUSH command decreases the stack pointer.

The stack pointer points to the data SRAM stack area where the subroutine and interrupt stacks are located. This stack space in the data SRAM must be defined by the program before any subroutine calls are executed or interrupts are enabled.

The stack pointer must be set to point above 0x60. The stack pointer is decremented by one when data is pushed onto the stack with the PUSH instruction, and it is decremented by two when the return address is pushed onto the stack with subroutine call or interrupt. The stack pointer is incremented by one when data is popped from the stack with the POP instruction, and it is incremented by two when data is popped from the stack with return from subroutine RET or return from interrupt RETI.

The AVR stack pointer is implemented as two 8-bit registers in the I/O space. The number of bits actually used is implementation dependent. Note that the data space in some implementations of the AVR architecture is so small that only

SPL is needed. In this case, the SPH register will not be present.

Bit

Read/Write

Initial Value

15

SP15

SP7

7

R/W

R/W

0

1

14

SP14

SP6

6

R/W

R/W

0

0

13

SP13

SP5

5

R/W

R/W

0

0

12

SP12

SP4

4

R/W

R/W

0

1

11

SP11

SP3

3

R/W

R/W

0

1

10

SP10

SP2

2

R/W

R/W

0

1

9

SP9

SP1

1

R/W

R/W

0

1

8

SP8

SP0

0

R/W

R/W

0

1

SPH

SPL

3.7

Instruction Execution Timing

This section describes the general access timing concepts for instruction execution. The AVR

®

CPU is driven by the CPU clock clk

CPU

, directly generated from the selected clock source for the chip. No internal clock division is used.

Figure 3-4

shows the parallel instruction fetches and instruction executions enabled by the harvard architecture and the fast access register file concept. This is the basic pipelining concept to obtain up to 1MIPS per MHz with the corresponding unique results for functions per cost, functions per clocks, and functions per power-unit.

Figure 3-4. The Parallel Instruction Fetches and Instruction Executions

T1 T2 clk

CPU

T3

1st Instruction Fetch

1st Instruction Execute

2nd Instruction Fetch

2nd Instruction Execute

3rd Instruction Fetch

3rd Instruction Execute

4th Instruction Fetch

T4

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Figure 3-5

shows the internal timing concept for the register file. In a single clock cycle an ALU operation using two register operands is executed, and the result is stored back to the destination register.

Figure 3-5. Single Cycle ALU Operation

T1 T2 T3 T4 clk

CPU

Total Execution Time

Register Operands Fetch

ALU Operation Execute

Result Write Back

3.8

Reset and Interrupt Handling

The AVR

®

provides several different interrupt sources. These interrupts and the separate reset vector each have a separate program vector in the program memory space. All interrupts are assigned individual enable bits which must be written logic one together with the global interrupt enable bit in the status register in order to enable the interrupt.

The lowest addresses in the program memory space are by default defined as the reset and interrupt vectors. The complete list of vectors is shown in

Section 8. “Interrupts” on page 42

. The list also determines the priority levels of the different interrupts. The lower the address the higher is the priority level. RESET has the highest priority, and next is INT0 – the external interrupt request 0.

When an interrupt occurs, the global interrupt enable I-bit is cleared and all interrupts are disabled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then interrupt the current interrupt routine.

The I-bit is automatically set when a return from interrupt instruction – RETI – is executed.

There are basically two types of interrupts. The first type is triggered by an event that sets the interrupt flag. For these interrupts, the program counter is vectored to the actual interrupt vector in order to execute the interrupt handling routine, and hardware clears the corresponding interrupt flag. Interrupt flags can also be cleared by writing a logic one to the flag bit position(s) to be cleared. If an interrupt condition occurs while the corresponding interrupt enable bit is cleared, the interrupt flag will be set and remembered until the interrupt is enabled, or the flag is cleared by software. Similarly, if one or more interrupt conditions occur while the global interrupt enable bit is cleared, the corresponding interrupt flag(s) will be set and remembered until the global interrupt enable bit is set, and will then be executed by order of priority.

The second type of interrupts will trigger as long as the interrupt condition is present. These interrupts do not necessarily have interrupt flags. If the interrupt condition disappears before the interrupt is enabled, the interrupt will not be triggered.

When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before any pending interrupt is served.

Note that the status register is not automatically stored when entering an interrupt routine, nor restored when returning from an interrupt routine. This must be handled by software.

When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled. No interrupt will be executed after the CLI instruction, even if it occurs simultaneously with the CLI instruction. The following example shows how this can be used to avoid interrupts during the timed EEPROM write sequence.

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Assembly Code Example

in

r16, SREG

; store SREG value

cli

; disable interrupts during timed sequence

sbi sbi out

EECR, EEMWE

; start EEPROM write

EECR, EEWE

SREG, r16

; restore SREG value (I-bit)

C Code Example

char

cSREG; cSREG = SREG;

/* store SREG value */

/*

disable interrupts during timed sequence */

_CLI();

EECR |= (1<<EEMWE);

/* start EEPROM write */

EECR |= (1<<EEWE);

SREG = cSREG;

/* restore SREG value (I-bit) */

When using the SEI instruction to enable interrupts, the instruction following SEI will be executed before any pending interrupts, as shown in this example.

Assembly Code Example

sei

; set Global Interrupt Enable

sleep

; enter sleep, waiting for interrupt

; note: will enter sleep before any pending

; interrupt(s)

C Code Example

_SEI();

/* set Global Interrupt Enable */

_SLEEP();

/* enter sleep, waiting for interrupt */

/* note: will enter sleep before any pending interrupt(s) */

3.8.1

Interrupt Response Time

The interrupt execution response for all the enabled AVR

®

interrupts is four clock cycles minimum. After four clock cycles the program vector address for the actual interrupt handling routine is executed. During this four clock cycle period, the program counter is pushed onto the stack. The vector is normally a jump to the interrupt routine, and this jump takes three clock cycles. If an interrupt occurs during execution of a multi-cycle instruction, this instruction is completed before the interrupt is served. If an interrupt occurs when the MCU is in sleep mode, the interrupt execution response time is increased by four clock cycles. This increase comes in addition to the start-up time from the selected sleep mode.

A return from an interrupt handling routine takes four clock cycles. During these four clock cycles, the program counter (two bytes) is popped back from the stack, the stack pointer is incremented by two, and the I-bit in SREG is set.

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4.

AVR ATtiny25/45/85 Memories

This section describes the different memories in the ATtiny25/45/85. The AVR architecture has two main memory spaces, the data memory and the program memory space. In addition, the ATtiny25/45/85 features an EEPROM memory for data storage. All three memory spaces are linear and regular.

4.1

In-System Re-programmable Flash Program Memory

The Atmel

®

ATtiny25/45/85 contains 2/4/8K byte on-chip in-system reprogrammable flash memory for program storage.

Since all AVR instructions are 16 or 32 bits wide, the flash is organized as 1024/2048/4096

×

16.

The flash memory has an endurance of at least 10,000 write/erase cycles. The ATtiny25/45/85 program counter (PC) is

10/11/12 bits wide, thus addressing the 1024/2048/4096 program memory locations.

Section 20. “Memory Programming” on page 123

contains a detailed description on flash data serial downloading using the SPI pins.

Constant tables can be allocated within the entire program memory address space (see the LPM – load program memory instruction description).

Timing diagrams for instruction fetch and execution are presented in

Section 3.7 “Instruction Execution Timing” on page 9

.

Figure 4-1. Program Memory Map

Program Memory

0x0000

0x03FF/0x07FF

4.2

SRAM Data Memory

Figure 4-2 on page 13

shows how the ATtiny25/45/85 SRAM memory is organized.

The lower 224/352/607 data memory locations address both the register file, the I/O memory and the internal data SRAM.

The first 32 locations address the register file, the next 64 locations the standard I/O memory, and the last 128/256/512 locations address the internal data SRAM.

The five different addressing modes for the data memory cover: Direct, indirect with displacement, indirect, indirect with pre-decrement, and indirect with post-increment. In the register file, registers R26 to R31 feature the indirect addressing pointer registers.

The direct addressing reaches the entire data space.

The indirect with displacement mode reaches 63 address locations from the base address given by the Y- or Z-register.

When using register indirect addressing modes with automatic pre-decrement and post-increment, the address registers X,

Y, and Z are decremented or incremented.

The 32 general purpose working registers, 64 I/O registers, and the 128/256/512 bytes of internal data SRAM in the

ATtiny25/45/85 are all accessible through all these addressing modes. The register file is described in

Section 3.5 “General

Purpose Register File” on page 7 .

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Figure 4-2. Data Memory Map

Data Memory

32 Registers

64 I/O Registers

0x0000 - 0x001F

0x0020 - 0x005F

0x0060

Internal SRAM

(128/256/512 x 8)

0x0DF/0x015F/0x025F

4.2.1

Data Memory Access Times

This section describes the general access timing concepts for internal memory access. The internal data SRAM access is performed in two clk

CPU

cycles as described in

Figure 4-3

.

Figure 4-3. On-chip Data SRAM Access Cycles

T1 clk

CPU

T2 T3

Address Compute Address Address valid

Data

Write

WR

Data

RD

Read

Memory Access Instruction Next Instruction

4.3

EEPROM Data Memory

The Atmel

®

ATtiny25/45/85 contains 128/256/512 bytes of data EEPROM memory. It is organized as a separate data space, in which single bytes can be read and written. The EEPROM has an endurance of at least 100,000 write/erase cycles. The access between the EEPROM and the CPU is described in the following, specifying the EEPROM address registers, the

EEPROM data register, and the EEPROM control register. For a detailed description of serial data downloading to the

EEPROM, see Section 20.6 “Serial Downloading” on page 126 .

4.3.1

EEPROM Read/Write Access

The EEPROM access registers are accessible in the I/O space.

The write access times for the EEPROM are given in Table 4-1 on page 15 . A self-timing function, however, lets the user

software detect when the next byte can be written. If the user code contains instructions that write the EEPROM, some precautions must be taken. In heavily filtered power supplies, V

CC

is likely to rise or fall slowly on power-up/down. This causes the device for some period of time to run at a voltage lower than specified as minimum for the clock frequency used.

See

Section 4.3.10 “Preventing EEPROM Corruption” on page 17 for details on how to avoid problems in these situations.

In order to prevent unintentional EEPROM writes, a specific write procedure must be followed. Refer to Section 4.3.6

“Atomic Byte Programming” on page 15 and Section 4.3.7 “Split Byte Programming” on page 15 for details on this.

When the EEPROM is read, the CPU is halted for four clock cycles before the next instruction is executed. When the

EEPROM is written, the CPU is halted for two clock cycles before the next instruction is executed.

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4.3.2

EEPROM Address Register High – EEARH

Bit

Read/Write

Initial Value

7

-

R

X

6

-

R

X

5

-

R

X

4

-

R

X

3

-

R

X

2

-

R

X

1

-

R

X

0

EEAR8

R/W

X

EEARH

• Bit 7..1 – Res6..0: Reserved Bits

These bits are reserved for future use and will always read as 0 in ATtiny25/45/85.

• Bits 0 – EEAR8: EEPROM Address

The EEPROM address register – EEARH – specifies the high EEPROM address in the 128/256/512 bytes EEPROM space.

The EEPROM data bytes are addressed linearly between 0 and 127/255/511. The initial value of EEAR is undefined. A proper value must be written before the EEPROM may be accessed.

4.3.3

EEPROM Address Register – EEARL

Bit

Read/Write

Initial Value

7 6 5 4 3 2 1 0

EEAR7 EEAR6 EEAR5 EEAR4 EEAR3 EEAR2 EEAR1 EEAR0

R R R/W R/W R/W R/W R/W R/W

X X X X X X X X

EEARL

• Bits 7..0 – EEAR7..0: EEPROM Address

The EEPROM address register – EEARL – specifies the low EEPROM address in the 128/256/512 bytes EEPROM space.

The EEPROM data bytes are addressed linearly between 0 and 127/255/511. The initial value of EEAR is undefined. A proper value must be written before the EEPROM may be accessed.

4.3.4

EEPROM Data Register – EEDR

Bit

Read/Write

Initial Value

7 6 5 4 3 2 1 0

EEDR7 EEDR6 EEDR5 EEDR4 EEDR3 EEDR2 EEDR1 EEDR0

R/W

X

R/W

X

R/W

X

R/W

X

R/W

X

R/W

X

R/W

X

R/W

X

EEDR

• Bits 7..0 – EEDR7..0: EEPROM Data

For the EEPROM write operation the EEDR register contains the data to be written to the EEPROM in the address given by the EEAR register. For the EEPROM read operation, the EEDR contains the data read out from the EEPROM at the address given by EEAR.

4.3.5

EEPROM Control Register – EECR

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5 4

EEPM1 EEPM0

R/W R/W

X X

3 2

EERIE EEMPE

R/W R/W

0 0

1

EEPE

R/W

X

0

EERE

R/W

0

EECR

• Bit 7 – Res: Reserved Bit

This bit is reserved for future use and will always read as 0 in ATtiny25/45/85. For compatibility with future AVR

®

devices, always write this bit to zero. After reading, mask out this bit.

• Bit 6 – Res: Reserved Bit

This bit is reserved in the Atmel

®

ATtiny25/45/85 and will always read as zero.

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• Bits 5, 4 – EEPM1 and EEPM0: EEPROM Programming Mode Bits

The EEPROM programming mode bits setting defines which programming action that will be triggered when writing EEPE. It is possible to program data in one atomic operation (erase the old value and program the new value) or to split the erase and

Write operations in two different operations. The programming times for the different modes are shown in

Table 4-1

. While

EEPE is set, any write to EEPMn will be ignored. During reset, the EEPMn bits will be reset to 0b00 unless the EEPROM is busy programming.

Table 4-1.

EEPROM Mode Bits

EEPM1

0

0

1

1

EEPM0

0

1

0

1

Programming Time Operation

3.4ms

1.8ms

1.8ms

Erase and write in one operation (atomic operation)

Erase only

Write only

Reserved for future use

• Bit 3 – EERIE: EEPROM Ready Interrupt Enable

Writing EERIE to one enables the EEPROM ready interrupt if the I-bit in SREG is set. Writing EERIE to zero disables the interrupt. The EEPROM ready interrupt generates a constant interrupt when non-volatile memory is ready for programming.

• Bit 2 – EEMPE: EEPROM Master Program Enable

The EEMPE bit determines whether writing EEPE to one will have effect or not.

When EEMPE is set, setting EEPE within four clock cycles will program the EEPROM at the selected address. If EEMPE is zero, setting EEPE will have no effect. When EEMPE has been written to one by software, hardware clears the bit to zero after four clock cycles.

• Bit 1 – EEPE: EEPROM Program Enable

The EEPROM Program Enable Signal EEPE is the programming enable signal to the EEPROM. When EEPE is written, the

EEPROM will be programmed according to the EEPMn bits setting. The EEMPE bit must be written to one before a logical one is written to EEPE, otherwise no EEPROM write takes place. When the write access time has elapsed, the EEPE bit is cleared by hardware. When EEPE has been set, the CPU is halted for two cycles before the next instruction is executed.

• Bit 0 – EERE: EEPROM Read Enable

The EEPROM read enable signal – EERE – is the read strobe to the EEPROM. When the correct address is set up in the

EEAR register, the EERE bit must be written to one to trigger the EEPROM read. The EEPROM read access takes one instruction, and the requested data is available immediately. When the EEPROM is read, the CPU is halted for four cycles before the next instruction is executed. The user should poll the EEPE bit before starting the read operation. If a write operation is in progress, it is neither possible to read the EEPROM, nor to change the EEAR register.

4.3.6

Atomic Byte Programming

Using atomic byte programming is the simplest mode. When writing a byte to the EEPROM, the user must write the address into the EEAR register and data into EEDR register. If the EEPMn bits are zero, writing EEPE (within four cycles after

EEMPE is written) will trigger the erase/write operation. Both the erase and write cycle are done in one operation and the

total programming time is given in Table 19-1 on page 122 . The EEPE bit remains set until the erase and write operations

are completed. While the device is busy with programming, it is not possible to do any other EEPROM operations.

4.3.7

Split Byte Programming

It is possible to split the erase and write cycle in two different operations. This may be useful if the system requires short access time for some limited period of time (typically if the power supply voltage falls). In order to take advantage of this method, it is required that the locations to be written have been erased before the write operation. But since the erase and write operations are split, it is possible to do the erase operations when the system allows doing time-critical operations

(typically after Power-up).

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4.3.8

Erase

To erase a byte, the address must be written to EEAR. If the EEPMn bits are 0b01, writing the EEPE (within four cycles after

EEMPE is written) will trigger the erase operation only (programming time is given in Table 19-1 on page 122

). The EEPE bit remains set until the erase operation completes. While the device is busy programming, it is not possible to do any other

EEPROM operations.

4.3.9

Write

To write a location, the user must write the address into EEAR and the data into EEDR. If the EEPMn bits are 0b10, writing the EEPE (within four cycles after EEMPE is written) will trigger the write operation only (programming time is given in

Table 19-1 on page 122

). The EEPE bit remains set until the write operation completes. If the location to be written has not been erased before write, the data that is stored must be considered as lost. While the device is busy with programming, it is not possible to do any other EEPROM operations.

The calibrated oscillator is used to time the EEPROM accesses. Make sure the oscillator frequency is within the requirements described in

Section 5.6.1 “Oscillator Calibration Register – OSCCAL” on page 24 .

The following code examples show one assembly and one C function for erase, write, or atomic write of the EEPROM. The examples assume that interrupts are controlled (e.g., by disabling interrupts globally) so that no interrupts will occur during execution of these functions

Assembly Code Example

EEPROM_write:

; Wait for completion of previous write

sbic

EECR,EEPE

rjmp

EEPROM_write

; Set Programming mode

ldi

r16, (0<<EEPM1)|(0<<EEPM0)

out

EECR, r16

; Set up address (r17) in address register

out

EEARL, r17

; Write data (r16) to data register

out

EEDR,r16

; Write logical one to EEMWE

sbi

EECR,EEMWE

; Start eeprom write by setting EEWE

sbi

EECR,EEWE

ret

C Code Example

void

EEPROM_write(

unsigned char

ucAddress,

unsigned char

ucData)

{

/*

Wait for completion of previous write

*/ while(EECR & (1<<EEPE))

;

/*

Set Programming mode */

EECR = (0<<EEPM1)|(0>>EEPM0)

/* Set up address and data registers */

EEARL = ucAddress;

EEDR = ucData;

/*

Write logical one to EEMWE */

EECR |= (1<<EEMWE);

/* Start eeprom write by setting EEWE */

EECR |= (1<<EEWE);

}

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The next code examples show assembly and C functions for reading the EEPROM. The examples assume that interrupts are controlled so that no interrupts will occur during execution of these functions.

Assembly Code Example

EEPROM_read:

; Wait for completion of previous write

sbic

EECR,EEPE

rjmp

EEPROM_read

; Set up address (r17) in address register

out

EEARL, r17

; Start eeprom read by writing EERE

sbi

EECR,EERE

; Read data from data register

in

r16,EEDR

ret

C Code Example

unsigned char

EEPROM_read(

unsigned char

ucAddress)

{

/* Wait for completion of previous write */

while(EECR & (1<<EEPE))

;

/* Set up address register */

EEARL = ucAddress;

/*

Start eeprom read by writing EERE */

EECR |= (1<<EERE);

/* Return data from data register */

return EEDR;

}

4.3.10 Preventing EEPROM Corruption

During periods of low V

CC

, the EEPROM data can be corrupted because the supply voltage is too low for the CPU and the

EEPROM to operate properly. These issues are the same as for board level systems using EEPROM, and the same design solutions should be applied.

An EEPROM data corruption can be caused by two situations when the voltage is too low. First, a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low.

EEPROM data corruption can easily be avoided by following this design recommendation:

Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can be done by enabling the internal brown-out detector (BOD). If the detection level of the internal BOD does not match the needed detection level, an external low V

CC

reset protection circuit can be used. If a reset occurs while a write operation is in progress, the write operation will be completed provided that the power supply voltage is sufficient.

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4.4

I/O Memory

The I/O space definition of the ATtiny25/45/85 is shown in Section “” on page 164

.

All ATtiny25/45/85 I/Os and peripherals are placed in the I/O space. All I/O locations may be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data between the 32 general purpose working registers and the I/O space. I/O registers within the address range 0x00 – 0x1F are directly bit-accessible using the SBI and CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC instructions. Refer to the instruction set section for more details. When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used.

When addressing I/O registers as data space using LD and ST instructions, 0x20 must be added to these addresses.

For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory addresses should never be written.

Some of the status flags are cleared by writing a logical one to them. Note that the CBI and SBI instructions will only operate on the specified bit, and can therefore be used on registers containing such Status Flags. The CBI and SBI instructions work with registers 0x00 to 0x1F only.

The I/O and peripherals control registers are explained in later sections.

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5.

System Clock and Clock Options

5.1

Clock Systems and their Distribution

Figure 5-1

presents the principal clock systems in the AVR

®

and their distribution. All of the clocks need not be active at a given time. In order to reduce power consumption, the clocks to modules not being used can be halted by using different sleep modes, as described in

Section 6. “Power Management and Sleep Modes” on page 28 . The clock systems are detailed

below.

Figure 5-1. Clock Distribution

ADC

General I/O

Modules

CPU Core RAM

Flash and

EEPROM clk

PCK clk

I/O clk

ADC

AVR Clock

Control Unit clk

CPU clk

FLASH

Reset Logic Watchdog Timer

Source clock Watchdog clock

System Clock

Prescaler

Clock

Multiplexer

Watchdog

Oscillator clk

PCK

PLL

Oscillator

External Clock

Crystal

Oscillator

Low-frequency

Crystal Oscillator

Calibrated RC

Oscillator

5.1.1

CPU Clock – clk

CPU

The CPU clock is routed to parts of the system concerned with operation of the AVR core. Examples of such modules are the general purpose register File, the status register and the data memory holding the stack pointer. Halting the CPU clock inhibits the core from performing general operations and calculations.

5.1.2

I/O Clock – clk

I/O

The I/O clock is used by the majority of the I/O modules, like Timer/Counter. The I/O clock is also used by the external interrupt module, but note that some external interrupts are detected by asynchronous logic, allowing such interrupts to be detected even if the I/O clock is halted.

5.1.3

Flash Clock – clk

FLASH

The flash clock controls operation of the flash interface. The flash clock is usually active simultaneously with the CPU clock.

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5.1.4

ADC Clock – clk

ADC

The ADC is provided with a dedicated clock domain. This allows halting the CPU and I/O clocks in order to reduce noise generated by digital circuitry. This gives more accurate ADC conversion results.

5.1.5

Internal PLL for Fast Peripheral Clock Generation - clk

PCK

The internal PLL in ATtiny25/45/85 generates a clock frequency that is 8x multiplied from a source input. The source of the

PLL input clock is the output of the internal RC oscillator having a frequency of 8.0MHz. Thus the output of the PLL, the fast peripheral clock is 64MHz. The fast peripheral clock, or a clock prescaled from that, can be selected as the clock source for

Timer/Counter1. See the Figure 5-2 .

The PLL is locked on the RC oscillator and adjusting the RC oscillator via OSCCAL register will adjust the fast peripheral clock at the same time. However, even if the RC oscillator is taken to a higher frequency than 8MHz, the fast peripheral clock frequency saturates at 85MHz (worst case) and remains oscillating at the maximum frequency. It should be noted that the

PLL in this case is not locked any longer with the RC oscillator clock.

Therefore, it is recommended not to take the OSCCAL adjustments to a higher frequency than 8MHz in order to keep the

PLL in the correct operating range. The internal PLL is enabled only when the PLLE bit in PLLCSR is set or the PLLCK fuse is programmed (‘0’). The bit PLOCK from PLLCSR is set when PLL is locked.

Both internal RC oscillator and PLL are switched off in power down and stand-by sleep modes.

Figure 5-2. PCK Clocking System

OSCCAL PLLE PLLCK and CKSEL FUSES CLKPS3..0

RC Oscillator

8.0MHz

PLL

8x/4x

XTAL1

XTAL2

Oscillators

Lock

Detector

Divide by 4

PLOCK

PCK

64/25.6MHz

System

Clock

Prescaler

SYSTEM

CLOCK

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5.2

Clock Sources

The device has the following clock source options, selectable by flash fuse bits as shown below. The clock from the selected source is input to the AVR

®

clock generator, and routed to the appropriate modules.

Table 5-1.

Device Clocking Options Select

(1)

Device Clocking Option

External clock

PLL clock

Calibrated internal RC oscillator 8.0MHz

Watchdog oscillator 128kHz

External low-frequency crystal

External crystal/ceramic resonator

Reserved

Note: 1.

For all fuses “1” means unprogrammed while “0” means programmed.

CKSEL3..0

0000

0001

0010

0100

0110

1000-1111

0101, 0111, 0011

The various choices for each clocking option is given in the following sections. When the CPU wakes up from power-down or power-save, the selected clock source is used to time the start-up, ensuring stable oscillator operation before instruction execution starts. When the CPU starts from reset, there is an additional delay allowing the power to reach a stable level before commencing normal operation. The watchdog oscillator is used for timing this real-time part of the start-up time. The

number of WDT oscillator cycles used for each time-out is shown in Table 5-2 .

Table 5-2.

Number of Watchdog Oscillator Cycles

Typ Time-out

4ms

64ms

Number of Cycles

512

8K (8,192)

5.3

Default Clock Source

The device is shipped with CKSEL = “0010”, SUT = “10”, and CKDIV8 programmed. The default clock source setting is therefore the internal RC oscillator running at 8MHz with longest start-up time and an initial system clock prescaling of 8.

This default setting ensures that all users can make their desired clock source setting using an in-system or high-voltage programmer.

5.4

Crystal Oscillator

XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in

Figure 5-3

. Either a quartz crystal or a ceramic resonator may be used.

C1 and C2 should always be equal for both crystals and resonators. The optimal value of the capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the electromagnetic noise of the environment. Some initial

guidelines for choosing capacitors for use with crystals are given in Table 5-3 . For ceramic resonators, the capacitor values

given by the manufacturer should be used.

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Figure 5-3. Crystal Oscillator Connections

C2

C1

XTAL2

XTAL1

GND

The oscillator can operate in three different modes, each optimized for a specific frequency range. The operating mode is selected by the fuses CKSEL3..1 as shown in

Table 5-3

.

Table 5-3.

Crystal Oscillator Operating Modes

CKSEL3..1

100

(1)

101

Frequency Range (MHz)

0.4 to 0.9

0.9 to 3.0

Recommended Range for Capacitors C1 and C2 for Use with Crystals (pF)

12 to 22

110 3.0 to 8.0

111 8.0 –

Note: 1.

This option should not be used with crystals, only with ceramic resonators.

12 to 22

12 to 22

The CKSEL0 fuse together with the SUT1..0 fuses select the start-up times as shown in Table 5-4

.

Table 5-4.

Start-up Times for the Crystal Oscillator Clock Selection

CKSEL0

0

0

0

SUT1..0

00

01

10

Start-up Time from Powerdown and Power-save

258 CK

258 CK

1KCK

(1)

(1)

(2)

Additional Delay from

Reset (V

CC

= 5.0V)

14CK + 4ms

14CK + 64ms

14CK

Recommended Usage

Ceramic resonator, fast rising power

Ceramic resonator, slowly rising power

Ceramic resonator, BOD enabled

0

1

11

00

1KCK

1KCK

(2)

(2)

14CK + 4ms

14CK + 64ms

Ceramic resonator, fast rising power

Ceramic resonator, slowly rising power

1

1

01

10

16KCK

16KCK

14CK

14CK + 4ms

Crystal oscillator, BOD enabled

Crystal oscillator, fast rising power

1 11 16KCK 14CK + 64ms

Crystal oscillator, slowly rising power

Notes: 1.

These options should only be used when not operating close to the maximum frequency of the device, and only if frequency stability at start-up is not important for the application. These options are not suitable for crystals.

2.

These options are intended for use with ceramic resonators and will ensure frequency stability at start-up.

They can also be used with crystals when not operating close to the maximum frequency of the device, and if frequency stability at start-up is not important for the application.

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5.5

Low-frequency Crystal Oscillator

To use a 32.768kHz watch crystal as the clock source for the device, the low-frequency crystal oscillator must be selected by setting CKSEL fuses to ‘0110’. The crystal should be connected as shown in

Figure 5-3 on page 22

. Refer to the 32kHz crystal oscillator application note for details on oscillator operation and how to choose appropriate values for C1 and C2.

When this oscillator is selected, start-up times are determined by the SUT fuses as shown in

Table 5-5

.

Table 5-5.

Start-up Times for the Low Frequency Crystal Oscillator Clock Selection

SUT1..0

00

01

10

Start-up Time from Power

Down and Power Save

1K CK

(1)

1K CK

(1)

32K CK

Additional Delay from Power

On Reset (V

CC

= 5.0V)

4ms

64ms

64ms

Recommended usage

Fast rising power or BOD enabled

Slowly rising power

Stable frequency at start-up

11 Reserved

Note: 1.

These options should only be used if frequency stability at start-up is not important for the application.

5.6

Calibrated Internal RC Oscillator

The calibrated internal RC oscillator provides an 8.0MHz clock. The frequency is the nominal value at 3V and 25°C. If the frequency exceeds the specification of the device (depends on V

CC

), the CKDIV8 fuse must be programmed in order to divide the internal frequency by 8 during start-up. See

Section 5.10 “System Clock Prescaler” on page 26

for more details.

This clock may be selected as the system clock by programming the CKSEL fuses as shown in Table 5-6 . If selected, it will

operate with no external components. During reset, hardware loads the calibration byte into the OSCCAL register and thereby automatically calibrates the RC oscillator. At 3V and 25°C, this calibration gives a frequency within ±1% of the nominal frequency. When this oscillator is used as the chip clock, the watchdog oscillator will still be used for the watchdog

timer and for the reset time-out. For more information on the pre-programmed calibration value, see Section 20.4

“Calibration Byte” on page 125 .

Table 5-6.

Internal Calibrated RC Oscillator Operating Modes

CKSEL3..0

0010

(1)

Note: 1.

The device is shipped with this option selected.

Nominal Frequency

8.0MHz

When this oscillator is selected, start-up times are determined by the SUT fuses as shown in

Table 5-7

.

Table 5-7.

Start-up Times for the Internal Calibrated RC Oscillator Clock Selection

SUT1..0

00

Start-up Time from Power-down

6CK

01

10

(1)

6CK

6CK

11

Note: 1.

The device is shipped with this option selected.

Additional Delay from Reset

(V

CC

= 5.0V)

14CK + 4ms

14CK + 4ms

14CK + 64ms

Reserved

Recommended Usage

BOD enabled

Fast rising power

Slowly rising power

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5.6.1

Oscillator Calibration Register – OSCCAL

Bit

Read/Write

Initial Value

7

CAL7

R/W

6

CAL6

R/W

5

CAL5

R/W

4

CAL4

R/W

3

CAL3

R/W

CAL2

R/W

Device Specific Calibration Value

2 1

CAL1

R/W

0

CAL0

R/W

OSCCAL

• Bits 7..0 – CAL7..0: Oscillator Calibration Value

Writing the calibration byte to this address will trim the internal oscillator to remove process variations from the oscillator frequency. This is done automatically during chip reset. When OSCCAL is zero, the lowest available frequency is chosen.

Writing non-zero values to this register will increase the frequency of the internal oscillator. Writing 0xFF to the register gives the highest available frequency. The calibrated oscillator is used to time EEPROM and flash access. If EEPROM or flash is written, do not calibrate to more than 8.8MHz frequency. Otherwise, the EEPROM or flash write may fail.

The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives the lowest frequency range, setting this bit to 1 gives the highest frequency range. The two frequency ranges are overlapping, in other words a setting of

OSCCAL = 0x7F gives a higher frequency than OSCCAL = 0x80.

The CAL6..0 bits are used to tune the frequency within the selected range. A setting of 0x00 gives the lowest frequency in that range, and a setting of 0x7F gives the highest frequency in the range. Incrementing CAL6..0 by 1 will give a frequency increment of less than 2% in the frequency range 7.3 to 8.1MHz.

Avoid changing the calibration value in large steps when calibrating the calibrated internal RC oscillator to ensure stable operation of the MCU. A variation in frequency of more than 2% from one cycle to the next can lead to unpredictable behavior. Changes in OSCCAL should not exceed 0x20 for each calibration. It is required to ensure that the MCU is kept in reset during such changes in the clock frequency

Table 5-8.

Internal RC Oscillator Frequency Range

OSCCAL Value

0x00

0x3F

0x7F

Min Frequency in Percentage of Nominal

Frequency

50%

75%

100%

Max Frequency in Percentage of Nominal

Frequency

100%

150%

200%

5.7

External Clock

To drive the device from an external clock source, CLKI should be driven as shown in Figure 5-4 . To run the device on an

external clock, the CKSEL fuses must be programmed to “00”.

Figure 5-4. External Clock Drive Configuration

External

Clock

Signal

CLKI

GND

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When this clock source is selected, start-up times are determined by the SUT fuses as shown in Table 5-9 .

Table 5-9.

Start-up Times for the External Clock Selection

SUT1..0

00

01

10

11

Start-up Time from Power-down and

Power-save

6CK

6CK

6CK

Additional Delay from Reset Recommended Usage

14CK

14CK + 4ms

14CK + 64ms

Reserved

BOD enabled

Fast rising power

Slowly rising power

Note that the system clock prescaler can be used to implement run-time changes of the internal clock frequency while still ensuring stable operation. Refer to

Section 5.10 “System Clock Prescaler” on page 26

for details.

5.7.1

High Frequency PLL Clock - PLL

CLK

There is an internal PLL that provides nominally 64MHz clock rate locked to the RC oscillator for the use of the peripheral

Timer/Counter1 and for the system clock source. When selected as a system clock source, by programming the CKSEL fuses to ‘0001’, it is divided by four like shown in

Table 5-10 . When this clock source is selected, start-up times are determined by the SUT fuses as shown in Table 5-11

. See also

Section 5-2 “PCK Clocking System” on page 20 .

Table 5-10. PLLCK Operating Modes

CKSEL3..0

0001

Nominal Frequency

16MHz

Table 5-11. Start-up Times for the PLLCK

SUT1..0

00

01

10

11

Start-up Time from Power Down and

Power Save

1KCK

16KCK

1KCK

16KCK

Additional Delay from Reset

(V

CC

= 5.0V)

14CK + 8ms

14CK + 8ms

14CK + 68ms

14CK + 68ms

Recommended usage

BOD enabled

Fast rising power

Slowly rising power

Slowly rising power

5.8

128 kHz Internal Oscillator

The 128kHz internal oscillator is a low power oscillator providing a clock of 128kHz. The frequency is nominal at 3V and

25°C. This clock may be select as the system clock by programming the CKSEL fuses to “11”.

When this clock source is selected, start-up times are determined by the SUT fuses as shown in Table 5-12

.

Table 5-12. Start-up Times for the 128kHz Internal Oscillator

SUT1..0

00

01

10

11

Start-up Time from Power-down and

Power-save

6CK

6CK

6CK

Additional Delay from Reset Recommended Usage

14CK

14CK + 4ms

14CK + 64ms

Reserved

BOD enabled

Fast rising power

Slowly rising power

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25

5.9

Clock Output Buffer

The device can output the system clock on the CLKO pin. To enable the output, the CKOUT fuse has to be programmed.

This mode is suitable when the chip clock is used to drive other circuits on the system. Note that the clock will not be output during reset and the normal operation of I/O pin will be overridden when the fuse is programmed. Any clock source, including the internal RC oscillator, can be selected when the clock is output on CLKO. If the system clock prescaler is used, it is the divided system clock that is output.

5.10

System Clock Prescaler

The Atmel

®

ATtiny25/45/85 system clock can be divided by setting the clock prescale register – CLKPR. This feature can be used to decrease power consumption when the requirement for processing power is low. This can be used with all clock source options, and it will affect the clock frequency of the CPU and all synchronous peripherals. clk

I/O clk

FLASH

are divided by a factor as shown in

Table 5-13 on page 27 .

, clk

ADC

, clk

CPU

, and

5.10.1 Clock Prescale Register – CLKPR

Bit

Read/Write

Initial Value

7

CLKPCE

R/W

0

R

0

6

R

0

5

R

0

4

3 2 1 0

CLKPS3 CLKPS2 CLKPS1 CLKPS0 CLKPR

R/W R/W R/W

See Bit Description

R/W

• Bit 7 – CLKPCE: Clock Prescaler Change Enable

The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. The CLKPCE bit is only updated when the other bits in CLKPR are simultaneously written to zero. CLKPCE is cleared by hardware four cycles after it is written or when the CLKPS bits are written. Rewriting the CLKPCE bit within this time-out period does neither extend the time-out period, nor clear the CLKPCE bit.

• Bits 6..4 – Res: Reserved Bits

These bits are reserved bits in the Atmel ATtiny25/45/85 and will always read as zero.

• Bits 3..0 – CLKPS3..0: Clock Prescaler Select Bits 3 - 0

These bits define the division factor between the selected clock source and the internal system clock. These bits can be written run-time to vary the clock frequency to suit the application requirements. As the divider divides the master clock input to the MCU, the speed of all synchronous peripherals is reduced when a division factor is used. The division factors are

given in Table 5-13 on page 27

.

To avoid unintentional changes of clock frequency, a special write procedure must be followed to change the CLKPS bits:

1.

Write the clock prescaler change enable (CLKPCE) bit to one and all other bits in CLKPR to zero.

2.

Within four cycles, write the desired value to CLKPS while writing a zero to CLKPCE.

Interrupts must be disabled when changing prescaler setting to make sure the write procedure is not interrupted.

The CKDIV8 fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed, the CLKPS bits will be reset to

“0000”. If CKDIV8 is programmed, CLKPS bits are reset to “0011”, giving a division factor of eight at start up. This feature should be used if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. Note that any value can be written to the CLKPS bits regardless of the CKDIV8 fuse setting. The application software must ensure that a sufficient division factor is chosen if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. The device is shipped with the

CKDIV8 fuse programmed.

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Table 5-13. Clock Prescaler Select

1

1

1

1

1

1

1

1

0

0

CLKPS3

0

0

0

0

0

0

1

1

0

0

1

1

0

0

1

1

CLKPS2

0

0

1

1

0

0

0

0

1

1

1

1

0

0

1

1

CLKPS1

0

0

0

0

1

1

0

1

0

1

0

1

0

1

0

1

CLKPS0

0

1

0

1

0

1

Clock Division Factor

1

2

16

32

4

8

64

128

256

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

5.10.2 Switching Time

When switching between prescaler settings, the system clock prescaler ensures that no glitches occur in the clock system and that no intermediate frequency is higher than neither the clock frequency corresponding to the previous setting, nor the clock frequency corresponding to the new setting.

The ripple counter that implements the prescaler runs at the frequency of the undivided clock, which may be faster than the

CPU’s clock frequency. Hence, it is not possible to determine the state of the prescaler – even if it were readable, and the exact time it takes to switch from one clock division to another cannot be exactly predicted.

From the time the CLKPS values are written, it takes between T1 + T2 and T1 + 2

×

T2 before the new clock frequency is active. In this interval, 2 active clock edges are produced. Here, T1 is the previous clock period, and T2 is the period corresponding to the new prescaler setting.

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6.

Power Management and Sleep Modes

The high performance and industry leading code efficiency makes the AVR

®

microcontrollers an ideal choice for low power applications.

Sleep modes enable the application to shut down unused modules in the MCU, thereby saving power. The AVR provides various sleep modes allowing the user to tailor the power consumption to the application’s requirements.

To enter any of the three sleep modes, the SE bit in MCUCR must be written to logic one and a SLEEP instruction must be executed. The SM1..0 bits in the MCUCR register select which sleep mode (idle, ADC noise reduction, or power-down) will be activated by the SLEEP instruction. See

Table 6-1

for a summary. If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU is then halted for four cycles in addition to the start-up time, executes the interrupt routine, and resumes execution from the instruction following SLEEP. The contents of the register file and SRAM are unaltered when the device wakes up from sleep. If a reset occurs during sleep mode, the MCU wakes up and executes from the reset vector.

Figure 5-1 on page 19

presents the different clock systems in the Atmel ATtiny25/45/85, and their distribution. The figure is helpful in selecting an appropriate sleep mode.

6.1

MCU Control Register – MCUCR

The MCU control register contains control bits for power management.

Bit

Read/Write

Initial Value

7

BODS

R/W

0

6

PUD

R/W

0

5

SE

R/W

0

4

SM1

R/W

0

3

SM0

R/W

0

2

BODSE

R/W

0

1

ISC01

R/W

0

0

ISC00

R/W

0

MCUCR

• Bit 7 – BODS: BOD Sleep

BOD disable functionality is available in some devices, only. See

Section 6.5 “Limitations” on page 29

.

In order to disable BOD during sleep (see

Table 6-2 on page 29

) the BODS bit must be written to logic one. This is controlled by a timed sequence and the enable bit, BODSE in MCUCR. First both BODS and BODSE must be set to one. Second, within four clock cycles, BODS must be set to one and BODSE must be set to zero. The BODS bit is active three clock cycles after it is set. A sleep instruction must be executed while BODS is active in order to turn off the BOD for the actual sleep mode. The BODS bit is automatically cleared after three clock cycles.

In devices where sleeping BOD has not been implemented this bit is unused and will always read zero.

• Bit 5 – SE: Sleep Enable

The SE bit must be written to logic one to make the MCU enter the sleep mode when the SLEEP instruction is executed. To avoid the MCU entering the sleep mode unless it is the programmer’s purpose, it is recommended to write the sleep enable

(SE) bit to one just before the execution of the SLEEP instruction and to clear it immediately after waking up.

• Bits 4, 3 – SM1..0: Sleep Mode Select Bits 2..0

These bits select between the three available sleep modes as shown in

Table 6-1

.

Table 6-1.

Sleep Mode Select

SM1

0

0

1

1

SM0

0

1

0

1

Sleep Mode

Idle

ADC noise reduction

Power-down

Stand-by mode

• Bit 2 – BODSE: BOD Sleep Enable

BOD disable functionality is available in some devices, only. See

Section 6.5 “Limitations” on page 29

.

The BODSE bit enables setting of BODS control bit, as explained on BODS bit description. BOD disable is controlled by a timed sequence.

This bit is unused in devices where software BOD disable has not been implemented and will read as zero in those devices.

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6.2

Idle Mode

When the SM1..0 bits are written to 00, the SLEEP instruction makes the MCU enter idle mode, stopping the CPU but allowing analog comparator, ADC, Timer/Counter, watchdog, and the interrupt system to continue operating. This sleep mode basically halts clk

CPU

and clk

FLASH

, while allowing the other clocks to run.

Idle mode enables the MCU to wake up from external triggered interrupts as well as internal ones like the timer overflow. If wake-up from the analog comparator interrupt is not required, the analog comparator can be powered down by setting the

ACD bit in the analog comparator control and status register – ACSR. This will reduce power consumption in Idle mode. If the ADC is enabled, a conversion starts automatically when this mode is entered.

6.3

ADC Noise Reduction Mode

When the SM1..0 bits are written to 01, the SLEEP instruction makes the MCU enter ADC noise reduction mode, stopping the CPU but allowing the ADC, the external interrupts, and the watchdog to continue operating (if enabled). This sleep mode halts clk

I/O

, clk

CPU

, and clk

FLASH

, while allowing the other clocks to run.

This improves the noise environment for the ADC, enabling higher resolution measurements. If the ADC is enabled, a conversion starts automatically when this mode is entered. Apart form the ADC conversion complete interrupt, only an external reset, a watchdog reset, a brown-out reset, an SPM/EEPROM ready interrupt, an external level interrupt on INT0 or a pin change interrupt can wake up the MCU from ADC noise reduction mode.

6.4

Power-down Mode

When the SM1..0 bits are written to 10, the SLEEP instruction makes the MCU enter power-down mode. In this mode, the oscillator is stopped, while the external interrupts, and the watchdog continue operating (if enabled). Only an external reset, a watchdog reset, a brown-out reset, an external level interrupt on INT0, or a pin change interrupt can wake up the MCU.

This sleep mode halts all generated clocks, allowing operation of asynchronous modules only.

Note that if a level triggered interrupt is used for wake-up from power-down mode, the changed level must be held for some time to wake up the MCU. Refer to

Section 10. “External Interrupts” on page 54 for details.

Table 6-2.

Active Clock Domains and Wake-up Sources in the Different Sleep Modes

Active Clock Domains Oscillators Wake-up Sources

Sleep Mode

Idle X

ADC Noise

Reduction

Power-down

Note: 1.

For INT0, only level interrupt.

X

X

X X

X

6.5

Limitations

BOD disable functionality has been implemented in the following devices, only:

ATtiny25, revision D, and newer

ATtiny45, revision D, and newer

ATtiny85, revision C, and newer

X

X

(1)

X

(1)

X

X

X

X

X

X

X

X X

X

X

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6.6

Power Reduction Register

The power reduction register, PRR, provides a method to stop the clock to individual peripherals to reduce power consumption. The current state of the peripheral is frozen and the I/O registers can not be read or written. Resources used by the peripheral when stopping the clock will remain occupied, hence the peripheral should in most cases be disabled before stopping the clock. Waking up a module, which is done by clearing the bit in PRR, puts the module in the same state as before shutdown.

Module shutdown can be used in idle mode and active mode to significantly reduce the overall power consumption. In all other sleep modes, the clock is already stopped.

Bit

Read/Write

Initial Value

R

0

7

R

0

6

-

R

0

5

-

R

0

4

-

3 2

PRTIM1 PRTIM0

R/W

0

R/W

0

1 0

PRUSI PRADC

R/W

0

R/W

0

PRR

• Bits 7, 6, 5, 4- Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bit 3- PRTIM1: Power Reduction Timer/Counter1

Writing a logic one to this bit shuts down the Timer/Counter1 module. When the Timer/Counter1 is enabled, operation will continue like before the shutdown.

• Bit 2- PRTIM0: Power Reduction Timer/Counter0

Writing a logic one to this bit shuts down the Timer/Counter0 module. When the Timer/Counter0 is enabled, operation will continue like before the shutdown.

• Bit 1 - PRUSI: Power Reduction USI

Writing a logic one to this bit shuts down the USI by stopping the clock to the module. When waking up the USI again, the

USI should be re initialized to ensure proper operation.

• Bit 0 - PRADC: Power Reduction ADC

Writing a logic one to this bit shuts down the ADC. The ADC must be disabled before shut down. The analog comparator cannot use the ADC input MUX when the ADC is shut down.

6.7

Minimizing Power Consumption

There are several issues to consider when trying to minimize the power consumption in an AVR

®

controlled system. In general, sleep modes should be used as much as possible, and the sleep mode should be selected so that as few as possible of the device’s functions are operating. All functions not needed should be disabled. In particular, the following modules may need special consideration when trying to achieve the lowest possible power consumption.

6.7.1

Analog to Digital Converter

If enabled, the ADC will be enabled in all sleep modes. To save power, the ADC should be disabled before entering any sleep mode. When the ADC is turned off and on again, the next conversion will be an extended conversion. Refer to

Section 17. “Analog to Digital Converter” on page 101 for details on ADC operation.

6.7.2

Analog Comparator

When entering Idle mode, the analog comparator should be disabled if not used. When entering ADC noise reduction mode, the analog comparator should be disabled. In the other sleep modes, the analog comparator is automatically disabled.

However, if the analog comparator is set up to use the Internal voltage reference as input, the analog comparator should be disabled in all sleep modes. Otherwise, the internal voltage reference will be enabled, independent of sleep mode. Refer to

Section 16. “Analog Comparator” on page 98 for details on how to configure the analog comparator.

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6.7.3

Brown-out Detector

If the brown-out detector is not needed in the application, this module should be turned off. If the brown-out detector is enabled by the BODLEVEL fuses, it will be enabled in all sleep modes, and hence, always consume power. In the deeper

sleep modes, this will contribute significantly to the total current consumption. Refer to Section 7.5 “Brown-out Detection” on page 35

for details on how to configure the brown-out detector.

6.7.4

Internal Voltage Reference

The internal voltage reference will be enabled when needed by the brown-out detection, the analog comparator or the ADC.

If these modules are disabled as described in the sections above, the internal voltage reference will be disabled and it will not be consuming power. When turned on again, the user must allow the reference to start up before the output is used. If the reference is kept on in sleep mode, the output can be used immediately. Refer to

Section 7.8 “Internal Voltage

Reference” on page 37 for details on the start-up time.

6.7.5

Watchdog Timer

If the watchdog timer is not needed in the application, this module should be turned off. If the watchdog timer is enabled, it will be enabled in all sleep modes, and hence, always consume power. In the deeper sleep modes, this will contribute

significantly to the total current consumption. Refer to Section 7.9 “Watchdog Timer” on page 38 for details on how to

configure the watchdog timer.

6.7.6

Port Pins

When entering a sleep mode, all port pins should be configured to use minimum power. The most important thing is then to ensure that no pins drive resistive loads. In sleep modes where both the I/O clock (clk

I/O

) and the ADC clock (clk

ADC

) are stopped, the input buffers of the device will be disabled. This ensures that no power is consumed by the input logic when not needed. In some cases, the input logic is needed for detecting wake-up conditions, and it will then be enabled. Refer to the

Section 9.2.5 “Digital Input Enable and Sleep Modes” on page 47 for details on which pins are enabled. If the input buffer is

enabled and the input signal is left floating or has an analog signal level close to V

CC power.

/2, the input buffer will use excessive

For analog input pins, the digital input buffer should be disabled at all times. An analog signal level close to V

CC

/2 on an input pin can cause significant current even in active mode. Digital input buffers can be disabled by writing to the digital input disable register (DIDR0). Refer to

Section 16.3.1 “Digital Input Disable Register 0 – DIDR0” on page 100

for details.

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7.

System Control and Reset

7.1

Resetting the AVR

During reset, all I/O registers are set to their initial values, and the program starts execution from the reset vector. The instruction placed at the reset vector must be a RJMP – relative jump – instruction to the reset handling routine. If the program never enables an interrupt source, the interrupt vectors are not used, and regular program code can be placed at these locations. The circuit diagram in

Figure 7-1 on page 33

shows the reset logic.

Table on page 34

defines the electrical parameters of the reset circuitry.

The I/O ports of the AVR

®

are immediately reset to their initial state when a reset source goes active. This does not require any clock source to be running.

After all reset sources have gone inactive, a delay counter is invoked, stretching the internal reset. This allows the power to reach a stable level before normal operation starts. The time-out period of the delay counter is defined by the user through

the SUT and CKSEL fuses. The different selections for the delay period are presented in Section 5.2 “Clock Sources” on page 21

.

7.2

Reset Sources

The Atmel

®

ATtiny25/45/85 has four sources of reset:

Power-on reset. The MCU is reset when the supply voltage is below the power-on reset threshold (V

POT

).

External reset. The MCU is reset when a low level is present on the RESET pin for longer than the minimum pulse length.

Watchdog reset. The MCU is reset when the watchdog timer period expires and the watchdog is enabled.

Brown-out reset. The MCU is reset when the supply voltage V

CC

is below the brown-out reset threshold (V

BOT

) and the brown-out detector is enabled.

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Figure 7-1. Reset Logic

VCC

Power-on Reset

Circuit

BODLEVEL [1..0]

RESET

Pull-up Resistor

Spike

Filter

Brown-out

Reset Circuit

Reset Circuit

Watchdog

Timer

Watchdog

Oscillator

Clock

Generator

CK

CKSEL[1:0]

SUT[1:0]

DATA BUS

MCU Status

Register (MCUSR)

Delay Counters

TIMEOUT

S

R

Q

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7.3

Power-on Reset

A power-on reset (POR) pulse is generated by an on-chip detection circuit. The detection level is defined in

Table

. The POR is activated whenever V

CC

is below the detection level. The POR circuit can be used to trigger the start-up reset, as well as to detect a failure in supply voltage.

A power-on reset (POR) circuit ensures that the device is reset from power-on. Reaching the power-on reset threshold voltage invokes the delay counter, which determines how long the device is kept in RESET after V

CC is activated again, without any delay, when V

CC

decreases below the detection level.

rise. The RESET signal

Figure 7-2. MCU Start-up, RESET Tied to V

CC

V

CCRR

V

CC

V

PORMAX

V

PORMIN

RESET

Time-out

V

RST t

TOUT

Internal

Reset

Figure 7-3. MCU Start-up, RESET Extended Externally

V

CC

V

POT

RESET

V

RST t

TOUT

Time-out

Internal

Reset

Table 7-1.

Power On Reset Specifications

Parameter

Power-on reset threshold voltage (rising)

Power-on reset threshold voltage (falling)

(1)

Symbol

V

POT

Min

1.1

0.8

VCC Max. start voltage to ensure internal power-on reset signal

VCC Min. start voltage to ensure internal power-on reset signal

V

V

PORMAX

PORMIN

–0.1

VCC rise rate to ensure power-on reset V

CCRR

0.01

RESET pin threshold voltage V

RST

Note: 1.

Before rising the supply has to be between V

PORMIN and V

0.1 V

CC

PORMAX to ensure reset.

Typ

1.4

1.3

Max

1.7

1.6

0.4

0.9V

CC

Units

V

V

V

V

V/ms

V

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7.4

External Reset

An external reset is generated by a low level on the RESET pin if enabled. Reset pulses longer than the minimum pulse

width (see Table on page 34

) will generate a reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset. When the applied signal reaches the reset threshold voltage – V

RST counter starts the MCU after the time-out period – t

TOUT

– has expired.

– on its positive edge, the delay

Figure 7-4. External Reset During Operation

V

CC

V

RST

RESET

Time-out t

TOUT

Internal

Reset

7.5

Brown-out Detection

ATtiny25/45/85 has an on-chip brown-out detection (BOD) circuit for monitoring the V

CC

level during operation by comparing it to a fixed trigger level. The trigger level for the BOD can be selected by the BODLEVEL fuses. The trigger level has a hysteresis to ensure spike free brown-out detection. The hysteresis on the detection level should be interpreted as

V

BOT+

= V

BOT

+ V

HYST

/2 and V

BOT

– = V

BOT

– V

HYST

/2.

Table 7-2.

BODLEVEL Fuse Coding

(1)

BODLEVEL [2..0] Fuses

111

110

101

Min V

1.7

2.5

BOT

Typ V

1.8

2.7

BOT

BOD Disabled

Max V

2.0

2.9

BOT

Units

100

011

010

4.0

4.3

2.3

(2)

2.2

(2)

1.9

(2)

4.6

V

001

000 2.0

(2)

Notes: 1.

V

BOT

may be below nominal minimum operating voltage for some devices. For devices where this is the case, the device is tested down to V occur before V

CC

CC

= V

BOT

during the production test. This guarantees that a brown-out reset will

drops to a voltage where correct operation of the microcontroller is no longer guaranteed.

2.

Centered value, not tested.

Table 7-3.

Brown-out Characteristics

Parameter

RAM retention voltage

(1)

Brown-out detector hysteresis

Symbol

V

RAM

V

HYST

Min

Min pulse width on brown-out reset t

BOD

Note: 1.

This is the limit to which VDD can be lowered without losing RAM data

Typ

50

50

2

Max Units

mV mV

µs

When the BOD is enabled, and V

CC

decreases to a value below the trigger level (V immediately activated. When V after the time-out period t

TOUT

CC

increases above the trigger level (V

BOT+

has expired.

BOT

– in

Figure 7-5

), the brown-out reset is

in

Figure 7-5 ), the delay counter starts the MCU

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35

The BOD circuit will only detect a drop in V

CC

Table 7-1 on page 34

.

if the voltage stays below the trigger level for longer than t

BOD

given in

Figure 7-5. Brown-out Reset During Operation

V

CC

V

BOT-

RESET

V

BOT+ t

TOUT

Time-out

Internal

Reset

7.6

Watchdog Reset

When the watchdog times out, it will generate a short reset pulse of one CK cycle duration. On the falling edge of this pulse, the delay timer starts counting the time-out period t

TOUT operation of the watchdog timer.

. Refer to Section 7.9 “Watchdog Timer” on page 38

for details on

Figure 7-6. Watchdog Reset During Operation

V

CC

RESET

1 CK Cycle

WDT

Time-out

RESET

Time-out

Internal

Reset t

TOUT

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7.7

MCU Status Register – MCUSR

The MCU status register provides information on which reset source caused an MCU reset.

Bit

Read/Write

Initial Value

R

0

7

R

0

6

R

0

5

R

0

4

3

WDRF

R/W

2

BORF

1

EXTRF

R/W R/W

See Bit Description

0

PORF

R/W

MCUSR

• Bits 7..4 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bit 3 – WDRF: Watchdog Reset Flag

This bit is set if a watchdog reset occurs. The bit is reset by a power-on reset, or by writing a logic zero to the flag.

• Bit 2 – BORF: Brown-out Reset Flag

This bit is set if a brown-out reset occurs. The bit is reset by a power-on reset, or by writing a logic zero to the flag.

• Bit 1 – EXTRF: External Reset Flag

This bit is set if an external reset occurs. The bit is reset by a power-on reset, or by writing a logic zero to the flag.

• Bit 0 – PORF: Power-on Reset Flag

This bit is set if a power-on reset occurs. The bit is reset only by writing a logic zero to the flag.

To make use of the reset flags to identify a reset condition, the user should read and then reset the MCUSR as early as possible in the program. If the register is cleared before another reset occurs, the source of the reset can be found by examining the reset flags.

7.8

Internal Voltage Reference

Atmel ATtiny25/45/85 features an internal bandgap reference. This reference is used for brown-out detection, and it can be used as an input to the analog comparator or the ADC.

7.8.1

Voltage Reference Enable Signals and Start-up Time

The voltage reference has a start-up time that may influence the way it should be used. The start-up time is given in

Table 7-4

. To save power, the reference is not always turned on. The reference is on during the following situations:

1.

When the BOD is enabled (by programming the BODLEVEL [2..0] fuse bits).

2.

When the bandgap reference is connected to the analog comparator (by setting the ACBG bit in ACSR).

3.

When the ADC is enabled.

Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC, the user must always allow the reference to start up before the output from the analog comparator or ADC is used. To reduce power consumption in power-down mode, the user can avoid the three conditions above to ensure that the reference is turned off before entering power-down mode.

Table 7-4.

Internal Voltage Reference Characteristics

Parameter

Bandgap reference voltage

Bandgap reference start-up time

Bandgap reference current consumption

Condition

V

CC

= 1.1V/2.7V,

T

A

= 25°C

V

CC

= 2.7V, T

A

= 25°C

V

CC

= 2.7V, T

A

= 25°C

Symbol

V

BG t

BG

I

BG

Min

1.0

Typ

1.1

40

15

Max

1.2

70

Units

V

µs

µA

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7.9

Watchdog Timer

The watchdog timer is clocked from an on-chip oscillator which runs at 128kHz. By controlling the watchdog timer prescaler, the watchdog reset interval can be adjusted as shown in

Table 7-7 on page 40

. The WDR – watchdog reset – instruction resets the watchdog timer. The watchdog timer is also reset when it is disabled and when a chip reset occurs. Ten different clock cycle periods can be selected to determine the reset period. If the reset period expires without another watchdog reset, the Atmel

®

ATtiny25/45/85 resets and executes from the reset vector. For timing details on the watchdog reset, refer to

Table 7-7 on page 40

.

The watchdog timer can also be configured to generate an interrupt instead of a reset. This can be very helpful when using the watchdog to wake-up from power-down.

To prevent unintentional disabling of the watchdog or unintentional change of time-out period, two different safety levels are

selected by the fuse WDTON as shown in Table 7-5

Refer to Section 7.10 “Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 41 for details.

Table 7-5.

WDT Configuration as a Function of the Fuse Settings of WDTON

WDTON

Unprogrammed

Programmed

Safety Level

1

2

WDT Initial State

Disabled

Enabled

How to Disable the WDT

Timed sequence

Always enabled

How to Change Time-out

No limitations

Timed sequence

Figure 7-7. Watchdog Timer

128kHz

Oscillator

Watchdog

Prescaler

Watchdog

Reset

WDP0

WDP1

WDP2

WDP3

WDE

MCU Reset

7.9.1

Watchdog Timer Control Register – WDTCR

Bit

Read/Write

Initial Value

7

WDIF

R/W

0

6

WDIE

R/W

0

5

WDP3

R/W

0

4

WDCE

R/W

0

3

WDE

R/W

X

2

WDP2

R/W

0

1

WDP1

R/W

0

0

WDP0

R/W

0

WDTCR

• Bit 7 – WDIF: Watchdog Timeout Interrupt Flag

This bit is set when a time-out occurs in the watchdog timer and the watchdog timer is configured for interrupt. WDIF is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, WDIF is cleared by writing a logic one to the flag. When the I-bit in SREG and WDIE are set, the watchdog time-out interrupt is executed.

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• Bit 6 – WDIE: Watchdog Timeout Interrupt Enable

When this bit is written to one, WDE is cleared, and the I-bit in the status register is set, the watchdog time-out interrupt is enabled. In this mode the corresponding interrupt is executed instead of a reset if a time-out in the watchdog timer occurs.

If WDE is set, WDIE is automatically cleared by hardware when a time-out occurs. This is useful for keeping the watchdog reset security while using the interrupt. After the WDIE bit is cleared, the next time-out will generate a reset. To avoid the watchdog reset, WDIE must be set after each interrupt.

Table 7-6.

Watchdog Timer Configuration

WDE

0

0

1

1

WDIE

0

1

0

1

Watchdog Timer State

Stopped

Running

Running

Running

Action on Time-out

None

Interrupt

Reset

Interrupt

• Bit 4 – WDCE: Watchdog Change Enable

This bit must be set when the WDE bit is written to logic zero. Otherwise, the watchdog will not be disabled. Once written to one, hardware will clear this bit after four clock cycles. Refer to the description of the WDE bit for a watchdog disable procedure. This bit must also be set when changing the prescaler bits. See

Section 7.10 “Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 41

• Bit 3 – WDE: Watchdog Enable

When the WDE is written to logic one, the watchdog timer is enabled, and if the WDE is written to logic zero, the watchdog timer function is disabled. WDE can only be cleared if the WDCE bit has logic level one. To disable an enabled watchdog timer, the following procedure must be followed:

1.

In the same operation, write a logic one to WDCE and WDE. A logic one must be written to WDE even though it is set to one before the disable operation starts.

2.

Within the next four clock cycles, write a logic 0 to WDE. This disables the watchdog.

In safety level 2, it is not possible to disable the watchdog timer, even with the algorithm described above. See Section 7.10

“Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 41

In safety level 1, WDE is overridden by WDRF in MCUSR. See Section 7.7 “MCU Status Register – MCUSR” on page 37

for description of WDRF. This means that WDE is always set when WDRF is set. To clear WDE, WDRF must be cleared before disabling the Watchdog with the procedure described above. This feature ensures multiple resets during conditions causing failure, and a safe start-up after the failure.

Note: If the watchdog timer is not going to be used in the application, it is important to go through a watchdog disable procedure in the initialization of the device. If the watchdog is accidentally enabled, for example by a runaway pointer or brown-out condition, the device will be reset, which in turn will lead to a new watchdog reset. To avoid this situation, the application software should always clear the WDRF flag and the WDE control bit in the initialization routine.

• Bits 5, 2..0 – WDP3..0: Watchdog Timer Prescaler 3, 2, 1, and 0

The WDP3..0 bits determine the watchdog timer prescaling when the watchdog timer is enabled. The different prescaling values and their corresponding time-out periods are shown in

Table 7-7

.

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Table 7-7.

Watchdog Timer Prescale Select

0

0

0

0

WDP3

0

0

0

1

1

0

1

WDP2

0

0

0

0

1

1

0

WDP1

0

0

1

1

0

1

0

WDP0

0

1

0

Number of WDT Oscillator Cycles

2Kcycles

4Kcycles

8Kcycles

16Kcycles

32Kcycles

64Kcycles

128Kcycles

1

1

0

1

0

0

1

0

0

1

1

0

1

0

1

0

256Kcycles

512Kcycles

1024Kcycles

1

1

1

1

0

1

1

1

1

0

0

1

1

0

1

0

1 1 1 1

Note: 1.

If selected, one of the valid settings below 0b1010 will be used.

Reserved

(1)

Typical Time-out at

V

CC

= 5.0V

16ms

32ms

64ms

0.125s

0.25s

0.5s

1.0s

2.0s

4.0s

8.0s

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.

The following code example shows one assembly and one C function for turning off the WDT. The example assumes that interrupts are controlled (e.g., by disabling interrupts globally) so that no interrupts will occur during execution of these functions

Assembly Code Example

(1)

WDT_off:

WDR

; Clear WDRF in MCUSR

ldi

r16, (0<<WDRF)

out

MCUSR, r16

; Write logical one to WDCE and WDE

; Keep old prescaler setting to prevent unintentional Watchdog

Reset

in ori

r16, WDTCR

r16, (1<<WDCE)|(1<<WDE)

WDTCR, r16

out

; Turn off WDT

ldi

r16, (0<<WDE)

out

WDTCR, r16

ret

C Code Example

(1)

void

WDT_off(

void

)

{

_WDR();

/*

Clear WDRF in MCUSR

*/

MCUSR = 0x00

/*

Write logical one to WDCE and WDE

*/

WDTCR |= (1<<WDCE) | (1<<WDE);

/* Turn off WDT */

WDTCR = 0x00;

}

Note: 1.

The example code assumes that the part specific header file is included.

7.10

Timed Sequences for Changing the Configuration of the Watchdog Timer

The sequence for changing configuration differs slightly between the two safety levels. Separate procedures are described for each level.

7.10.1 Safety Level 1

In this mode, the watchdog timer is initially disabled, but can be enabled by writing the WDE bit to one without any restriction.

A timed sequence is needed when disabling an enabled watchdog timer. To disable an enabled watchdog timer, the following procedure must be followed:

1.

In the same operation, write a logic one to WDCE and WDE. A logic one must be written to WDE regardless of the previous value of the WDE bit.

2.

Within the next four clock cycles, in the same operation, write the WDE and WDP bits as desired, but with the

WDCE bit cleared.

7.10.2 Safety Level 2

In this mode, the watchdog timer is always enabled, and the WDE bit will always read as one. A timed sequence is needed when changing the watchdog time-out period. To change the watchdog time-out, the following procedure must be followed:

1.

In the same operation, write a logical one to WDCE and WDE. Even though the WDE always is set, the WDE must be written to one to start the timed sequence.

2.

Within the next four clock cycles, in the same operation, write the WDP bits as desired, but with the WDCE bit cleared. The value written to the WDE bit is irrelevant.

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8.

Interrupts

This section describes the specifics of the interrupt handling as performed in Atmel

®

ATtiny25/45/85. For a general explanation of the AVR

®

interrupt handling, refer to

Section 3.8 “Reset and Interrupt Handling” on page 10

.

8.1

Interrupt Vectors in ATtiny25/45/85

Table 8-1.

Reset and Interrupt Vectors

12

13

14

15

10

11

8

9

Vector No.

1

2

3

6

7

4

5

Program Address Source

0x0000 RESET

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

0x0009

0x000A

0x000B

0x000C

0x000D

0x000E

INT0

PCINT0

TIM1_COMPA Timer/Counter1 compare match A

TIM1_OVF

TIM0_OVF

EE_RDY

ANA_COMP

ADC

WDT

USI_START

USI_OVF

Interrupt Definition

External pin, power-on reset, brown-out reset, watchdog reset

External interrupt request 0

Pin change interrupt request 0

Timer/Counter1 overflow

Timer/Counter0 overflow

EEPROM ready

Analog comparator

ADC conversion complete

TIM1_COMPB Timer/Counter1 compare match B

TIM0_COMPA Timer/Counter0 compare match A

TIM0_COMPB Timer/Counter0 compare match B

Watchdog time-out

USI START

USI overflow

If the program never enables an interrupt source, the interrupt vectors are not used, and regular program code can be placed at these locations. The most typical and general program setup for the reset and interrupt vector addresses in Atmel

ATtiny25/45/85 is:

Address

0x0000

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

0x0009

0x000A

0x000B

0x000C

0x000D

0x000E

0x000F

0x0010

0x0011

0x0012

0x0013

0x0014

...

...

Labels Code rjmp RESET rjmp EXT_INT0 rjmp PCINT0 rjmp TIM1_COMPA rjmp TIM1_OVF rjmp TIM0_OVF rjmp EE_RDY rjmp ANA_COMP rjmp ADC rjmp TIM1_COMPB rjmp TIM0_COMPA rjmp TIM0_COMPB rjmp WDT rjmp USI_START rjmp USI_OVF

RESET: ldi ldi out out sei

<instr> xxx

...

...

Comments

; Reset Handler

; IRQ0 Handler

; PCINT0 Handler

; Timer1 CompareA Handler

; Timer1 Overflow Handler

; Timer0 Overflow Handler

; EEPROM Ready Handler

; Analog Comparator Handler

; ADC Conversion Handler

; Timer1 CompareB Handler

;

;

;

;

; r16, low(RAMEND); Main program start r17, high(RAMEND); Tiny85 has also SPH

SPL, r16

SPH, r17

; Set Stack Pointer to top of RAM

; Tiny85 has also SPH

; Enable interrupts

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9.

I/O Ports

9.1

Introduction

All AVR

®

ports have true read-modify-write functionality when used as general digital I/O ports. This means that the direction of one port pin can be changed without unintentionally changing the direction of any other pin with the SBI and CBI instructions. The same applies when changing drive value (if configured as output) or enabling/disabling of pull-up resistors

(if configured as input). Each output buffer has symmetrical drive characteristics with both high sink and source capability.

The pin driver is strong enough to drive LED displays directly. All port pins have individually selectable pull-up resistors with a supply-voltage invariant resistance. All I/O pins have protection diodes to both V

CC

and ground as indicated in

Figure 9-1

.

Refer to

Section 21. “Electrical Characteristics” on page 137 for a complete list of parameters.

Figure 9-1. I/O Pin Equivalent Schematic

Pxn

R pu

See Figure

”General Digital I/O” for Details

Logic

All registers and bit references in this section are written in general form. A lower case “x” represents the numbering letter for the port, and a lower case “n” represents the bit number. However, when using the register or bit defines in a program, the precise form must be used. For example, PORTB3 for bit no. 3 in Port B, here documented generally as PORTxn. The

physical I/O registers and bit locations are listed in Section 9.4 “Register Description for I/O-Ports” on page 53 .

Three I/O memory address locations are allocated for each port, one each for the data register – PORTx, data direction register – DDRx, and the port input Pins – PINx. The port input pins I/O location is read only, while the data register and the data direction register are read/write. However, writing a logic one to a bit in the PINx register, will result in a toggle in the corresponding bit in the data register. In addition, the pull-up disable – PUD bit in MCUCR disables the pull-up function for all pins in all ports when set.

Using the I/O port as general digital I/O is described in Section 9.2 “Ports as General Digital I/O” on page 44

. Most port pins are multiplexed with alternate functions for the peripheral features on the device. How each alternate function interferes with

the port pin is described in Section 9.3 “Alternate Port Functions” on page 48 . Refer to the individual module sections for a

full description of the alternate functions.

Note that enabling the alternate function of some of the port pins does not affect the use of the other pins in the port as general digital I/O.

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9.2

Ports as General Digital I/O

The ports are bi-directional I/O ports with optional internal pull-ups.

Figure 9-2

shows a functional description of one

I/O-port pin, here generically called Pxn.

Figure 9-2. General Digital I/O

(1)

PUD

Q

DDxn

D

Q

CLR

RESET

WDx

RDx

Pxn

SLEEP

Q D

PORTxn

Q

CLR

RESET

1

0

RRx

WRx

WPx

RPx

D

L

Synchronizer

Q

Q

D

PINxn

Q

Q

CLK

I/O

PUD:

SLEEP:

CLK

I/O

:

PULLUP DISABLE

SLEEP CONTROL

I/O CLOCK

WDx:

RDx:

WRx:

RRx:

RPx:

WPx:

WRITE DDRx

READ DDRx

WRITE PORTx

READ PORTx REGISTER

READ PORTx PIN

WRITE PINx REGISTER

Note: 1.

WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clk

I/O are common to all ports.

, SLEEP, and PUD

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9.2.1

Configuring the Pin

Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in Section 9.4 “Register Description for

I/O-Ports” on page 53

, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits at the PORTx I/O address, and the PINxn bits at the PINx I/O address.

The DDxn bit in the DDRx register selects the direction of this pin. If DDxn is written logic one, Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input pin.

If PORTxn is written logic one when the pin is configured as an input pin, the pull-up resistor is activated. To switch the pull-up resistor off, PORTxn has to be written logic zero or the pin has to be configured as an output pin. The port pins are tri-stated when reset condition becomes active, even if no clocks are running.

If PORTxn is written logic one when the pin is configured as an output pin, the port pin is driven high (one). If PORTxn is written logic zero when the pin is configured as an output pin, the port pin is driven low (zero).

9.2.2

Toggling the Pin

Writing a logic one to PINxn toggles the value of PORTxn, independent on the value of DDRxn. Note that the SBI instruction can be used to toggle one single bit in a port.

9.2.3

Switching Between Input and Output

When switching between tri-state ({DDxn, PORTxn} = 0b00) and output high ({DDxn, PORTxn} = 0b11), an intermediate state with either pull-up enabled {DDxn, PORTxn} = 0b01) or output low ({DDxn, PORTxn} = 0b10) must occur. Normally, the pull-up enabled state is fully acceptable, as a high-impedant environment will not notice the difference between a strong high driver and a pull-up. If this is not the case, the PUD bit in the MCUCR Register can be set to disable all pull-ups in all ports.

Switching between input with pull-up and output low generates the same problem. The user must use either the tri-state

({DDxn, PORTxn} = 0b00) or the output high state ({DDxn, PORTxn} = 0b10) as an intermediate step.

Table 9-1

summarizes the control signals for the pin value.

Table 9-1.

Port Pin Configurations

DDxn

0

0

0

1

1

PORTxn

0

1

1

0

1

PUD (in MCUCR)

1

X

X

X

0

I/O

Input

Input

Input

Output

Output

Pull-up

No

Yes

No

No

No

Comment

Tri-state (Hi-Z)

Pxn will source current if ext. pulled low.

Tri-state (Hi-Z)

Output low (sink)

Output high (source)

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9.2.4

Reading the Pin Value

Independent of the setting of data direction bit DDxn, the port pin can be read through the PINxn register bit. As shown in

Figure 9-2 on page 44

, the PINxn register bit and the preceding latch constitute a synchronizer. This is needed to avoid

metastability if the physical pin changes value near the edge of the internal clock, but it also introduces a delay. Figure 9-3

shows a timing diagram of the synchronization when reading an externally applied pin value. The maximum and minimum propagation delays are denoted t pd,max

and t pd,min

respectively.

Figure 9-3. Synchronization when Reading an Externally Applied Pin Value

System CLK

Instructions

SYNC Latch

PINxn r17

XXX XXX in r17, PINx

0xFF 0x00 t pd, max t pd, min

Consider the clock period starting shortly after the first falling edge of the system clock. The latch is closed when the clock is low, and goes transparent when the clock is high, as indicated by the shaded region of the “SYNC LATCH” signal. The signal value is latched when the system clock goes low. It is clocked into the PINxn register at the succeeding positive clock edge.

As indicated by the two arrows tpd,max and tpd,min, a single signal transition on the pin will be delayed between ½ and 1½ system clock period depending upon the time of assertion.

When reading back a software assigned pin value, a nop instruction must be inserted as indicated in

Figure 9-4

. The out instruction sets the “SYNC LATCH” signal at the positive edge of the clock. In this case, the delay tpd through the synchronizer is one system clock period.

Figure 9-4. Synchronization when Reading a Software Assigned Pin Value

System CLK r16

Instructions

SYNC Latch

PINxn r17 out PORTx, r16 nop

0xFF in r17, PINx

0x00 t pd

0xFF

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The following code example shows how to set port B pins 0 and 1 high, 2 and 3 low, and define the port pins from 4 to 5 as input with a pull-up assigned to port pin 4. The resulting pin values are read back again, but as previously discussed, a nop instruction is included to be able to read back the value recently assigned to some of the pins.

Assembly Code Example

(1)

...

;

Define pull-ups and set outputs high

;

Define directions for port pins

ldi

r16,(1<<PB4)|(1<<PB1)|(1<<PB0)

ldi out

r17,(1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0)

PORTB,r16

out

DDRB,r17

;

Insert nop for synchronization

nop

;

Read port pins

in

r16,PINB

...

C Code Example

unsigned char

i;

...

/*

Define pull-ups and set outputs high

*/

/*

Define directions for port pins

*/

PORTB = (1<<PB4)|(1<<PB1)|(1<<PB0);

DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);

/*

Insert nop for synchronization

*/

_NOP();

/*

Read port pins

*/ i = PINB;

...

Note: 1.

For the assembly program, two temporary registers are used to minimize the time from pull-ups are set on pins

0, 1 and 4, until the direction bits are correctly set, defining bit 2 and 3 as low and redefining bits 0 and 1 as strong high drivers.

9.2.5

Digital Input Enable and Sleep Modes

As shown in Figure 9-2 , the digital input signal can be clamped to ground at the input of the schmitt-trigger. The signal

denoted SLEEP in the figure, is set by the MCU sleep controller in power-down mode, power-save mode, and standby mode to avoid high power consumption if some input signals are left floating, or have an analog signal level close to V

CC

/2.

SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt request is not enabled, SLEEP is active also for these pins. SLEEP is also overridden by various other alternate functions as described in

Section 9.3

“Alternate Port Functions” on page 48 .

If a logic high level (“one”) is present on an asynchronous external interrupt pin configured as “interrupt on rising edge, falling edge, or any logic change on pin” while the external interrupt is not enabled, the corresponding external interrupt flag will be set when resuming from the above mentioned sleep mode, as the clamping in these sleep mode produces the requested logic change.

9.2.6

Unconnected Pins

If some pins are unused, it is recommended to ensure that these pins have a defined level. Even though most of the digital inputs are disabled in the deep sleep modes as described above, floating inputs should be avoided to reduce current consumption in all other modes where the digital inputs are enabled (reset, active mode and idle mode).

The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up. In this case, the pull-up will be disabled during reset. If low power consumption during reset is important, it is recommended to use an external pull-up or pulldown. Connecting unused pins directly to V

CC the pin is accidentally configured as an output.

or GND is not recommended, since this may cause excessive currents if

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9.3

Alternate Port Functions

Most port pins have alternate functions in addition to being general digital I/Os.

Figure 9-5

shows how the port pin control

signals from the simplified Figure 9-2

can be overridden by alternate functions. The overriding signals may not be present in all port pins, but the figure serves as a generic description applicable to all port pins in the AVR

®

microcontroller family.

Figure 9-5. Alternate Port Functions

(1)

PUOExn

PUOVxn 1

0

PUD

DDOExn

DDOVxn 1

0 Q

DDxn

D

Q

CLR

RESET

WDx

RDx

PVOExn

PVOVxn

Pxn

1

0

1

0

DIEOExn

DIEOVxn

SLEEP

Synchronizer

D SET Q

L

CLR

Q

D

PINxn

Q

CLR

Q

Q D

PORTxn

Q

CLR

RESET

1

0

RRx

WRx

RPx

PTOExn

WPx

CLK

I/O

DIxn

AIOxn

PUOExn:

PUOVxn:

DDOExn:

DDOVxn:

PVOExn:

PVOVxn:

DIEOExn:

DIEOVxn:

SLEEP:

PTOExn:

Pxn PULL-UP OVERRIDE ENABLE

Pxn PULL-UP OVERRIDE VALUE

Pxn DATA DIRECTION OVERRIDE ENABLE

Pxn DATA DIRECTION OVERRIDE VALUE

Pxn PORT VALUE OVERRIDE ENABLE

Pxn PORT VALUE OVERRIDE VALUE

Pxn DIGITAL INPUT ENABLE OVERRIDE ENABLE

Pxn DIGITAL INPUT ENABLE OVERRIDE VALUE

SLEEP CONTROL

Pxn, PORT TOGGLE OVERRIDE ENABLE

PUD:

WDx:

RDx:

RRx:

WRx:

RPx:

WPx:

CLK:

DIxn:

I/O

AIOxn:

PULL-UP DISABLE

WRITE DDRx

READ DDRx

READ PORTx REGISTER

WRITE PORTx

READ PORTx PIN

WRITE PINx

I/O CLOCK

DIGITAL INPUT PIN n ON PORTx

ANALOG INPUT/OUTPUT PIN n ON PORTx

Note: 1.

WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clk

I/O are common to all ports. All other signals are unique for each pin.

, SLEEP, and PUD

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Table 9-2

summarizes the function of the overriding signals. The pin and port indexes from

Figure 9-5 on page 48

are not shown in the succeeding tables. The overriding signals are generated internally in the modules having the alternate function.

Table 9-2.

Generic Description of Overriding Signals for Alternate Functions

Signal Name

PUOE

PUOV

DDOE

DDOV

PVOE

PVOV

PTOE

DIEOE

DIEOV

DI

AIO

Full Name

Pull-up Override Enable

Pull-up override value

Data direction override enable

Data direction override value

Port value override enable

Description

If this signal is set, the pull-up enable is controlled by the PUOV signal. If this signal is cleared, the pull-up is enabled when

{DDxn, PORTxn, PUD} = 0b010.

If PUOE is set, the pull-up is enabled/disabled when PUOV is set/cleared, regardless of the setting of the DDxn, PORTxn, and PUD register bits.

If this signal is set, the output driver enable is controlled by the DDOV signal.

If this signal is cleared, the output driver is enabled by the DDxn register bit.

If DDOE is set, the output driver is enabled/disabled when DDOV is set/cleared, regardless of the setting of the DDxn register bit.

If this signal is set and the output driver is enabled, the port value is controlled by the PVOV signal. If PVOE is cleared, and the output driver is enabled, the port value is controlled by the PORTxn register bit.

Port value override value

If PVOE is set, the port value is set to PVOV, regardless of the setting of the

PORTxn register bit.

Port toggle override enable

If PTOE is set, the PORTxn register bit is inverted.

Digital input enable override enable

Digital input enable

Override value

Digital input

Analog input/output

If this bit is set, the digital Input Enable is controlled by the DIEOV signal. If this signal is cleared, the Digital Input Enable is determined by MCU state

(Normal mode, sleep mode).

If DIEOE is set, the digital input is enabled/disabled when DIEOV is set/cleared, regardless of the MCU state (Normal mode, sleep mode).

This is the digital input to alternate functions. In the figure, the signal is connected to the output of the schmitt-trigger but before the synchronizer.

Unless the digital input is used as a clock source, the module with the alternate function will use its own synchronizer.

This is the analog input/output to/from alternate functions. The signal is connected directly to the pad, and can be used bi-directionally.

The following subsections shortly describe the alternate functions for each port, and relate the overriding signals to the alternate function. Refer to the alternate function description for further details.

9.3.1

MCU Control Register – MCUCR

Bit

Read/Write

Initial Value

7

BODS

R/W

0

6

PUD

R/W

0

5

SE

R/W

0

4

SM1

R/W

0

3

SM0

R/W

0

2 1

BODSE ISC01

R/W

0

R/W

0

0

ISC00

R/W

0

MCUCR

• Bit 6 – PUD: Pull-up Disable

When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn and PORTxn registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01). See

Section 9.2.1 “Configuring the Pin” on page 45 for more

details about this feature.

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9.3.2

Alternate Functions of Port B

The port B pins with alternate function are shown in Table 9-3 .

Table 9-3.

Port B Pins Alternate Functions

Port Pin

PB5

PB4

Alternate Function

RESET / dW / ADC0 / PCINT5

(1)

XTAL2 / CLKO / ADC2 / OC1B / PCINT4

(2)

XTAL1 / ADC3 / OC1B / PCINT3

(3)

PB3

PB2

PB1

SCK / ADC1 / T0 / USCK / SCL / INT0 / PCINT

(4)

MISO / AIN1 / OC0B / OC1A / DO / PCINT1

(4)

PB0 MOSI / AIN0 / OC0A / OC1A / DI / SDA / AREF / PCINT0

Notes: 1.

Reset Pin, debugWIRE I/O, ADC input channel or pin change interrupt.

(6)

2.

XOSC output, divided system clock output, ADC input channel, Timer/Counter1 output compare and PWM output B, or pin change interrupt.

3.

XOSC input / external clock input, ADC input channel, Timer/Counter1 inverted output compare and PWM output B, or pin change interrupt.

4.

Serial clock input, ADC input channel, Timer/Counter clock input, USI clock (three-wire mode), USI clock

(two-wire mode), external interrupt, or pin change interrupt.

5.

Serial data input, analog comparator negative input, Timer/Counter0 output compare and PWM Output B,

Timer/Counter1 output compare and PWM Output A, USI data output (three-wire mode), or pin change interrupt.

6.

Serial data output, analog comparator positive input, Timer/Counter0 output compare and PWM output A,

Timer/Counter1 inverted output compare and PWM output A, USI data Input (three-wire mode), USI Data

(two-wire mode), Voltage Ref., or pin change interrupt.

• Port B, Bit 5 - RESET/dW/ADC0/PCINT5

RESET: External reset input is active low and enabled by unprogramming (“1”) the RSTDISBL fuse. Pull up is activated and output driver and digital input are deactivated when the pin is used as the RESET pin.

dW: When the debugWIRE enable (DWEN) fuse is programmed and lock bits are unprogrammed, the debugWIRE system within the target device is activated. The RESET port pin is configured as a wire-AND (open-drain) bi-directional I/O pin with pull-up enabled and becomes the communication gateway between target and emulator.

ADC0: Analog to digital converter, channel 0.

PCINT5: Pin change interrupt source 5.

• Port B, Bit 4- XTAL2/CLKO/ADC2/OC1B/PCINT4

XTAL2: Chip clock oscillator pin 2. Used as clock pin for all chip clock sources except internal calibrated RC oscillator and external clock. When used as a clock pin, the pin can not be used as an I/O pin. When using internal calibrated RC oscillator or external clock as a chip clock sources, PB4 serves as an ordinary I/O pin.

CLKO: The divided system clock can be output on the pin PB4. The divided system clock will be output if the CKOUT fuse is programmed, regardless of the PORTB4 and DDB4 settings. It will also be output during reset.

ADC2: Analog to digital converter, channel 2.

OC1B: Output compare match output: The PB4 pin can serve as an external output for the Timer/Counter1 compare match

B when configured as an output (DDB4 set). The OC1B pin is also the output pin for the PWM mode timer function.

PCINT4: Pin change interrupt source 4.

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• Port B, Bit 3 - XTAL1/ADC3/OC1B/PCINT3

XTAL1: Chip clock oscillator pin 1. Used for all chip clock sources except internal calibrated RC oscillator. When used as a clock pin, the pin can not be used as an I/O pin.

ADC3: Analog to digital converter, channel 3.

OC1B: Inverted output compare match output: The PB3 pin can serve as an external output for the Timer/Counter1 compare match B when configured as an output (DDB3 set). The OC1B pin is also the inverted output pin for the PWM mode timer function.

PCINT3: Pin change interrupt source 3.

• Port B, Bit 2 - SCK/ADC1/T0/USCK/SCL/INT0/PCINT2

SCK: Master clock output, slave clock input pin for SPI channel. When the SPI is enabled as a slave, this pin is configured as an input regardless of the setting of DDB2. When the SPI is enabled as a master, the data direction of this pin is controlled by DDPB2. When the pin is forced by the SPI to be an input, the pull-up can still be controlled by the PORTB2 bit.

ADC1: Analog to digital converter, channel 1.

T0: Timer/Counter0 counter source.

USCK: Three-wire mode universal serial interface clock.

SCL: Two-wire mode serial clock for USI two-wire mode.

INT0: External interrupt source 0.

PCINT2: Pin change interrupt source 2.

• Port B, Bit 1 - MISO/AIN1/OC0B/OC1A/DO/PCINT1

MISO: Master data input, slave data output pin for SPI channel. When the SPI is enabled as a master, this pin is configured as an input regardless of the setting of DDB1. When the SPI is enabled as a slave, the data direction of this pin is controlled by DDB1. When the pin is forced by the SPI to be an input, the pull-up can still be controlled by the PORTB1 bit.

AIN1: Analog comparator negative input. Configure the port pin as input with the internal pull-up switched off to avoid the digital port function from interfering with the function of the analog comparator.

OC0B: Output compare match output. The PB1 pin can serve as an external output for the Timer/Counter0 compare match

B. The PB1 pin has to be configured as an output (DDB1 set (one)) to serve this function. The OC0B pin is also the output pin for the PWM mode timer function.

OC1A: Output compare match output: The PB1 pin can serve as an external output for the Timer/Counter1 compare match

B when configured as an output (DDB1 set). The OC1A pin is also the output pin for the PWM mode timer function.

DO: Three-wire mode universal serial interface data output. Three-wire mode data output overrides PORTB1 value and it is driven to the port when data direction bit DDB1 is set (one). PORTB1 still enables the pull-up, if the direction is input and

PORTB1 is set (one).

PCINT1: Pin change interrupt source 1.

• Port B, Bit 0 - MOSI/AIN0/OC0A/OC1A/DI/SDA/AREF/PCINT0

MOSI: SPI master data output, slave data input for SPI channel. When the SPI is enabled as a slave, this pin is configured as an input regardless of the setting of DDB0. When the SPI is enabled as a master, the data direction of this pin is controlled by DDB0. When the pin is forced by the SPI to be an input, the pull-up can still be controlled by the PORTB0 bit.

AIN0: Analog comparator positive input. Configure the port pin as input with the internal pull-up switched off to avoid the digital port function from interfering with the function of the analog comparator.

OC0A: Output compare match output. The PB0 pin can serve as an external output for the Timer/Counter0 compare match

A when configured as an output (DDB0 set (one)). The OC0A pin is also the output pin for the PWM mode timer function.

OC1A: Inverted output compare match output: The PB0 pin can serve as an external output for the Timer/Counter1 compare match B when configured as an output (DDB0 set). The OC1A pin is also the inverted output pin for the PWM mode timer function.

SDA: Two-wire mode serial interface data.

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AREF: External analog reference for ADC. Pull up and output driver are disabled on PB0 when the pin is used as an external reference or internal voltage reference with external capacitor at the AREF pin.

DI: Data input in USI three-wire mode. USI three-wire mode does not override normal port functions, so pin must be configure as an input for DI function.

PCINT0: Pin change interrupt source 0.

Table 9-4 and Table 9-5

relate the alternate functions of port B to the overriding signals shown in Figure 9-5 on page 48 .

Table 9-4.

Overriding Signals for Alternate Functions in PB5..PB3

Signal Name PB5/RESET/ADC0/PCINT5

PUOE RSTDISBL

(1)

×

DWEN

(1)

PUOV

DDOE

DDOV

1

RSTDISBL

(1) ×

DWEN

(1) debugWire transmit

PVOE 0

PVOV

PTOE

DIEOE

0

0

RSTDISBL

(1)

+ (PCINT5

×

PCIE

+ ADC0D)

PB4/ADC2/XTAL2/OC1B/PCINT4

0

0

0

0

OC1B enable

OC1B

0

PCINT4

×

PCIE + ADC2D

DIEOV

DI

ADC0D

PCINT5 input

ADC2D

PCINT4 input

AIO RESET input, ADC0 input ADC2 input

Note: 1.

1 when the fuse is “0” (programmed).

PB3/ADC3/XTAL1/_OC1B/PCINT3

0

0

0

0

_OC1B enable

_OC1B

0

PCINT3

ADC3D

×

PCIE + ADC3D

PCINT3 input

ADC3 input

Table 9-5.

Overriding Signals for Alternate Functions in PB3..PB0

Signal

Name

PUOE

PUOV

DDOE

DDOV

PVOE

PVOV

PTOE

DIEOE

DIEOV

DI

AIO

PB2/SCK/ADC1/T0/

USCK/SCL/INT0/PCINT2

0

0

USI_TWO_WIRE

(USI_SCL_HOLD + PORTB2)

×

DDB2

T0/USCK/SCL/INT0/

PCINT2 input

ADC1 input

PB1/MISO/DO/AIN1/

OC1A/OC0B/PCINT1

0

0

0

0

USI_TWO_WIRE

×

DDB2

OC0B enable + OC1A enable +

USI_THREE_WIRE

0 OC0B + OC1A + DO

USITC 0

PCINT2

×

PCIE + ADC1D + USISIE PCINT1

×

PCIE + AIN1D

ADC1D AIN1D

PCINT1 input

Analog comparator negative input

PB0/MOSI/DI/SDA/AIN0/AREF/_O

C1A/OC0A/PCINT0

0

0

USI_TWO_WIRE

(SDA + PORTBO)

×

DDB0

OC0A enable + _OC1A enable +

(USI_TWO_WIRE

OC0A + _OC1A

0

PCINT0

×

PCIE + AIN0D + USISIE

AIN0D

×

DDB0)

DI/SDA/PCINT0 input

Analog comparator positive input

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9.4

Register Description for I/O-Ports

9.4.1

Port B Data Register – PORTB

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5 4 3 2 1 0

PORTB5 PORTB4 PORTB3 PORTB2 PORTB1 PORTB0 PORTB

R/W R/W R/W R/W R/W R/W

0 0 0 0 0 0

9.4.2

Port B Data Direction Register – DDRB

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5

DDB5

R/W

0

4

DDB4

R/W

0

9.4.3

Port B Input Pins Address – PINB

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5

PINB5

R/W

N/A

4

PINB4

R/W

N/A

3

DDB3

R/W

0

3

PINB3

R/W

N/A

2

DDB2

R/W

0

2

PINB2

R/W

N/A

1

DDB1

R/W

0

1

PINB1

R/W

N/A

0

DDB0

R/W

0

0

PINB0

R/W

N/A

DDRB

PINB

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10.

External Interrupts

The external interrupts are triggered by the INT0 pin or any of the PCINT5..0 pins. Observe that, if enabled, the interrupts will trigger even if the INT0 or PCINT5..0 pins are configured as outputs. This feature provides a way of generating a software interrupt. Pin change interrupts PCI will trigger if any enabled PCINT5..0 pin toggles. The PCMSK register control which pins contribute to the pin change interrupts. Pin change interrupts on PCINT5..0 are detected asynchronously. This implies that these interrupts can be used for waking the part also from sleep modes other than idle mode.

The INT0 interrupts can be triggered by a falling or rising edge or a low level. This is set up as indicated in the specification for the MCU control register – MCUCR. When the INT0 interrupt is enabled and is configured as level triggered, the interrupt will trigger as long as the pin is held low. Note that recognition of falling or rising edge interrupts on INT0 requires the

presence of an I/O clock, described in Section 5.1 “Clock Systems and their Distribution” on page 19

. Low level interrupt on

INT0 is detected asynchronously. This implies that this interrupt can be used for waking the part also from sleep modes other than idle mode. The I/O clock is halted in all sleep modes except idle mode.

Note that if a level triggered interrupt is used for wake-up from power-down, the required level must be held long enough for the MCU to complete the wake-up to trigger the level interrupt. If the level disappears before the end of the start-up time, the

MCU will still wake up, but no interrupt will be generated. The start-up time is defined by the SUT and CKSEL fuses as

described in Section 5. “System Clock and Clock Options” on page 19

.

10.1

MCU Control Register – MCUCR

The external interrupt control register A contains control bits for interrupt sense control.

Bit

Read/Write

Initial Value

7

BODS

R/W

0

6

PUD

R/W

0

5

SE

R/W

0

4

SM1

R/W

0

3

SM0

R/W

0

2

BODSE

R/W

0

1

ISC01

R/W

0

0

ISC00

R/W

0

MCUCR

• Bits 1, 0 – ISC01, ISC00: Interrupt Sense Control 0 Bit 1 and Bit 0

The external interrupt 0 is activated by the external pin INT0 if the SREG I-flag and the corresponding interrupt mask are set.

The level and edges on the external INT0 pin that activate the interrupt are defined in Table 10-1

. The value on the INT0 pin is sampled before detecting edges. If edge or toggle interrupt is selected, pulses that last longer than one clock period will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. If low level interrupt is selected, the low level must be held until the completion of the currently executing instruction to generate an interrupt.

Table 10-1. Interrupt 0 Sense Control

ISC01

0

0

1

1

ISC00

0

1

0

1

Description

The low level of INT0 generates an interrupt request.

Any logical change on INT0 generates an interrupt request.

The falling edge of INT0 generates an interrupt request.

The rising edge of INT0 generates an interrupt request.

10.2

General Interrupt Mask Register – GIMSK

Bit

Read/Write

Initial Value

R

0

7

6

INT0

R/W

0

5

PCIE

R/W

0

R

0

4

R

0

3

R

0

2

R

0

1

• Bits 7, 4..0 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

R

0

0

– GIMSK

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• Bit 6 – INT0: External Interrupt Request 0 Enable

When the INT0 bit is set (one) and the I-bit in the status register (SREG) is set (one), the external pin interrupt is enabled.

The interrupt sense control0 bits 1/0 (ISC01 and ISC00) in the MCU control register (MCUCR) define whether the external interrupt is activated on rising and/or falling edge of the INT0 pin or level sensed. Activity on the pin will cause an interrupt request even if INT0 is configured as an output. The corresponding interrupt of external interrupt request 0 is executed from the INT0 interrupt vector.

• Bit 5 – PCIE: Pin Change Interrupt Enable

When the PCIE bit is set (one) and the I-bit in the status register (SREG) is set (one), pin change interrupt is enabled. Any change on any enabled PCINT5..0 pin will cause an interrupt. The corresponding interrupt of pin change interrupt request is executed from the PCI interrupt vector. PCINT5..0 pins are enabled individually by the PCMSK0 register.

10.3

General Interrupt Flag Register – GIFR

Bit

Read/Write

Initial Value

R

0

7

6

INTF0

R/W

0

5

PCIF

R/W

0

R

0

4

R

0

3

R

0

2

R

0

1

R

0

0

– GIFR

• Bits 7, 4..0 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bit 6 – INTF0: External Interrupt Flag 0

When an edge or logic change on the INT0 pin triggers an interrupt request, INTF0 becomes set (one). If the I-bit in SREG and the INT0 bit in GIMSK are set (one), the MCU will jump to the corresponding interrupt vector. The flag is cleared when the interrupt routine is executed. Alternatively, the flag can be cleared by writing a logical one to it. This flag is always cleared when INT0 is configured as a level interrupt.

• Bit 5 – PCIF: Pin Change Interrupt Flag

When a logic change on any PCINT5..0 pin triggers an interrupt request, PCIF becomes set (one). If the I-bit in SREG and the PCIE bit in GIMSK are set (one), the MCU will jump to the corresponding interrupt vector. The flag is cleared when the interrupt routine is executed. Alternatively, the flag can be cleared by writing a logical one to it.

10.4

Pin Change Mask Register – PCMSK

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5 4 3 2 1 0

PCINT5 PCINT4 PCINT3 PCINT2 PCINT1 PCINT0 PCMSK

R/W R/W R/W R/W R/W R/W

1 1 1 1 1 1

• Bits 7, 6 – Res: Reserved Bits

These bits are reserved bits in the Atmel ATtiny25/45/85 and will always read as zero.

• Bits 5..0 – PCINT5..0: Pin Change Enable Mask 5..0

Each PCINT5..0 bit selects whether pin change interrupt is enabled on the corresponding I/O pin. If PCINT5..0 is set and the

PCIE bit in GIMSK is set, pin change interrupt is enabled on the corresponding I/O pin. If PCINT5..0 is cleared, pin change interrupt on the corresponding I/O pin is disabled.

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11.

8-bit Timer/Counter0 with PWM

Timer/Counter0 is a general purpose 8-bit Timer/Counter module, with two independent output compare units, and with

PWM support. It allows accurate program execution timing (event management) and wave generation. The main features are:

Two independent output compare units

Double buffered output compare registers

Clear timer on compare match (auto reload)

Glitch free, phase correct pulse width modulator (PWM)

Variable PWM period

Frequency generator

Three independent interrupt sources (TOV0, OCF0A, and OCF0B)

11.1

Overview

A simplified block diagram of the 8-bit Timer/Counter is shown in

Figure 11-1 . For the actual placement of I/O pins, refer to

Figure 1 on page 2 . CPU accessible I/O registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O

register and bit locations are listed in

Section 11.8 “8-bit Timer/Counter Register Description” on page 66 .

Figure 11-1. 8-bit Timer/Counter Block Diagram

Count

Clear

Direction

Control Logic clk

Tn

TOVn (Int. Req.)

Clock Select

Edge

Detector

Tn

(from Prescaler)

TOP BOTTOM

Timer/Counter

TCNTn

= =

0

=

OCnA (Int. Req.)

Waveform

Generation

OCnA

OCRnA

Fixed

TOP

Value

OCnB (Int. Req.)

Waveform

Generation

OCnB =

OCRnB

TCCRnA TCCRnB

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11.1.1 Registers

The Timer/Counter (TCNT0) and output compare registers (OCR0A and OCR0B) are 8-bit registers. Interrupt request

(abbreviated to Int.Req. in the figure) signals are all visible in the timer interrupt flag register (TIFR). All interrupts are individually masked with the timer interrupt mask register (TIMSK). TIFR and TIMSK are not shown in the figure.

The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on the T0 pin. The clock select logic block controls which clock source and edge the Timer/Counter uses to increment (or decrement) its value. The

Timer/Counter is inactive when no clock source is selected. The output from the clock select logic is referred to as the timer clock (clk

T0

).

The double buffered output compare registers (OCR0A and OCR0B) is compared with the Timer/Counter value at all times.

The result of the compare can be used by the waveform generator to generate a PWM or variable frequency output on the

output compare pins (OC0A and OC0B). See Section 11.4 “Output Compare Unit” on page 58

for details. The compare match event will also set the compare flag (OCF0A or OCF0B) which can be used to generate an output compare interrupt request.

11.1.2 Definitions

Many register and bit references in this section are written in general form. A lower case “n” replaces the Timer/Counter number, in this case 0. A lower case “x” replaces the output compare unit, in this case compare unit A or compare unit B.

However, when using the register or bit defines in a program, the precise form must be used, i.e., TCNT0 for accessing

Timer/Counter0 counter value and so on.

The definitions below are also used extensively throughout the document.

Table 11-1. Definitions

Parameter

BOTTOM

MAX

TOP

Definition

The counter reaches the BOTTOM when it becomes 0x00.

The counter reaches its MAXimum when it becomes 0xFF (decimal 255).

The counter reaches the TOP when it becomes equal to the highest value in the count sequence. The

TOP value can be assigned to be the fixed value 0xFF (MAX) or the value stored in the OCR0A register.

The assignment is dependent on the mode of operation.

11.2

Timer/Counter Clock Sources

The Timer/Counter can be clocked by an internal or an external clock source. The clock source is selected by the clock select logic which is controlled by the clock select (CS02:0) bits located in the Timer/Counter control register (TCCR0B). For

details on clock sources and prescaler, see Section 12. “Timer/Counter Prescaler” on page 72

.

11.3

Counter Unit

The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.

Figure 11-2

shows a block diagram of the counter and its surroundings.

Figure 11-2. Counter Unit Block Diagram

DATA BUS

TOVn

(Int. Req.)

TCNTn count clear direction

Control Logic clk

Tn

Clock Select

Edge

Detector

(from Prescaler)

Tn bottom top

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Signal description (internal signals):

count

Increment or decrement TCNT0 by 1.

direction clear

Select between increment and decrement.

Clear TCNT0 (set all bits to zero).

clk

Tn

top bottom

Timer/Counter clock, referred to as clk

T0

in the following.

Signalize that TCNT0 has reached maximum value.

Signalize that TCNT0 has reached minimum value (zero).

Depending of the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clk

T0 clk

T0

).

can be generated from an external or internal clock source, selected by the clock select bits (CS02:0). When no clock source is selected (CS02:0 = 0) the timer is stopped. However, the TCNT0 value can be accessed by the CPU, regardless of whether clk

T0

is present or not. A CPU write overrides (has priority over) all counter clear or count operations.

The counting sequence is determined by the setting of the WGM01 and WGM00 bits located in the Timer/Counter control register (TCCR0A) and the WGM02 bit located in the Timer/Counter control register B (TCCR0B). There are close connections between how the counter behaves (counts) and how waveforms are generated on the output compare output

OC0A. For more details about advanced counting sequences and waveform generation,

see Section 11.6 “Modes of Operation” on page 61 .

The Timer/Counter overflow flag (TOV0) is set according to the mode of operation selected by the WGM01:0 bits. TOV0 can be used for generating a CPU interrupt.

11.4

Output Compare Unit

The 8-bit comparator continuously compares TCNT0 with the output compare registers (OCR0A and OCR0B). Whenever

TCNT0 equals OCR0A or OCR0B, the comparator signals a match. A match will set the output compare flag (OCF0A or

OCF0B) at the next timer clock cycle. If the corresponding interrupt is enabled, the output compare flag generates an output compare interrupt. The output compare flag is automatically cleared when the interrupt is executed. Alternatively, the flag can be cleared by software by writing a logical one to its I/O bit location. The waveform generator uses the match signal to generate an output according to operating mode set by the WGM02:0 bits and compare output mode (COM0x1:0) bits. The max and bottom signals are used by the waveform generator for handling the special cases of the extreme values in some

modes of operation (see Section 11.6 “Modes of Operation” on page 61

).

Figure 11-3 shows a block diagram of the output compare unit.

Figure 11-3. Output Compare Unit, Block Diagram

DATA BUS

OCRnx TCNTn

=

(8-bit Comparator)

OCFnx (Int. Req.) top bottom

FOCn

Waveform Generator

OCnx

WGMn1:0 COMnx1:0

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The OCR0x registers are double buffered when using any of the pulse width modulation (PWM) modes. For the normal and clear timer on compare (CTC) modes of operation, the double buffering is disabled. The double buffering synchronizes the update of the OCR0x compare registers to either top or bottom of the counting sequence. The synchronization prevents the occurrence of odd-length, non-symmetrical PWM pulses, thereby making the output glitch-free.

The OCR0x register access may seem complex, but this is not case. When the double buffering is enabled, the CPU has access to the OCR0x buffer register, and if double buffering is disabled the CPU will access the OCR0x directly.

11.4.1 Force Output Compare

In non-PWM waveform generation modes, the match output of the comparator can be forced by writing a one to the force output compare (FOC0x) bit. Forcing compare match will not set the OCF0x flag or reload/clear the timer, but the OC0x pin will be updated as if a real compare match had occurred (the COM0x1:0 bits settings define whether the OC0x pin is set, cleared or toggled).

11.4.2 Compare Match Blocking by TCNT0 Write

All CPU write operations to the TCNT0 register will block any compare match that occur in the next timer clock cycle, even when the timer is stopped. This feature allows OCR0x to be initialized to the same value as TCNT0 without triggering an interrupt when the Timer/Counter clock is enabled.

11.4.3 Using the Output Compare Unit

Since writing TCNT0 in any mode of operation will block all compare matches for one timer clock cycle, there are risks involved when changing TCNT0 when using the output compare unit, independently of whether the Timer/Counter is running or not. If the value written to TCNT0 equals the OCR0x value, the compare match will be missed, resulting in incorrect waveform generation. Similarly, do not write the TCNT0 value equal to BOTTOM when the counter is down-counting.

The setup of the OC0x should be performed before setting the data direction register for the port pin to output. The easiest way of setting the OC0x value is to use the force output compare (FOC0x) strobe bits in normal mode. The OC0x registers keep their values even when changing between waveform generation modes.

Be aware that the COM0x1:0 bits are not double buffered together with the compare value. Changing the COM0x1:0 bits will take effect immediately.

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11.5

Compare Match Output Unit

The compare output mode (COM0x1:0) bits have two functions. The waveform generator uses the COM0x1:0 bits for defining the output compare (OC0x) state at the next compare match. Also, the COM0x1:0 bits control the OC0x pin output source.

Figure 11-4 on page 60 shows a simplified schematic of the logic affected by the COM0x1:0 bit setting. The I/O

registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the general I/O port control registers (DDR and PORT) that are affected by the COM0x1:0 bits are shown. When referring to the OC0x state, the reference is for the internal OC0x register, not the OC0x pin. If a system reset occur, the OC0x register is reset to “0”.

Figure 11-4. Compare Match Output Unit, Schematic

COMnx1

COMnx0

FOCn

Waveform

Generator

D Q

OCnx

D Q

D

PORT

Q

1

0

OCn

Pin

DDR clk

I/O

The general I/O port function is overridden by the output compare (OC0x) from the waveform generator if either of the

COM0x1:0 bits are set. However, the OC0x pin direction (input or output) is still controlled by the data direction register

(DDR) for the port pin. The Data direction register bit for the OC0x pin (DDR_OC0x) must be set as output before the OC0x value is visible on the pin. The port override function is independent of the waveform generation mode.

The design of the output compare pin logic allows initialization of the OC0x state before the output is enabled. Note that some COM0x1:0 bit settings are reserved for certain modes of operation. See

Section 11.8 “8-bit Timer/Counter Register

Description” on page 66

11.5.1 Compare Output Mode and Waveform Generation

The waveform generator uses the COM0x1:0 bits differently in normal, CTC, and PWM modes. For all modes, setting the

COM0x1:0 = 0 tells the waveform generator that no action on the OC0x register is to be performed on the next compare match. For compare output actions in the non-PWM modes refer to

Table 11-2 on page 66

. For fast PWM mode, refer to

Table 11-3 on page 67 , and for phase correct PWM refer to Table 11-4 on page 67 .

A change of the COM0x1:0 bits state will have effect at the first compare match after the bits are written. For non-PWM modes, the action can be forced to have immediate effect by using the FOC0x strobe bits.

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11.6

Modes of Operation

The mode of operation, i.e., the behavior of the Timer/Counter and the output compare pins, is defined by the combination of the waveform generation mode (WGM02:0) and compare output mode (COM0x1:0) bits. The compare output mode bits do not affect the counting sequence, while the waveform generation mode bits do. The COM0x1:0 bits control whether the

PWM output generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes the COM0x1:0 bits

control whether the output should be set, cleared, or toggled at a compare match (see Section 11.5 “Compare Match Output

Unit” on page 60

).

For detailed timing information refer to

Figure 11-8 on page 65 , Figure 11-9 on page 65 , Figure 11-10 on page 65 and

Figure 11-11 on page 66

in Section 11.7 “Timer/Counter Timing Diagrams” on page 65 .

11.6.1 Normal Mode

The simplest mode of operation is the normal mode (WGM02:0 = 0). In this mode the counting direction is always up

(incrementing), and no counter clear is performed. The counter simply overruns when it passes its maximum 8-bit value

(TOP = 0xFF) and then restarts from the bottom (0x00). In normal operation the Timer/Counter overflow flag (TOV0) will be set in the same timer clock cycle as the TCNT0 becomes zero. The TOV0 flag in this case behaves like a ninth bit, except that it is only set, not cleared. However, combined with the timer overflow interrupt that automatically clears the TOV0 flag, the timer resolution can be increased by software. There are no special cases to consider in the normal mode, a new counter value can be written anytime.

The output compare unit can be used to generate interrupts at some given time. Using the output compare to generate waveforms in normal mode is not recommended, since this will occupy too much of the CPU time.

11.6.2 Clear Timer on Compare Match (CTC) Mode

In clear timer on compare or CTC mode (WGM02:0 = 2), the OCR0A register is used to manipulate the counter resolution. In

CTC mode the counter is cleared to zero when the counter value (TCNT0) matches the OCR0A. The OCR0A defines the top value for the counter, hence also its resolution. This mode allows greater control of the compare match output frequency. It also simplifies the operation of counting external events.

The timing diagram for the CTC mode is shown in Figure 11-5 on page 61

. The counter value (TCNT0) increases until a compare match occurs between TCNT0 and OCR0A, and then counter (TCNT0) is cleared.

Figure 11-5. CTC Mode, Timing Diagram

OCnx Interrupt Flag Set

TCNTn

OCn

(Toggle)

Period

1 2 3 4

(COMnx1:0 = 1)

An interrupt can be generated each time the counter value reaches the TOP value by using the OCF0A flag. If the interrupt is enabled, the interrupt handler routine can be used for updating the TOP value. However, changing TOP to a value close to

BOTTOM when the counter is running with none or a low prescaler value must be done with care since the CTC mode does not have the double buffering feature. If the new value written to OCR0A is lower than the current value of TCNT0, the counter will miss the compare match. The counter will then have to count to its maximum value (0xFF) and wrap around starting at 0x00 before the compare match can occur.

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For generating a waveform output in CTC mode, the OC0A output can be set to toggle its logical level on each compare match by setting the compare output mode bits to toggle mode (COM0A1:0 = 1). The OC0A value will not be visible on the f port pin unless the data direction for the pin is set to output. The waveform generated will have a maximum frequency of

OC0

= f clk_I/O

/2 when OCR0A is set to zero (0x00). The waveform frequency is defined by the following equation: f

OCnx

=

× ( clk_I/O

)

The N variable represents the prescale factor (1, 8, 64, 256, or 1024).

As for the normal mode of operation, the TOV0 flag is set in the same timer clock cycle that the counter counts from MAX to

0x00.

11.6.3 Fast PWM Mode

The fast pulse width modulation or fast PWM mode (WGM02:0 = 3 or 7) provides a high frequency PWM waveform generation option. The fast PWM differs from the other PWM option by its single-slope operation. The counter counts from

BOTTOM to TOP then restarts from BOTTOM. TOP is defined as 0xFF when WGM2:0 = 3, and OCR0A when WGM2:0 = 7.

In non-inverting compare output mode, the output compare (OC0x) is cleared on the compare match between TCNT0 and

OCR0x, and set at BOTTOM. In inverting compare output mode, the output is set on compare match and cleared at

BOTTOM. Due to the single-slope operation, the operating frequency of the fast PWM mode can be twice as high as the phase correct PWM mode that use dual-slope operation.

This high frequency makes the fast PWM mode well suited for power regulation, rectification, and DAC applications. High frequency allows physically small sized external components (coils, capacitors), and therefore reduces total system cost.

In fast PWM mode, the counter is incremented until the counter value matches the TOP value. The counter is then cleared at

the following timer clock cycle. The timing diagram for the fast PWM mode is shown in Figure 11-6 on page 62

. The TCNT0 value is in the timing diagram shown as a histogram for illustrating the single-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent compare matches between OCR0x and TCNT0.

Figure 11-6. Fast PWM Mode, Timing Diagram

OCRnx Interrupt

Flag Set

OCRnx Update and

TOVn Interrupt Flag Set

TCNTn

OCn

OCn

Period

1 2 3 4 5 6 7

(COMnx1:0 = 2)

(COMnx1:0 = 3)

The Timer/Counter overflow flag (TOV0) is set each time the counter reaches TOP. If the interrupt is enabled, the interrupt handler routine can be used for updating the compare value.

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In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins. Setting the COM0x1:0 bits to two will produce a non-inverted PWM and an inverted PWM output can be generated by setting the COM0x1:0 to three:

Setting the COM0A1:0 bits to one allows the AC0A pin to toggle on compare matches if the WGM02 bit is set. This option is not available for the OC0B pin (See

Table 11-3 on page 67 ). The actual OC0x value will only be visible on the port pin if the

data direction for the port pin is set as output. The PWM waveform is generated by setting (or clearing) the OC0x register at the compare match between OCR0x and TCNT0, and clearing (or setting) the OC0x register at the timer clock cycle the counter is cleared (changes from TOP to BOTTOM).

The PWM frequency for the output can be calculated by the following equation: f

OCnxPWM

= f clk_I/O

N 256

The N variable represents the prescale factor (1, 8, 64, 256, or 1024).

The extreme values for the OCR0A register represents special cases when generating a PWM waveform output in the fast

PWM mode. If the OCR0A is set equal to BOTTOM, the output will be a narrow spike for each MAX+1 timer clock cycle.

Setting the OCR0A equal to MAX will result in a constantly high or low output (depending on the polarity of the output set by the COM0A1:0 bits.)

A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by setting OC0x to toggle its logical level on each compare match (COM0x1:0 = 1). The waveform generated will have a maximum frequency of f

OC0

= f clk_I/O

/2 when OCR0A is set to zero. This feature is similar to the OC0A toggle in CTC mode, except the double buffer feature of the output compare unit is enabled in the fast PWM mode.

11.6.4 Phase Correct PWM Mode

The phase correct PWM mode (WGM02:0 = 1 or 5) provides a high resolution phase correct PWM waveform generation option. The phase correct PWM mode is based on a dual-slope operation. The counter counts repeatedly from BOTTOM to

TOP and then from TOP to BOTTOM. TOP is defined as 0xFF when WGM2:0 = 1, and OCR0A when WGM2:0 = 5.

In non-inverting compare output mode, the output compare (OC0x) is cleared on the compare match between TCNT0 and

OCR0x while up counting, and set on the compare match while down-counting. In inverting output compare mode, the operation is inverted. The dual-slope operation has lower maximum operation frequency than single slope operation.

However, due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control applications.

In phase correct PWM mode the counter is incremented until the counter value matches TOP. When the counter reaches

TOP, it changes the count direction. The TCNT0 value will be equal to TOP for one timer clock cycle. The timing diagram for

the phase correct PWM mode is shown on Figure 11-7 on page 64 . The TCNT0 value is in the timing diagram shown as a

histogram for illustrating the dual-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent compare matches between OCR0x and TCNT0.

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Figure 11-7. Phase Correct PWM Mode, Timing Diagram

OCnx Interrupt

Flag Set

OCRnx Update

TOVn Interrupt

Flag Set

TCNTn

OCn

OCn

Period

1 2 3

(COMnx1:0 = 2)

(COMnx1:0 = 3)

The Timer/Counter overflow flag (TOV0) is set each time the counter reaches BOTTOM. The interrupt flag can be used to generate an interrupt each time the counter reaches the BOTTOM value.

In phase correct PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins. Setting the

COM0x1:0 bits to two will produce a non-inverted PWM. An inverted PWM output can be generated by setting the

COM0x1:0 to three: Setting the COM0A0 bits to one allows the OC0A pin to toggle on compare matches if the WGM02 bit is set. This option is not available for the OC0B pin (See

Table 11-4 on page 67 ). The actual OC0x value will only be visible on

the port pin if the data direction for the port pin is set as output. The PWM waveform is generated by clearing (or setting) the

OC0x register at the compare match between OCR0x and TCNT0 when the counter increments, and setting (or clearing) the

OC0x register at compare match between OCR0x and TCNT0 when the counter decrements. The PWM frequency for the output when using phase correct PWM can be calculated by the following equation: f

OCnxPCPWM

= f clk_I/O

N 510

The N variable represents the prescale factor (1, 8, 64, 256, or 1024).

The extreme values for the OCR0A register represent special cases when generating a PWM waveform output in the phase correct PWM mode. If the OCR0A is set equal to BOTTOM, the output will be continuously low and if set equal to MAX the output will be continuously high for non-inverted PWM mode. For inverted PWM the output will have the opposite logic values.

At the very start of period 2 in Figure 11-7 on page 64

OCn has a transition from high to low even though there is no compare match. The point of this transition is to guaratee symmetry around BOTTOM. There are two cases that give a transition without compare match.

OCR0A changes its value from MAX, like in

Figure 11-7 on page 64 . When the OCR0A value is MAX the OCn pin

value is the same as the result of a down-counting compare match. To ensure symmetry around BOTTOM the OCn value at MAX must correspond to the result of an up-counting compare match.

The timer starts counting from a value higher than the one in OCR0A, and for that reason misses the compare match and hence the OCn change that would have happened on the way up.

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11.7

Timer/Counter Timing Diagrams

The Timer/Counter is a synchronous design and the timer clock (clk

T0

) is therefore shown as a clock enable signal in the following figures. The figures include information on when interrupt flags are set.

Figure 11-8 contains timing data for basic

Timer/Counter operation. The figure shows the count sequence close to the MAX value in all modes other than phase correct PWM mode.

Figure 11-8. Timer/Counter Timing Diagram, no Prescaling

clk

I/O clk

Tn

(clk

I/O

/1)

TCNTn MAX - 1 MAX BOTTOM BOTTOM + 1

TOVn

Figure 11-9 shows the same timing data, but with the prescaler enabled.

Figure 11-9. Timer/Counter Timing Diagram, with Prescaler (f clk_I/O

/8)

clk

I/O clk

Tn

(clk

I/O

/8)

TCNTn MAX - 1 MAX BOTTOM

TOVn

BOTTOM + 1

Figure 11-10

shows the setting of OCF0B in all modes and OCF0A in all modes except CTC mode and PWM mode, where

OCR0A is TOP.

Figure 11-10. Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (f clk_I/O

/8)

clk

I/O clk

Tn

(clk

I/O

/8)

TCNTn OCRnx - 1 OCRnx OCRnx + 1 OCRnx + 2

OCRnx Value OCRnx

OCFnx

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Figure 11-11

shows the setting of OCF0A and the clearing of TCNT0 in CTC mode and fast PWM mode where OCR0A is

TOP.

Figure 11-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Prescaler (f clk_I/O

/8)

clk

I/O clk

Tn

(clk

I/O

/8)

TCNTn

(CTC)

TOP - 1 TOP BOTTOM BOTTOM + 1

OCRnx

TOP

OCFnx

11.8

8-bit Timer/Counter Register Description

11.8.1 Timer/Counter Control Register A – TCCR0A

Bit

Read/Write

Initial Value

7 6 5 4

COM0A1 COM0A0 COM0B1 COM0B0

R/W

0

R/W

0

R/W

0

R/W

0

R

0

3

R

0

2

1 0

WGM01 WGM00

TCCR0A

R/W

0

R/W

0

• Bits 7:6 – COM01A:0: Compare Match Output A Mode

These bits control the output compare pin (OC0A) behavior. If one or both of the COM0A1:0 bits are set, the OC0A output overrides the normal port functionality of the I/O pin it is connected to. However, note that the data direction register (DDR) bit corresponding to the OC0A pin must be set in order to enable the output driver.

When OC0A is connected to the pin, the function of the COM0A1:0 bits depends on the WGM02:0 bit setting. Table 11-2

shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to a normal or CTC mode (non-PWM).

Table 11-2. Compare Output Mode, non-PWM Mode

COM01

0

0

1

1

COM00

0

1

0

1

Description

Normal port operation, OC0A disconnected.

Toggle OC0A on compare match

Clear OC0A on compare match

Set OC0A on compare match

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Table 11-3 shows the COM0A1:0 bit functionality when the WGM01:0 bits are set to fast PWM mode.

Table 11-3. Compare Output Mode, Fast PWM Mode

(1)

COM01

0

0

COM00

0

1

Description

Normal port operation, OC0A disconnected.

WGM02 = 0: Normal Port Operation, OC0A disconnected.

WGM02 = 1: Toggle OC0A on compare match.

1 0 Clear OC0A on compare match, set OC0A at TOP

1 1 Set OC0A on compare match, clear OC0A at TOP

Note: 1.

A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case, the compare match is

ignored, but the set or clear is done at TOP. See Section 11.6.3 “Fast PWM Mode” on page 62

for more details.

Table 11-4 shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to phase correct PWM mode.

Table 11-4. Compare Output Mode, Phase Correct PWM Mode

(1)

COM0A1 COM0A0 Description

0

0

0

1

Normal port operation, OC0A disconnected.

WGM02 = 0: Normal port operation, OC0A disconnected.

WGM02 = 1: Toggle OC0A on compare match.

1 0

Clear OC0A on compare match when up-counting. Set OC0A on compare match when down-counting.

1 1

Set OC0A on compare match when up-counting. Clear OC0A on compare match when down-counting.

Note: 1.

A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case, the compare match is

ignored, but the set or clear is done at TOP. See Section 11.6.4 “Phase Correct PWM Mode” on page 63

for more details.

• Bits 5:4 – COM0B1:0: Compare Match Output B Mode

These bits control the output compare pin (OC0B) behavior. If one or both of the COM0B1:0 bits are set, the OC0B output overrides the normal port functionality of the I/O pin it is connected to. However, note that the data direction register (DDR) bit corresponding to the OC0B pin must be set in order to enable the output driver.

When OC0B is connected to the pin, the function of the COM0B1:0 bits depends on the WGM02:0 bit setting.

Table 11-2 shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to a normal or CTC mode (non-PWM).

Table 11-5. Compare Output Mode, non-PWM Mode

COM01

0

0

1

1

COM00

0

1

0

1

Description

Normal port operation, OC0B disconnected.

Toggle OC0B on compare match

Clear OC0B on compare match

Set OC0B on compare match

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Table 11-3 on page 67 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to fast PWM mode.

Table 11-6. Compare Output Mode, Fast PWM Mode

(1)

COM01

0

0

COM00

0

1

Description

Normal port operation, OC0B disconnected.

Reserved

1 0 Clear OC0B on compare match, set OC0B at TOP

1 1 Set OC0B on compare match, clear OC0B at TOP

Note: 1.

A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the compare match is

ignored, but the set or clear is done at TOP. See Section 11.6.3 “Fast PWM Mode” on page 62

for more details.

Table 11-4 on page 67 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to phase correct PWM mode.

Table 11-7. Compare Output Mode, Phase Correct PWM Mode

(1)

COM0A1

0

COM0A0

0

Description

Normal port operation, OC0B disconnected.

0

1

1

0

Reserved

Clear OC0B on compare match when up-counting. Set OC0B on compare match when down-counting.

1 1

Set OC0B on compare match when up-counting. Clear OC0B on compare match when down-counting.

Note: 1.

A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the compare match is

ignored, but the set or clear is done at TOP. See Section 11.6.4 “Phase Correct PWM Mode” on page 63

for more details.

• Bits 3, 2 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bits 1:0 – WGM01:0: Waveform Generation Mode

Combined with the WGM02 bit found in the TCCR0B Register, these bits control the counting sequence of the counter, the source for maximum (TOP) counter value, and what type of waveform generation to be used, see

Table 11-8 on page 68 .

Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), clear timer on compare match (CTC) mode, and two types of pulse width modulation (PWM) modes (see

Section 11.6 “Modes of Operation” on page 61 ).

Table 11-8. Waveform Generation Mode Bit Description

Mode

0

1

4

5

2

3

WGM2

0

0

0

0

1

1

WGM1

0

0

1

1

0

0

6 1 1

7 1 1

Notes: 1.

MAX = 0xFF

2.

BOTTOM = 0x00

WGM0

0

1

0

1

0

1

0

1

Timer/Counter Mode of

Operation

Normal

PWM, phase correct

CTC

Fast PWM

Reserved

PWM, phase correct

Reserved

Fast PWM

TOP

0xFF

0xFF

OCRA

0xFF

OCRA

OCRA

Update of

OCRx at

Immediate

TOP

Immediate

TOP

TOP

TOP

TOV Flag

Set on

MAX

BOTTOM

MAX

MAX

BOTTOM

TOP

(1)(2)

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11.8.2 Timer/Counter Control Register B – TCCR0B

Bit

Read/Write

Initial Value

7

FOC0A

W

0

6

FOC0B

W

0

5

R

0

4

R

0

3

WGM02

R/W

0

2

CS02

R/W

0

1

CS01

R/W

0

0

CS00

R/W

0

TCCR0B

• Bit 7 – FOC0A: Force Output Compare A

The FOC0A bit is only active when the WGM bits specify a non-PWM mode.

However, for ensuring compatibility with future devices, this bit must be set to zero when TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0A bit, an immediate compare match is forced on the waveform generation unit. The OC0A output is changed according to its COM0A1:0 bits setting. Note that the FOC0A bit is implemented as a strobe. Therefore it is the value present in the COM0A1:0 bits that determines the effect of the forced compare.

A FOC0A strobe will not generate any interrupt, nor will it clear the timer in CTC mode using OCR0A as TOP.

The FOC0A bit is always read as zero.

• Bit 6 – FOC0B: Force Output Compare B

The FOC0B bit is only active when the WGM bits specify a non-PWM mode.

However, for ensuring compatibility with future devices, this bit must be set to zero when TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0B bit, an immediate compare match is forced on the waveform generation unit. The OC0B output is changed according to its COM0B1:0 bits setting. Note that the FOC0B bit is implemented as a strobe. Therefore it is the value present in the COM0B1:0 bits that determines the effect of the forced compare.

A FOC0B strobe will not generate any interrupt, nor will it clear the timer in CTC mode using OCR0B as TOP.

The FOC0B bit is always read as zero.

• Bits 5:4 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bit 3 – WGM02: Waveform Generation Mode

See the description in the

Section 11.8.1 “Timer/Counter Control Register A – TCCR0A” on page 66

.

• Bits 2:0 – CS02:0: Clock Select

The three clock select bits select the clock source to be used by the Timer/Counter.

Table 11-9. Clock Select Bit Description

1

1

0

1

1

CS02

0

0

0

CS01

0

0

1

1

0

0

1

1

CS00 Description

0 No clock source (Timer/Counter stopped)

1

0

1

0

1

0

1 clk clk

I/O

I/O

/(no prescaling)

/8 (from prescaler) clk

I/O

/64 (from prescaler) clk

I/O

/256 (from prescaler) clk

I/O

/1024 (from prescaler)

External clock source on T0 pin. Clock on falling edge.

External clock source on T0 pin. Clock on rising edge.

If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the counter even if the pin is configured as an output. This feature allows software control of the counting.

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11.8.3 Timer/Counter Register – TCNT0

Bit

Read/Write

Initial Value

7

R/W

0

6

R/W

0

5

R/W

0

4 3

TCNT0[7:0]

R/W R/W

0 0

2

R/W

0

1

R/W

0

0

R/W

0

TCNT0

The Timer/Counter register gives direct access, both for read and write operations, to the Timer/Counter unit 8-bit counter. writing to the TCNT0 register blocks (removes) the compare match on the following timer clock. Modifying the counter

(TCNT0) while the counter is running, introduces a risk of missing a compare match between TCNT0 and the OCR0x registers.

11.8.4 Output Compare Register A – OCR0A

Bit

Read/Write

Initial Value

7

R/W

0

6

R/W

0

5

R/W

0

4 3

OCR0A[7:0]

R/W R/W

0 0

2

R/W

0

1

R/W

0

0

R/W

0

OCR0A

The output compare register A contains an 8-bit value that is continuously compared with the counter value (TCNT0). A match can be used to generate an output compare interrupt, or to generate a waveform output on the OC0A pin.

11.8.5 Output Compare Register B – OCR0B

Bit

Read/Write

Initial Value

7

R/W

0

6

R/W

0

5

R/W

0

4 3

OCR0B[7:0]

R/W R/W

0 0

2

R/W

0

1

R/W

0

0

R/W

0

OCR0B

The output compare register B contains an 8-bit value that is continuously compared with the counter value (TCNT0). A match can be used to generate an output compare interrupt, or to generate a waveform output on the OC0B pin.

11.8.6 Timer/Counter Interrupt Mask Register – TIMSK

Bit

Read/Write

Initial Value

R

0

7

6 5 4 3

OCIE1A OCIE1B OCIE0A OCIE0B

R

0

R

0

R

0

R/W

0

2

TOIE1

R/W

0

1

TOIE0

R/W

0

R

0

0

– TIMSK

• Bits 7..4, 0 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bit 3 – OCIE0B: Timer/Counter Output Compare Match B Interrupt Enable

When the OCIE0B bit is written to one, and the I-bit in the status register is set, the Timer/Counter compare match B interrupt is enabled. The corresponding interrupt is executed if a compare match in Timer/Counter occurs, i.e., when the OCF0B bit is set in the Timer/Counter interrupt flag register – TIFR0.

• Bit 2 – OCIE0A: Timer/Counter0 Output Compare Match A Interrupt Enable

When the OCIE0A bit is written to one, and the I-bit in the status register is set, the Timer/Counter0 compare match A interrupt is enabled. The corresponding interrupt is executed if a compare match in Timer/Counter0 occurs, i.e., when the

OCF0A bit is set in the Timer/Counter 0 interrupt flag register – TIFR0.

• Bit 1 – TOIE0: Timer/Counter0 Overflow Interrupt Enable

When the TOIE0 bit is written to one, and the I-bit in the status register is set, the Timer/Counter0 overflow interrupt is enabled. The corresponding interrupt is executed if an overflow in Timer/Counter0 occurs, i.e., when the TOV0 bit is set in the Timer/Counter 0 interrupt flag register – TIFR0.

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11.8.7 Timer/Counter 0 Interrupt Flag Register – TIFR

Bit

Read/Write

Initial Value

7

R

0

6 5 4 3

OCF1A OCF1B OCF0A OCF0B

R/W R/W R/W R/W

0 0 0 0

2

TOV1

R/W

0

1

TOV0

R/W

0

0

R

0

TIFR

• Bits 7, 0 – Res: Reserved Bits

These bits are reserved bits in the Atmel ATtiny25/45/85 and will always read as zero.

• Bit 4– OCF0A: Output Compare Flag 0 A

The OCF0A bit is set when a compare match occurs between the Timer/Counter0 and the data in OCR0A – output compare register0. OCF0A is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, OCF0A is cleared by writing a logic one to the flag. When the I-bit in SREG, OCIE0A (Timer/Counter0 compare match interrupt enable), and OCF0A are set, the Timer/Counter0 compare match interrupt is executed.

• Bit 3 – OCF0B: Output Compare Flag 0 B

The OCF0B bit is set when a compare match occurs between the Timer/Counter and the data in OCR0B – output compare register0 B. OCF0B is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively,

OCF0B is cleared by writing a logic one to the flag. When the I-bit in SREG, OCIE0B (Timer/Counter compare B match interrupt enable), and OCF0B are set, the Timer/Counter compare match interrupt is executed.

• Bit 1 – TOV0: Timer/Counter0 Overflow Flag

The bit TOV0 is set when an overflow occurs in Timer/Counter0. TOV0 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, TOV0 is cleared by writing a logic one to the flag. When the

SREG I-bit, TOIE0 (Timer/Counter0 overflow interrupt enable), and TOV0 are set, the Timer/Counter0 overflow interrupt is executed.

The setting of this flag is dependent of the WGM02:0 bit setting. Refer to Table 11-8 on page 68

,

Section 11-8 “Waveform

Generation Mode Bit Description” on page 68

.

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12.

Timer/Counter Prescaler

The Timer/Counter can be clocked directly by the system clock (by setting the CSn2:0 = 1). This provides the fastest f operation, with a maximum Timer/Counter clock frequency equal to system clock frequency (f

CLK_I/O

). Alternatively, one of four taps from the prescaler can be used as a clock source. The prescaled clock has a frequency of either f

CLK_I/O

CLK_I/O

/64, f

CLK_I/O

/256, or f

CLK_I/O

/1024.

/8,

12.1

Prescaler Reset

The prescaler is free running, i.e., operates independently of the clock select logic of the Timer/Counter. Since the prescaler is not affected by the Timer/Counter’s clock select, the state of the prescaler will have implications for situations where a prescaled clock is used. One example of prescaling artifacts occurs when the timer is enabled and clocked by the prescaler

(6 > CSn2:0 > 1). The number of system clock cycles from when the timer is enabled to the first count occurs can be from 1 to N+1 system clock cycles, where N equals the prescaler divisor (8, 64, 256, or 1024).

It is possible to use the prescaler reset for synchronizing the Timer/Counter to program execution.

12.2

External Clock Source

An external clock source applied to the T0 pin can be used as Timer/Counter clock (clk

T0

). The T0 pin is sampled once every system clock cycle by the pin synchronization logic. The synchronized (sampled) signal is then passed through the edge

detector. Figure 12-1

shows a functional equivalent block diagram of the T0 synchronization and edge detector logic. The registers are clocked at the positive edge of the internal system clock (clk

I/O the internal system clock.

). The latch is transparent in the high period of

The edge detector generates one clk

T0

pulse for each positive (CSn2:0 = 7) or negative (CSn2:0 = 6) edge it detects.

Figure 12-1. T0 Pin Sampling

Tn D Q

LE

D Q D Q

Tn_sync

(to Clock

Select Logic) clk

I/O

Synchronization Edge Detector

The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system clock cycles from an edge has been applied to the T0 pin to the counter is updated.

Enabling and disabling of the clock input must be done when T0 has been stable for at least one system clock cycle, otherwise it is a risk that a false Timer/Counter clock pulse is generated.

Each half period of the external clock applied must be longer than one system clock cycle to ensure correct sampling. The external clock must be guaranteed to have less than half the system clock frequency (f

ExtClk

< f clk_I/O

/2) given a 50/50% duty cycle. Since the edge detector uses sampling, the maximum frequency of an external clock it can detect is half the sampling frequency (nyquist sampling theorem). However, due to variation of the system clock frequency and duty cycle caused by oscillator source (crystal, resonator, and capacitors) tolerances, it is recommended that maximum frequency of an external clock source is less than f clk_I/O

/2.5.

An external clock source can not be prescaled.

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Figure 12-2. Prescaler for Timer/Counter0

clk

I/O

Clear

PSR10

10-bit T/C Prescaler

T0 Synchronization

0

CS00

CS01

CS02

Timer/Counter 0 Clock Source clk

T0

Note: 1.

The synchronization logic on the input pins (T0) is shown in Figure 12-1

.

12.2.1 General Timer/Counter Control Register – GTCCR

Bit

Read/Write

Initial Value

7

TSM

R/W

0

6 5 4 3 2 1

PWM1B COM1B1 COM1B0 FOC1B FOC1A PSR1

R

0

R

0

R

0

R

0

R

0

R

0

0

PSR0 GTCCR

R/W

0

• Bit 7 – TSM: Timer/Counter Synchronization Mode

Writing the TSM bit to one activates the Timer/Counter synchronization mode. In this mode, the value that is written to the

PSR0 bit is kept, hence keeping the prescaler reset signal asserted. This ensures that the Timer/Counter is halted and can be configured without the risk of advancing during configuration. When the TSM bit is written to zero, the PSR0 bit is cleared by hardware, and the Timer/Counter start counting.

• Bit 0 – PSR0: Prescaler Reset Timer/Counter0

When this bit is one, the Timer/Counter0 prescaler will be reset. This bit is normally cleared immediately by hardware, except if the TSM bit is set.

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13.

Counter and Compare Units

Figure 13-1 shows the Timer/Counter1 prescaler that supports two clocking modes, a synchronous clocking mode and an

asynchronous clocking mode. The synchronous clocking mode uses the system clock (CK) as the clock timebase and asynchronous mode uses the fast peripheral clock (PCK) as the clock time base. The PCKE bit from the PLLCSR register enables the asynchronous mode when it is set (‘1’).

Figure 13-1. Timer/Counter1 Prescaler

PCKE

PSR1

CK

PCK 64/32MHz

S

A

T1CK

14-bit T/C Prescaler

0

CS10

CS11

CS12

CS13

Timer/Counter 1 Count Enable

In the asynchronous clocking mode the clock selections are from PCK to PCK/16384 and stop, and in the synchronous

clocking mode the clock selections are from CK to CK/16384 and stop. The clock options are described in Table 13-2 on page 78

and the Timer/Counter1 control register, TCCR1. Setting the PSR1 bit in GTCCR register resets the prescaler. The

PCKE bit in the PLLCSR register enables the asynchronous mode. The frequency of the fast peripheral clock is 64MHz (or

32MHz in low speed mode).

13.1

Timer/Counter1

The Timer/Counter1 general operation is described in the asynchronous mode and the operation in the synchronous mode is mentioned only if there are differences between these two modes.

Figure 13-2 shows Timer/Counter 1 synchronization

register block diagram and synchronization delays in between registers. Note that all clock gating details are not shown in the figure. The Timer/Counter1 register values go through the internal synchronization registers, which cause the input synchronization delay, before affecting the counter operation. The registers TCCR1, GTCCR, OCR1A, OCR1B, and OCR1C can be read back right after writing the register. The read back values are delayed for the Timer/Counter1 (TCNT1) register and flags (OCF1A, OCF1B, and TOV1), because of the input and output synchronization.

The Timer/Counter1 features a high resolution and a high accuracy usage with the lower prescaling opportunities. It can also support two accurate, high speed, 8-bit pulse width modulators using clock speeds up to 64MHz (or 32MHz in low speed mode). In this mode, Timer/Counter1 and the output compare registers serve as dual stand-alone PWMs with

non-overlapping non-inverted and inverted outputs. Refer to Section 13.1.11 “Timer/Counter1 in PWM Mode” on page 82

for a detailed description on this function. Similarly, the high prescaling opportunities make this unit useful for lower speed functions or exact timing functions with infrequent actions.

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Figure 13-2. Timer/Counter 1 Synchronization Register Block Diagram

8-bit Data Bus

IO Registers

OCR1A

OCR1B

OCR1C

TCCR1

GTCCR

Input Synchronization

Registers

OCR1A_SI

OCR1B_SI

OCR1C_SI

TCCR1_SI

GTCCR_SI

Timer/Counter1 Output Synchronization

Registers

TCNT1

TCNT_SO

OCF1A_SO

TCNT1

OCF1A

TCNT1

OCF1A

OCF1B

TOV1

TCNT1_SI

OCF1A_SI

OCF1B_SI

TOV1_SI

OCF1B_SO

OCF1B

TOV1_SO

TOV1

PCKE

CK

S

A

S

PCK

SYNC

MODE

ASYNC

MODE

1/2 CK Delay

1-2 CK Delay

A

1 CK Delay

1 PCK Delay

1 CK Delay

~1 CK Delay

1/2 CK Delay

No Delay

Timer/Counter1 and the prescaler allow running the CPU from any clock source while the prescaler is operating on the fast

64MHz (or 32MHz in low speed mode) PCK clock in the asynchronous mode.

Note that the system clock frequency must be lower than one third of the PCK frequency. The synchronization mechanism of the asynchronous Timer/Counter1 needs at least two edges of the PCK when the system clock is high. If the frequency of the system clock is too high, it is a risk that data or control values are lost.

The following Figure 13-3 on page 76

shows the block diagram for Timer/Counter1.

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Figure 13-3. Timer/Counter1 Block Diagram

T/C1

Overflow

IRQ

T/C1

Compare

Match A IRQ

T/C1

Compare

Match B IRQ

OC1A

(PB1)

OC1A

(PB0)

Dead Time Generator

OC1B

(PB4)

OC1B

(PB3)

Dead Time Generator

Timer Int. Mask

Register (TIMSK)

Timer Int. Flag

Register (TIFR)

Timer/Counter1

Timer/Counter1

(TCNT1)

T/C Clear

T/C Control

Register 1 (TCCR1)

Global T/C Control

Register (GTCCR)

Timer/Counter1 Control Logic

CK

PCK

8-bit Comparator 8-bit Comparator 8-bit Comparator

T/C1 Output

Compare Register

(OCR1A)

T/C1 Output

Compare Register

(OCR1B)

T/C1 Output

Compare Register

(OCR1C)

76

8-bit Databus

Three status flags (overflow and compare matches) are found in the Timer/Counter interrupt flag register - TIFR. control signals are found in the Timer/Counter control registers TCCR1 and GTCCR. The interrupt enable/disable settings are found in the Timer/Counter interrupt mask register - TIMSK.

The Timer/Counter1 contains three output compare registers, OCR1A, OCR1B, and OCR1C as the data source to be compared with the Timer/Counter1 contents. In normal mode the output compare functions are operational with all three output compare registers. OCR1A determines action on the OC1A pin (PB1), and it can generate timer1 OC1A interrupt in normal mode and in PWM mode. Likewise, OCR1B determines action on the OC1B pin (PB3) and it can generate timer1

OC1B interrupt in normal mode and in PWM mode. OCR1C holds the Timer/Counter maximum value, i.e. the clear on compare match value. In the normal mode an overflow interrupt (TOV1) is generated when Timer/Counter1 counts from $FF to $00, while in the PWM mode the overflow interrupt is generated when Timer/Counter1 counts either from $FF to $00 or from OCR1C to $00. The inverted PWM outputs OC1A and OC1B are not connected in normal mode.

In PWM mode, OCR1A and OCR1B provide the data values against which the timer counter value is compared. Upon compare match the PWM outputs (OC1A, OC1A, OC1B, OC1B) are generated. In PWM mode, the timer counter counts up to the value specified in the output compare register OCR1C and starts again from $00. This feature allows limiting the counter “full” value to a specified value, lower than $FF. Together with the many prescaler options, flexible PWM frequency selection is provided.

Table 13-6 on page 84

lists clock selection and OCR1C values to obtain PWM frequencies from 20kHz to 250kHz in 10kHz steps and from 250kHz to 500kHz in 50kHz steps. Higher PWM frequencies can be obtained at the expense of resolution.

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13.1.1 Timer/Counter1 Control Register - TCCR1

Bit

$30 ($50)

Read/Write

Initial value

7

CTC1

R/W

0

6 5 4

PWM1A COM1A1 COM1A0

R/W R/W R/W

0 0 0

3

CS13

R/W

0

2

CS12

R/W

0

1

CS11

R/W

0

0

CS10

R/W

0

TCCR1

• Bit 7- CTC1: Clear Timer/Counter on Compare Match

When the CTC1 control bit is set (one), Timer/Counter1 is reset to $00 in the CPU clock cycle after a compare match with

OCR1C register value. If the control bit is cleared, Timer/Counter1 continues counting and is unaffected by a compare match.

• Bit 6- PWM1A: Pulse Width Modulator A Enable

When set (one) this bit enables PWM mode based on comparator OCR1A in Timer/Counter1 and the counter value is reset to $00 in the CPU clock cycle after a compare match with OCR1C register value.

• Bits 5,4 - COM1A1, COM1A0: Comparator A Output Mode, Bits 1 and 0

The COM1A1 and COM1A0 control bits determine any output pin action following a compare match with compare register A in Timer/Counter1. Output pin actions affect pin PB1 (OC1A). Since this is an alternative function to an I/O port, the corresponding direction control bit must be set (one) in order to control an output pin. Note that OC1A is not connected in normal mode.

Table 13-1. Comparator A Mode Select

COM1A1

0

0

1

1

COM1A0

0

1

0

1

Description

Timer/Counter comparator A disconnected from output pin OC1A.

Toggle the OC1A output line.

Clear the OC1A output line.

Set the OC1A output line

In PWM mode, these bits have different functions. Refer to

Table 13-4 on page 83 for a detailed description.

• Bits 3..0 - CS13, CS12, CS11, CS10: Clock Select Bits 3, 2, 1, and 0

The clock select bits 3, 2, 1, and 0 define the prescaling source of Timer/Counter1.

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Table 13-2. Timer/Counter1 Prescale Select

1

1

1

1

1

1

1

1

0

0

CS13

0

0

0

0

0

0

CS12

0

0

0

0

1

1

1

1

0

0

0

0

1

1

1

1

The Stop condition provides a timer enable/disable function.

0

0

1

1

1

1

0

0

1

1

CS11

0

0

0

0

1

1

0

1

0

1

0

1

0

1

0

1

CS10

0

1

0

1

0

1

Asynchronous

Clocking Mode

T/C1 stopped

PCK

PCK/2

PCK/4

PCK/8

PCK/16

PCK/32

PCK/64

PCK/128

PCK/256

PCK/512

PCK/1024

PCK/2048

PCK/4096

PCK/8192

PCK/16384

Synchronous

Clocking Mode

T/C1 stopped

CK

CK/2

CK/4

CK/8

CK/16

CK/32

CK/64

CK/128

CK/256

CK/512

CK/1024

CK/2048

CK/4096

CK/8192

CK/16384

13.1.2 General Timer/Counter1 Control Register - GTCCR

Bit

$2C ($4C)

Read/Write

Initial value

7

TSM

R/W

0

6 5 4 3 2

PWM1B COM1B1 COM1B0 FOC1B FOC1A

R/W R/W R/W W W

0 0 0 0 0

1

PSR1

R/W

0

0

PSR0

R/W

0

GTCCR

• Bit 6- PWM1B: Pulse Width Modulator B Enable

When set (one) this bit enables PWM mode based on comparator OCR1B in Timer/Counter1 and the counter value is reset to $00 in the CPU clock cycle after a compare match with OCR1C register value.

• Bits 5,4 - COM1B1, COM1B0: Comparator B Output Mode, Bits 1 and 0

The COM1B1 and COM1B0 control bits determine any output pin action following a compare match with compare register B in Timer/Counter1. Output pin actions affect pin PB3 (OC1B). Since this is an alternative function to an I/O port, the corresponding direction control bit must be set (one) in order to control an output pin. Note that OC1B is not connected in normal mode.

Table 13-3. Comparator B Mode Select

COM1B1

0

0

1

1

COM1B0

0

1

0

1

Description

Timer/Counter comparator B disconnected from output pin OC1B.

Toggle the OC1B output line.

Clear the OC1B output line.

Set the OC1B output line

In PWM mode, these bits have different functions. Refer to

Table 13-4 on page 83 for a detailed description.

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• Bit 3- FOC1B: Force Output Compare Match 1B

Writing a logical one to this bit forces a change in the compare match output pin PB3 (OC1B) according to the values already set in COM1B1 and COM1B0. If COM1B1 and COM1B0 written in the same cycle as FOC1B, the new settings will be used.

The force output compare bit can be used to change the output pin value regardless of the timer value. The automatic action programmed in COM1B1 and COM1B0 takes place as if a compare match had occurred, but no interrupt is generated. The

FOC1B bit always reads as zero. FOC1B is not in use if PWM1B bit is set.

• Bit 2- FOC1A: Force Output Compare Match 1A

Writing a logical one to this bit forces a change in the compare match output pin PB1 (OC1A) according to the values already set in COM1A1 and COM1A0. If COM1A1 and COM1A0 written in the same cycle as FOC1A, the new settings will be used.

The force output compare bit can be used to change the output pin value regardless of the timer value. The automatic action programmed in COM1A1 and COM1A0 takes place as if a compare match had occurred, but no interrupt is generated. The

FOC1A bit always reads as zero. FOC1A is not in use if PWM1A bit is set.

• Bit 1- PSR1: Prescaler Reset Timer/Counter1

When this bit is set (one), the Timer/Counter prescaler (TCNT1 is unaffected) will be reset. The bit will be cleared by hardware after the operation is performed. Writing a zero to this bit will have no effect. This bit will always read as zero.

13.1.3 Timer/Counter1 - TCNT1

Bit

$2F ($4F)

Read/Write

Initial value

7

MSB

R/W

0

6

R/W

0

5

R/W

0

4

R/W

0

3

R/W

0

2

R/W

0

1

R/W

0

0

LSB

R/W

0

TCNT1

This 8-bit register contains the value of Timer/Counter1.

Timer/Counter1 is realized as an up counter with read and write access. Due to synchronization of the CPU, Timer/Counter1 data written into Timer/Counter1 is delayed by one and half CPU clock cycles in synchronous mode and at most one CPU clock cycles for asynchronous mode.

13.1.4 Timer/Counter1 Output Compare RegisterA - OCR1A

Bit

$2E ($4E)

Read/Write

Initial value

7

MSB

R/W

0

6

R/W

0

5

R/W

0

4

R/W

0

3

R/W

0

2

R/W

0

1

R/W

0

0

LSB

R/W

0

OCR1A

The output compare register A is an 8-bit read/write register.

The Timer/Counter output compare register A contains data to be continuously compared with Timer/Counter1. Actions on compare matches are specified in TCCR1. A compare match does only occur if Timer/Counter1 counts to the OCR1A value.

A software write that sets TCNT1 and OCR1A to the same value does not generate a compare match.

A compare match will set the compare interrupt flag OCF1A after a synchronization delay following the compare event.

13.1.5 Timer/Counter1 Output Compare RegisterB - OCR1B

Bit

$2D ($4D)

Read/Write

Initial value

7

MSB

R/W

0

6

R/W

0

5

R/W

0

4

R/W

0

3

R/W

0

2

R/W

0

1

R/W

0

0

LSB

R/W

0

OCR1B

The output compare register B is an 8-bit read/write register.

The Timer/Counter output compare register B contains data to be continuously compared with Timer/Counter1. Actions on compare matches are specified in TCCR1. A compare match does only occur if Timer/Counter1 counts to the OCR1B value.

A software write that sets TCNT1 and OCR1B to the same value does not generate a compare match.

A compare match will set the compare interrupt flag OCF1B after a synchronization delay following the compare event.

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13.1.6 Timer/Counter1 Output Compare RegisterC - OCR1C

Bit

$2B ($4B)

Read/Write

Initial value

7

MSB

R/W

1

6

R/W

1

5

R/W

1

4

R/W

1

3

R/W

1

2

R/W

1

1

R/W

1

0

LSB

R/W

1

OCR1C

The output compare register C is an 8-bit read/write register.

The Timer/Counter output compare register C contains data to be continuously compared with Timer/Counter1. A compare match does only occur if Timer/Counter1 counts to the OCR1C value. A software write that sets TCNT1 and OCR1C to the same value does not generate a compare match. If the CTC1 bit in TCCR1 is set, a compare match will clear TCNT1.

This register has the same function in normal mode and PWM mode.

13.1.7 Timer/Counter Interrupt Mask Register - TIMSK

Bit

$39 ($59)

Read/Write

Initial value

R

0

7

-

6 5 4 3

OCIE1A OCIE1B OCIE0A OCIE0B

R/W

0

R/W

0

R/W

0

R/W

0

2

TOIE1

R/W

0

1

TOIE0

R/W

0

R

0

0

TIMSK

• Bit 7 - Res: Reserved Bit

This bit is a reserved bit in the Atmel

®

ATtiny25/45/85 and always reads as zero.

• Bit 6 - OCIE1A: Timer/Counter1 Output Compare Interrupt Enable

When the OCIE1A bit is set (one) and the I-bit in the status register is set (one), the Timer/Counter1 compare match A, interrupt is enabled. The corresponding interrupt at vector $003 is executed if a compare match A occurs. The compare flag in Timer/Counter1 is set (one) in the Timer/Counter interrupt flag register.

• Bit 5 - OCIE1B: Timer/Counter1 Output Compare Interrupt Enable

When the OCIE1B bit is set (one) and the I-bit in the status register is set (one), the Timer/Counter1 compare match B, interrupt is enabled. The corresponding interrupt at vector $009 is executed if a compare match B occurs. The compare flag in Timer/Counter1 is set (one) in the Timer/Counter interrupt flag register.

• Bit 4– OCIE0A: Timer/Counter Output Compare Match A Interrupt Enable

When the OCIE0A bit is written to one, and the I-bit in the status register is set, the Timer/Counter compare match A interrupt is enabled. The corresponding interrupt is executed if a compare match in Timer/Counter occurs, i.e., when the OCF0A bit is set in the Timer/Counter interrupt flag register – TIFR0.

• Bit 3 – OCIE0B: Timer/Counter Output Compare Match B Interrupt Enable

When the OCIE0B bit is written to one, and the I-bit in the status register is set, the Timer/Counter compare match B interrupt is enabled. The corresponding interrupt is executed if a compare match in Timer/Counter occurs, i.e., when the OCF0B bit is set in the Timer/Counter interrupt flag register – TIFR0.

• Bit 2 - TOIE1: Timer/Counter1 Overflow Interrupt Enable

When the TOIE1 bit is set (one) and the I-bit in the status register is set (one), the Timer/Counter1 overflow interrupt is enabled. The corresponding interrupt (at vector $004) is executed if an overflow in Timer/Counter1 occurs. The overflow flag

(timer1) is set (one) in the Timer/Counter interrupt flag register - TIFR.

• Bit 0 - Res: Reserved Bit

This bit is a reserved bit in the Atmel ATtiny25/45/85 and always reads as zero.

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13.1.8 Timer/Counter Interrupt Flag Register - TIFR

Bit

$38 ($58)

Read/Write

Initial value

7

-

R

0

6

OCF1A

R/W

0

5

OCF1B

R/W

0

4

OCF0A

R

0

3

OCF0B

R

0

2

TOV1

R/W

0

1

TOV0

R/W

0

0

-

R

0

TIFR

• Bit 7 - Res: Reserved Bit

This bit is a reserved bit in the Atmel

®

ATtiny25/45/85 and always reads as zero.

• Bit 6 - OCF1A: Output Compare Flag 1A

The OCF1A bit is set (one) when compare match occurs between Timer/Counter1 and the data value in OCR1A - output compare register 1A. OCF1A is cleared by hardware when executing the corresponding interrupt handling vector.

Alternatively, OCF1A is cleared, after synchronization clock cycle, by writing a logic one to the flag. When the I-bit in SREG,

OCIE1A, and OCF1A are set (one), the Timer/Counter1 A compare match interrupt is executed.

• Bit 5 - OCF1B: Output Compare Flag 1B

The OCF1B bit is set (one) when compare match occurs between Timer/Counter1 and the data value in OCR1B - output compare register 1A. OCF1B is cleared by hardware when executing the corresponding interrupt handling vector.

Alternatively, OCF1B is cleared, after synchronization clock cycle, by writing a logic one to the flag. When the I-bit in SREG,

OCIE1B, and OCF1B are set (one), the Timer/Counter1 B compare match interrupt is executed.

• Bit 2 - TOV1: Timer/Counter1 Overflow Flag

In normal mode (PWM1A=0 and PWM1B=0) the bit TOV1 is set (one) when an overflow occurs in Timer/Counter1. The bit

TOV1 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, TOV1 is cleared, after synchronization clock cycle, by writing a logical one to the flag.

In PWM mode (either PWM1A=1 or PWM1B=1) the bit TOV1 is set (one) when compare match occurs between

Timer/Counter1 and data value in OCR1C - output compare register 1C. Clearing the Timer/Counter1 with the bit CTC1 does not generate an overflow.

When the SREG I-bit, and TOIE1 (Timer/Counter1 overflow interrupt enable), and TOV1 are set (one), the Timer/Counter1 overflow interrupt is executed.

• Bit 0 - Res: Reserved Bit

This bit is a reserved bit in the Atmel ATtiny25/45/85 and always reads as zero.

13.1.9 PLL Control and Status Register - PLLCSR

Bit

$27 ($27)

Read/Write

Initial value

7

LSM

R/W

0

6

-

R

0

5

-

R

0

4

-

R

0

3

-

R

0

2

PCKE

R/W

0

1

PLLE

R/W

0/1

0

PLOCK

R

0

PLLCSR

• Bit 7- LSM: Low Speed Mode

The high speed mode is enabled as default and the fast peripheral clock is 64MHz, but the low speed mode can be set by writing the LSM bit to one. Then the fast peripheral clock is scaled down to 32MHz. The low speed mode must be set, if the supply voltage is below 2.7 volts, because the Timer/Counter1 is not running fast enough on low voltage levels. It is highly recommended that Timer/Counter1 is stopped whenever the LSM bit is changed.

• Bit 6.. 3- Res: Reserved Bits

These bits are reserved bits in the Atmel ATtiny25/45/85 and always read as zero.

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• Bit 2- PCKE: PCK Enable

The PCKE bit change the Timer/Counter1 clock source. When it is set, the asynchronous clock mode is enabled and fast

64MHz (or 32MHz in low speed mode) PCK clock is used as Timer/Counter1 clock source. If this bit is cleared, the synchronous clock mode is enabled, and system clock CK is used as Timer/Counter1 clock source. This bit can be set only if PLLE bit is set. It is safe to set this bit only when the PLL is locked i.e the PLOCK bit is 1. The bit PCKE can only be set, if the PLL has been enabled earlier.

• Bit 1- PLLE: PLL Enable

When the PLLE is set, the PLL is started and if needed internal RC-oscillator is started as a PLL reference clock. If PLL is selected as a system clock source the value for this bit is always 1.

• Bit 0- PLOCK: PLL Lock Detector

When the PLOCK bit is set, the PLL is locked to the reference clock, and it is safe to enable PCK for Timer/Counter1. After the PLL is enabled, it takes about 100 micro seconds for the PLL to lock.

13.1.10 Timer/Counter1 Initialization for Asynchronous Mode

To change Timer/Counter1 to the asynchronous mode, first enable PLL, wait 100µs before polling the PLOCK bit until it is set, and then set the PCKE bit.

13.1.11 Timer/Counter1 in PWM Mode

When the PWM mode is selected, Timer/Counter1 and the output compare register C - OCR1C form a dual 8-bit, freerunning and glitch-free PWM generator with outputs on the PB1(OC1A) and PB3(OC1B) pins and inverted outputs on pins

PB0(OC1A) and PB2(OC1B). As default non-overlapping times for complementary output pairs are zero, but they can be

inserted using a dead time generator (see Section 14. “Dead Time Generator” on page 85

).

Figure 13-4. The PWM Output Pair

PWM1x

PWM1x t non-overlap

= 0 t non-overlap

= 0 x = A or B

When the counter value match the contents of OCR1A or OCR1B, the OC1A and OC1B outputs are set or cleared according to the COM1A1/COM1A0 or COM1B1/COM1B0 bits in the Timer/Counter1 control register A - TCCR1, as shown in

Table 13-4 on page 83 .

Timer/Counter1 acts as an up-counter, counting from $00 up to the value specified in the output compare register OCR1C, and starting from $00 up again. A compare match with OC1C will set an overflow interrupt flag (TOV1) after a synchronization delay following the compare event.

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Table 13-4. Compare Mode Select in PWM Mode

COM11

0

0

1

1

COM10

0

1

0

1

Effect on Output Compare Pins

OC1x not connected.

OC1x not connected.

OC1x cleared on compare match. Set whenTCNT1 = $01.

OC1x set on compare match. Cleared when TCNT1 = $00.

OC1x cleared on compare match. Set when TCNT1 = $01.

OC1x not connected.

OC1x Set on compare match. Cleared when TCNT1= $01.

OC1x not connected.

Note that in PWM mode, writing to the output compare registers OCR1A or OCR1B, the data value is first transferred to a temporary location. The value is latched into OCR1A or OCR1B when the Timer/Counter reaches OCR1C. This prevents the occurrence of odd-length PWM pulses (glitches) in the event of an unsynchronized OCR1A or OCR1B. See

Figure 13-5 for

an example.

Figure 13-5. Effects of Unsynchronized OCR Latching

Compare Value changes

Counter Value

Compare Value

PMW Output OC1x

Synchronized OC1x Latch

Compare Value changes

Counter Value

Compare Value

PMW Output OC1x

Glitch Unsynchronized OC1x Latch

During the time between the write and the latch operation, a read from OCR1A or OCR1B will read the contents of the temporary location. This means that the most recently written value always will read out of OCR1A or OCR1B.

When OCR1A or OCR1B contain $00 or the top value, as specified in OCR1C register, the output PB1(OC1A) or

PB3(OC1B) is held low or high according to the settings of COM1A1/COM1A0. This is shown in Table 13-5 on page 83

.

Table 13-5. PWM Outputs OCR1x = $00 or OCR1C, x = A or B

COM1x1

0

0

1

1

1

1

COM1x0

1

1

0

0

1

1

OCR1x

$00

OCR1C

$00

OCR1C

$00

OCR1C

Output OC1x

L

H

L

H

H

L

Output OC1x

H

L

Not connected.

Not connected.

Not connected.

Not connected.

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In PWM mode, the timer overflow flag - TOV1 is set when the TCNT1 counts to the OCR1C value and the TCNT1 is reset to

$00. The timer overflow interrupt1 is executed when TOV1 is set provided that timer overflow interrupt and global interrupts are enabled. This also applies to the timer output compare flags and interrupts.

The frequency of the PWM will be timer clock 1 frequency divided by (OCR1C value + 1). See the following equation:

f

PWM

=

(

f

OCR1C + 1

)

Resolution shows how many bit is required to express the value in the OCR1C register. It is calculated by following equation

Resolution

PWM

= log

2

(OCR1C + 1).

Table 13-6. Timer/Counter1 Clock Prescale Select in the Asynchronous Mode

PWM Frequency

20kHz

30kHz

40kHz

50kHz

60kHz

70kHz

80kHz

90kHz

100kHz

110kHz

120kHz

130kHz

140kHz

150kHz

160kHz

170kHz

180kHz

190kHz

200kHz

250kHz

300kHz

350kHz

400kHz

450kHz

500kHz

Clock Selection

PCK/16

PCK/16

PCK/8

PCK/8

PCK/8

PCK/4

PCK/4

PCK/4

PCK/4

PCK/4

PCK/4

PCK/2

PCK/2

PCK/2

PCK/2

PCK/2

PCK/2

PCK/2

PCK/2

PCK

PCK

PCK

PCK

PCK

PCK

CS13..CS10

0101

0101

0100

0100

0100

0011

0011

0011

0011

0011

0011

0010

0010

0010

0010

0010

0010

0010

0010

0001

0001

0001

0001

0001

0001

245

228

212

199

177

159

144

132

OCR1C

199

132

199

159

132

228

199

255

212

182

159

187

177

167

159

141

127

RESOLUTION

7.6

7.1

7.6

7.3

7.1

7.8

7.6

7.9

7.8

7.7

7.6

7.5

7.3

7.2

7.1

8.0

7.7

7.5

7.3

7.6

7.5

7.4

7.3

7.1

7.0

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14.

Dead Time Generator

The dead time generator is provided for the Timer/Counter1 PWM output pairs to allow driving external power control switches safely. The dead time generator is a separate block that can be connected to Timer/Counter1 and it is used to insert dead times (non-overlapping times) for the Timer/Counter1 complementary output pairs (OC1A-OC1A and

OC1B-OC1B). The sharing of tasks is as follows: the Timer/Counter generates the PWM output and the dead time generator generates the non-overlapping PWM output pair from the Timer/Counter PWM signal. Two dead time generators are provided, one for each PWM output. The non-overlap time is adjustable and the PWM output and it’s complementary output are adjusted separately, and independently for both PWM outputs.

Figure 14-1. Timer/Counter1 and Dead Time Generators

PCKE

T15M

CK

Timer/Counter1

PWM Generator

PWM1A PWM1B

PCK

DT1AH

DT1AL

Dead Time Generator Dead Time Generator

DT1BH

DT1BL

OC1A OC1A OC1B OC1B

The dead time generation is based on the 4-bit down counters that count the dead time, as shown in

Figure 14-1

There is a dedicated prescaler in front of the dead time generator that can divide the Timer/Counter1 clock (PCK or CK) by 1, 2, 4 or 8.

This provides for large range of dead times that can be generated. The prescaler is controlled by two control bits

DTPS11..10 from the I/O register at address 0x23. The block has also a rising and falling edge detector that is used to start the dead time counting period. Depending on the edge, one of the transitions on the rising edges, OC1x or OC1x is delayed until the counter has counted to zero. The comparator is used to compare the counter with zero and stop the dead time insertion when zero has been reached. The counter is loaded with a 4-bit DT1xH or DT1xL value from DT1x I/O register, depending on the edge of the PWM generator output when the dead time insertion is started.

Figure 14-2. Dead Time Generator

T/C1 Clock DTPS11..10

Comparator

OC1x

Dead Time

Prescaler

Clock Control 4-bit Counter

OC1x

DT1x

I/O Register

PWM1x

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The length of the counting period is user adjustable by selecting the dead time prescaler setting in 0x23 register, and selecting then the dead time value in I/O register DT1x. The DT1x register consists of two 4-bit fields, DT1xH and DT1xL that control the dead time periods of the PWM output and its’ complementary output separately. Thus the rising edge of OC1x and OC1x can have different dead time periods. The dead time is adjusted as the number of prescaled dead time generator clock cycles.

Figure 14-3. The Complementary Output Pair

PWM1x

OC1x

OC1x x= A or B t non-overlap/rising edge t non-overlap/falling edge

14.1

Timer/Counter1 Dead Time Prescaler register 1 - DTPS1

Bit

$23 ($43)

Read/Write

Initial value

7

R

0

6

R

0

5

R

0

4

R

0

3

R

0

2

R

0

1 0

DTPS11 DTPS10

R/W R/W

0 0

DTPS1

The dead time prescaler register, DTPS1 is a 2-bit read/write register.

Bits 1 - 0 - DTPS1: Timer/Counter1 dead time prescaler register 1

The dedicated dead time prescaler in front of the dead time generator can divide the Timer/Counter1 clock (PCK or CK) by

1, 2, 4 or 8 providing a large range of dead times that can be generated. The dead time prescaler is controlled by two bits

DTPS11..10 from the dead time prescaler register. These bits define the division factor of the dead time prescaler. The

division factors are given in Table 14-1

.

Table 14-1. Division Factors of the Dead Time Prescaler

DTPS11

0

0

1

1

DTPS10

0

1

0

1

Prescaler divides the T/C1 clock by

1x (no division)

2x

4x

8x

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14.2

Timer/Counter1 Dead Time A - DT1A

Bit

$25 ($45)

Read/Write

Initial value

7 6 5 4 3 2 1 0

DT1AH3 DT1AH2 DT1AH1 DT1AH0 DT1AL3 DT1AL2 DT1AL1 DT1AL0

R/W R/W R/W R/W R/W R/W R/W R/W

0 0 0 0 0 0 0 0

DT1A

The dead time value register A is an 8-bit read/write register.

The dead time delay of is adjusted by the dead time value register, DT1A. The register consists of two fields, DT1AH3..0 and

DT1AL3..0, one for each complementary output. Therefore a different dead time delay can be adjusted for the rising edge of

OC1A and the rising edge of OC1A.

• Bits 7..4- DT1AH3..DT1AH0: Dead Time Value for OC1A Output

The dead time value for the OC1A output. The dead time delay is set as a number of the prescaled Timer/Counter clocks.

The minimum dead time is zero and the maximum dead time is the prescaled time/counter clock period multiplied by 15.

• Bits 3..0- DT1AL3..DT1AL0: Dead Time Value for OC1A Output

The dead time value for the OC1A output. The dead time delay is set as a number of the prescaled Timer/Counter clocks.

The minimum dead time is zero and the maximum dead time is the prescaled time/counter clock period multiplied by 15.

14.3

Timer/Counter1 Dead Time B - DT1B

Bit

$25 ($45)

Read/Write

Initial value

7 6 5 4 3 2 1 0

DT1BH3 DT1BH2 DT1BH1 DT1BH0 DT1BL3 DT1BL2 DT1BL1 DT1BL0

R/W R/W R/W R/W R/W R/W R/W R/W

0 0 0 0 0 0 0 0

DT1B

The dead time value register bit an 8-bit read/write register.

The dead time delay of is adjusted by the dead time value register, DT1B. The register consists of two fields, DT1BH3..0 and

DT1BL3..0, one for each complementary output. Therefore a different dead time delay can be adjusted for the rising edge of

OC1A and the rising edge of OC1A.

• Bits 7..4- DT1BH3..DT1BH0: Dead Time Value for OC1B Output

The dead time value for the OC1B output. The dead time delay is set as a number of the prescaled Timer/Counter clocks.

The minimum dead time is zero and the maximum dead time is the prescaled time/counter clock period multiplied by 15.

• Bits 3..0- DT1BL3..DT1BL0: Dead Time Value for OC1B Output

The dead time value for the OC1B output. The dead time delay is set as a number of the prescaled Timer/Counter clocks.

The minimum dead time is zero and the maximum dead time is the prescaled time/counter clock period multiplied by 15.

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15.

Universal Serial Interface – USI

The universal serial interface, or USI, provides the basic hardware resources needed for serial communication. Combined with a minimum of control software, the USI allows significantly higher transfer rates and uses less code space than solutions based on software only. Interrupts are included to minimize the processor load. The main features of the USI are:

Two-wire synchronous data transfer (master or slave, f

SCLmax

= f

CK

/16)

Three-wire synchronous data transfer (master or slave f

SCKmax

= f

CK

/4)

Data received interrupt

Wakeup from idle mode

In two-wire mode: Wake-up from all sleep modes, including power-down mode

Two-wire start condition detector with interrupt capability

15.1

Overview

A simplified block diagram of the USI is shown on

Figure 15-1 For the actual placement of I/O pins, refer to

Figure 1 on page 2 . CPU accessible I/O registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O

register and bit locations are listed in the

Section 15.4 “USI Register Descriptions” on page 94

.

Figure 15-1. Universal Serial Interface, Block Diagram

DO (Output only)

D

LE

Q

DI/SDA (Input/ Open Drain))

USIDR

3

2

1

0

TIM0 COMP

USIDB

4-bit Counter

USISR

2

3

2

1

0

[1]

0

1

Clock

Hold

Two-wire Clock

Control Unit

USCK/SCL (Input/ Open Drain))

USICR

The 8-bit shift register is directly accessible via the data bus and contains the incoming and outgoing data. The register has no buffering so the data must be read as quickly as possible to ensure that no data is lost. The most significant bit is connected to one of two output pins depending of the wire mode configuration. A transparent latch is inserted between the serial register output and output pin, which delays the change of data output to the opposite clock edge of the data input sampling. The serial input is always sampled from the data input (DI) pin independent of the configuration.

The 4-bit counter can be both read and written via the data bus, and can generate an overflow interrupt. Both the serial register and the counter are clocked simultaneously by the same clock source.

This allows the counter to count the number of bits received or transmitted and generate an interrupt when the transfer is complete. Note that when an external clock source is selected the counter counts both clock edges. In this case the counter counts the number of edges, and not the number of bits. The clock can be selected from three different sources: The USCK pin, Timer/Counter0 compare match or from software.

The two-wire clock control unit can generate an interrupt when a start condition is detected on the two-wire bus. It can also generate wait states by holding the clock pin low after a start condition is detected, or after the counter overflows.

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15.2

Functional Descriptions

15.2.1 Three-wire Mode

The USI three-wire mode is compliant to the serial peripheral interface (SPI) mode 0 and 1, but does not have the slave select (SS) pin functionality. However, this feature can be implemented in software if necessary. Pin names used by this mode are: DI, DO, and USCK.

Figure 15-2. Three-wire Mode Operation, Simplified Diagram

DO

Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0

DI

USCK

SLAVE

DO

Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0

DI

USCK

PORTxn

MASTER

Figure 15-2 shows two USI units operating in three-wire mode, one as master and one as slave. The two shift registers are

interconnected in such way that after eight USCK clocks, the data in each register are interchanged. The same clock also increments the USI’s 4-bit counter. The counter overflow (interrupt) flag, or USIOIF, can therefore be used to determine when a transfer is completed. The clock is generated by the master device software by toggling the USCK pin via the PORT register or by writing a one to the USITC bit in USICR.

Figure 15-3. Three-wire Mode, Timing Diagram

CYCLE

(Reference) 1 2 3 4 5 6 7 8

USCK

USCK

DO

MSB 6 5 4 3 2 1 LSB

DI

MSB 6 5 4 3 2 1 LSB

A B C D E

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The three-wire mode timing is shown in Figure 15-3 on page 89

At the top of the figure is a USCK cycle reference. One bit is shifted into the USI shift register (USIDR) for each of these cycles. The USCK timing is shown for both external clock modes.

In external clock mode 0 (USICS0 = 0), DI is sampled at positive edges, and DO is changed (data register is shifted by one) at negative edges. External clock mode 1 (USICS0 = 1) uses the opposite edges versus mode 0, i.e., samples data at negative and changes the output at positive edges. The USI clock modes corresponds to the SPI data mode 0 and 1.

Referring to the timing diagram ( Figure 15-3 on page 89

), a bus transfer involves the following steps:

1.

The slave device and master device sets up its data output and, depending on the protocol used, enables its output driver (mark A and B). The output is set up by writing the data to be transmitted to the serial data register.

Enabling of the output is done by setting the corresponding bit in the port data direction register. Note that point A and B does not have any specific order, but both must be at least one half USCK cycle before point C where the data is sampled. This must be done to ensure that the data setup requirement is satisfied. The 4-bit counter is reset to zero.

2.

The master generates a clock pulse by software toggling the USCK line twice (C and D). The bit value on the slave and master’s data input (DI) pin is sampled by the USI on the first edge (C), and the data output is changed on the opposite edge (D). The 4-bit counter will count both edges.

3.

Step 2. is repeated eight times for a complete register (byte) transfer.

4.

After eight clock pulses (i.e., 16 clock edges) the counter will overflow and indicate that the transfer is completed.

The data bytes transferred must now be processed before a new transfer can be initiated. The overflow interrupt will wake up the processor if it is set to Idle mode. Depending of the protocol used the slave device can now set its output to high impedance.

15.2.2 SPI Master Operation Example

The following code demonstrates how to use the USI module as a SPI master:

SPITransfer: sts ldi

USIDR,r16 r16,(1<<USIOIF) sts ldi

USISR,r16 r16,(1<<USIWM0)|(1<<USICS1)|(1<<USICLK)|(1<<USITC)

SPITransfer_loop: sts USICR,r16 lds r16, USISR sbrs r16, USIOIF rjmp SPITransfer_loop lds r16,USIDR ret

The code is size optimized using only eight instructions (+ ret). The code example assumes that the DO and USCK pins are enabled as output in the DDRE register. The value stored in register r16 prior to the function is called is transferred to the slave device, and when the transfer is completed the data received from the slave is stored back into the r16 register.

The second and third instructions clears the USI counter overflow flag and the USI counter value. The fourth and fifth instruction set three-wire mode, positive edge shift register clock, count at USITC strobe, and toggle USCK. The loop is repeated 16 times.

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The following code demonstrates how to use the USI module as a SPI master with maximum speed (fsck = fck/4):

SPITransfer_Fast: sts USIDR,r16 ldi r16,(1<<USIWM0)|(0<<USICS0)|(1<<USITC) ldi r17,(1<<USIWM0)|(0<<USICS0)|(1<<USITC)|(1<<USICLK) ret sts USICR,r17 sts USICR,r16 sts USICR,r17 sts USICR,r16 sts USICR,r17 sts USICR,r16 sts USICR,r17 sts USICR,r16 sts USICR,r17 sts USICR,r16 sts USICR,r17 sts USICR,r16 sts USICR,r17 sts USICR,r17 lds r16,USIDR

15.2.3 SPI Slave Operation Example

The following code demonstrates how to use the USI module as a SPI slave: init: ldi sts r16,(1<<USIWM0)|(1<<USICS1)

USICR,r16

...

SlaveSPITransfer: sts USIDR,r16 ldi r16,(1<<USIOIF) sts USISR,r16

SlaveSPITransfer_loop: lds r16, USISR sbrs r16, USIOIF rjmp SlaveSPITransfer_loop lds ret r16,USIDR

The code is size optimized using only eight instructions (+ ret). The code example assumes that the DO is configured as output and USCK pin is configured as input in the DDR register. The value stored in register r16 prior to the function is called is transferred to the master device, and when the transfer is completed the data received from the master is stored back into the r16 register.

Note that the first two instructions is for initialization only and needs only to be executed once.These instructions sets three-wire mode and positive edge shift register clock. The loop is repeated until the USI counter overflow flag is set.

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15.2.4 Two-wire Mode

The USI two-wire mode is compliant to the inter IC (TWI) bus protocol, but without slew rate limiting on outputs and input noise filtering. Pin names used by this mode are SCL and SDA.

Figure 15-4. Two-wire Mode Operation, Simplified Diagram

VCC

Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0

SDA

Two-wire

Clock

Control Unit

Hold

SCL

SCL

SLAVE

SDA

Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0

SCL

PORTxn

MASTER

Figure 15-4 shows two USI units operating in two-wire mode, one as master and one as slave. It is only the physical layer

that is shown since the system operation is highly dependent of the communication scheme used. The main differences between the master and slave operation at this level, is the serial clock generation which is always done by the master, and only the slave uses the clock control unit. Clock generation must be implemented in software, but the shift operation is done automatically by both devices. Note that only clocking on negative edge for shifting data is of practical use in this mode. The slave can insert wait states at start or end of transfer by forcing the SCL clock low. This means that the master must always check if the SCL line was actually released after it has generated a positive edge.

Since the clock also increments the counter, a counter overflow can be used to indicate that the transfer is completed. The clock is generated by the master by toggling the USCK pin via the PORT register.

The data direction is not given by the physical layer. A protocol, like the one used by the TWI-bus, must be implemented to control the data flow.

Figure 15-5. Two-wire Mode, Typical Timing Diagram

SDA

SCL

S

1 to 7

ADDRESS

8

R/W

9

ACK

1 to 8

DATA

9

ACK

1 to 8

DATA

9

ACK

P

A B C D E F

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Referring to the timing diagram ( Figure 15-5 on page 92

), a bus transfer involves the following steps:

1.

The a start condition is generated by the master by forcing the SDA low line while the SCL line is high (A). SDA can be forced low either by writing a zero to bit 7 of the shift register, or by setting the corresponding bit in the

PORT register to zero. Note that the data direction register bit must be set to one for the output to be enabled. The slave device’s start detector logic (

Figure 15-5

) detects the start condition and sets the USISIF flag. The flag can generate an interrupt if necessary.

2.

In addition, the start detector will hold the SCL line low after the master has forced an negative edge on this line

(B). This allows the Slave to wake up from sleep or complete its other tasks before setting up the shift register to receive the address. This is done by clearing the start condition flag and reset the counter.

3.

The master set the first bit to be transferred and releases the SCL line (C). The slave samples the data and shift it into the serial register at the positive edge of the SCL clock.

4.

After eight bits are transferred containing slave address and data direction (read or write), the slave counter overflows and the SCL line is forced low (D). If the slave is not the one the master has addressed, it releases the

SCL line and waits for a new start condition.

5.

If the slave is addressed it holds the SDA line low during the acknowledgment cycle before holding the SCL line low again (i.e., the counter register must be set to 14 before releasing SCL at (D)). Depending of the R/W bit the master or slave enables its output. If the bit is set, a master read operation is in progress (i.e., the slave drives the

SDA line) The slave can hold the SCL line low after the acknowledge (E).

6.

Multiple bytes can now be transmitted, all in same direction, until a stop condition is given by the master (F). Or a new start condition is given.

If the slave is not able to receive more data it does not acknowledge the data byte it has last received. When the master does a read operation it must terminate the operation by force the acknowledge bit low after the last byte transmitted.

Figure 15-6. Start Condition Detector, Logic Diagram

USISIF

CLOCK

HOLD

SDA

D Q

CLR

D Q

CLR

SCL

Write (USISIF)

15.2.5 Start Condition Detector

The start condition detector is shown in Figure 15-6

The SDA line is delayed (in the range of 50 to 300 ns) to ensure valid sampling of the SCL line. The start condition detector is only enabled in two-wire mode.

The start condition detector is working asynchronously and can therefore wake up the processor from the power-down sleep mode. However, the protocol used might have restrictions on the SCL hold time. Therefore, when using this feature in this case the oscillator start-up time set by the CKSEL fuses (see

Section 5.1 “Clock Systems and their Distribution” on page 19 )

must also be taken into the consideration. Refer to the USISIF bit description on page 95

for further details.

15.3

Alternative USI Usage

When the USI unit is not used for serial communication, it can be set up to do alternative tasks due to its flexible design.

15.3.1 Half-duplex Asynchronous Data Transfer

By utilizing the shift register in three-wire mode, it is possible to implement a more compact and higher performance UART than by software only.

15.3.2 4-bit Counter

The 4-bit counter can be used as a stand-alone counter with overflow interrupt. Note that if the counter is clocked externally, both clock edges will generate an increment.

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15.3.3 12-bit Timer/Counter

Combining the USI 4-bit counter and Timer/Counter0 allows them to be used as a 12-bit counter.

15.3.4 Edge Triggered External Interrupt

By setting the counter to maximum value (F) it can function as an additional external interrupt. The overflow flag and interrupt

Enable bit are then used for the external interrupt. This feature is selected by the USICS1 bit.

15.3.5 Software Interrupt

The counter overflow interrupt can be used as a software interrupt triggered by a clock strobe.

15.4

USI Register Descriptions

15.4.1 USI Data Register – USIDR

Bit

Read/Write

Initial Value

7

MSB

R/W

0

6

R/W

0

5

R/W

0

4

R/W

0

3

R/W

0

2

R/W

0

1

R/W

0

0

LSB

R/W

0

USIDR

When accessing the USI data register (USIDR) the serial register can be accessed directly. If a serial clock occurs at the same cycle the register is written, the register will contain the value written and no shift is performed. A (left) shift operation is performed depending of the USICS1..0 bits setting. The shift operation can be controlled by an external clock edge, by a

Timer/Counter0 compare match, or directly by software using the USICLK strobe bit. Note that even when no wire mode is selected (USIWM1..0 = 0) both the external data input (DI/SDA) and the external clock input (USCK/SCL) can still be used by the shift register.

The output pin in use, DO or SDA depending on the wire mode, is connected via the output latch to the most significant bit

(bit 7) of the data register. The output latch is open (transparent) during the first half of a serial clock cycle when an external clock source is selected (USICS1 = 1), and constantly open when an internal clock source is used (USICS1 = 0). The output will be changed immediately when a new MSB written as long as the latch is open. The latch ensures that data input is sampled and data output is changed on opposite clock edges.

Note that the corresponding data direction register to the pin must be set to one for enabling data output from the shift register.

15.4.2 USI Buffer Register – USIBR

Bit

Read/Write

Initial Value

7

MSB

R

0

6

R

0

5

R

0

4

R

0

3

R

0

2

R

0

1

R

0

0

LSB

R

0

USIBR

The content of the serial register is loaded to the USI buffer register when the trasfer is completed, and instead of accessing the USI data register (the serial register) the USI data buffer can be accessed when the CPU reads the received data. This gives the CPU time to handle other program tasks too as the controlling of the USI is not so timing critical. The USI flags as set same as when reading the USIDR register.

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15.4.3 USI Status Register – USISR

Bit

Read/Write

Initial Value

7 6

USISIF USIOIF

R/W R/W

0 0

5

USIPF

R/W

0

4

USIDC

R

0

3 2 1 0

USICNT3 USICNT2 USICNT1 USICNT0 USISR

R/W R/W R/W R/W

0 0 0 0

The status register contains interrupt flags, line status flags and the counter value.

• Bit 7 – USISIF: Start Condition Interrupt Flag

When two-wire mode is selected, the USISIF flag is set (to one) when a start condition is detected. When output disable mode or three-wire mode is selected and (USICSx = 0b11 and USICLK = 0) or (USICS = 0b10 and USICLK = 0), any edge on the SCK pin sets the flag.

An interrupt will be generated when the flag is set while the USISIE bit in USICR and the global interrupt enable flag are set.

The flag will only be cleared by writing a logical one to the USISIF bit. Clearing this bit will release the start detection hold of

USCL in two-wire mode.

A start condition interrupt will wakeup the processor from all sleep modes.

• Bit 6 – USIOIF: Counter Overflow Interrupt Flag

This flag is set (one) when the 4-bit counter overflows (i.e., at the transition from 15 to 0). An interrupt will be generated when the flag is set while the USIOIE bit in USICR and the global interrupt enable flag are set. The flag will only be cleared if a one is written to the USIOIF bit. Clearing this bit will release the counter overflow hold of SCL in two-wire mode.

A counter overflow interrupt will wakeup the processor from Idle sleep mode.

• Bit 5 – USIPF: Stop Condition Flag

When two-wire mode is selected, the USIPF Flag is set (one) when a stop condition is detected. The flag is cleared by writing a one to this bit. Note that this is not an interrupt flag. This signal is useful when implementing two-wire bus master arbitration.

• Bit 4 – USIDC: Data Output Collision

This bit is logical one when bit 7 in the shift register differs from the physical pin value. The flag is only valid when two-wire mode is used. This signal is useful when implementing two-wire bus master arbitration.

• Bits 3..0 – USICNT3..0: Counter Value

These bits reflect the current 4-bit counter value. The 4-bit counter value can directly be read or written by the CPU.

The 4-bit counter increments by one for each clock generated either by the external clock edge detector, by a

Timer/Counter0 compare match, or by software using USICLK or USITC strobe bits. The clock source depends of the setting of the USICS1..0 bits. For external clock operation a special feature is added that allows the clock to be generated by writing to the USITC strobe bit. This feature is enabled by write a one to the USICLK bit while setting an external clock source

(USICS1 = 1).

Note that even when no wire mode is selected (USIWM1..0 = 0) the external clock input (USCK/SCL) are can still be used by the counter.

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15.4.4 USI Control Register – USICR

Bit

Read/Write

Initial Value

7

USISIE

R/W

0

6

USIOIE

R/W

0

5 4 3 2 1 0

USIWM1 USIWM0 USICS1 USICS0 USICLK USITC USICR

R/W R/W R/W R/W W W

0 0 0 0 0 0

The control register includes interrupt enable control, wire mode setting, clock select setting, and clock strobe.

• Bit 7 – USISIE: Start Condition Interrupt Enable

Setting this bit to one enables the start condition detector interrupt. If there is a pending interrupt when the USISIE and the

global interrupt enable flag is set to one, this will immediately be executed. Refer to the USISIF bit description on page 95

for further details.

• Bit 6 – USIOIE: Counter Overflow Interrupt Enable

Setting this bit to one enables the counter overflow interrupt. If there is a pending interrupt when the USIOIE and the global

interrupt enable flag is set to one, this will immediately be executed. Refer to the USIOIF bit description on page 95

for further details.

• Bit 5..4 – USIWM1..0: Wire Mode

These bits set the type of wire mode to be used. Basically only the function of the outputs are affected by these bits. Data and clock inputs are not affected by the mode selected and will always have the same function. The counter and shift register can therefore be clocked externally, and data input sampled, even when outputs are disabled. The relations

between USIWM1..0 and the USI operation is summarized in Table 15-1 on page 96

.

Table 15-1. Relations between USIWM1..0 and the USI Operation

USIWM1

0

USIWM0 Description

0 Outputs, clock hold, and start detector disabled. Port pins operates as normal.

0

1

1

0

Three-wire mode. Uses DO, DI, and USCK pins.

The Data Output (DO) pin overrides the corresponding bit in the PORT Register in this mode.

However, the corresponding DDR bit still controls the data direction. When the port pin is set as input the pins pull-up is controlled by the PORT bit.

The Data Input (DI) and Serial Clock (USCK) pins do not affect the normal port operation.

When operating as master, clock pulses are software generated by toggling the PORT

Register, while the data direction is set to output. The USITC bit in the USICR Register can be used for this purpose.

Two-wire mode. Uses SDA (DI) and SCL (USCK) pins

(1)

.

The Serial Data (SDA) and the Serial Clock (SCL) pins are bi-directional and uses opencollector output drives. The output drivers are enabled by setting the corresponding bit for

SDA and SCL in the DDR Register.

When the output driver is enabled for the SDA pin, the output driver will force the line SDA low if the output of the Shift Register or the corresponding bit in the PORT Register is zero.

Otherwise the SDA line will not be driven (i.e., it is released). When the SCL pin output driver is enabled the SCL line will be forced low if the corresponding bit in the PORT Register is zero, or by the start detector. Otherwise the SCL line will not be driven.

The SCL line is held low when a start detector detects a start condition and the output is enabled. Clearing the Start Condition Flag (USISIF) releases the line. The SDA and SCL pin inputs is not affected by enabling this mode. Pull-ups on the SDA and SCL port pin are disabled in Two-wire mode.

1 1

Two-wire mode. Uses SDA and SCL pins.

Same operation as for the Two-wire mode described above, except that the SCL line is also held low when a counter overflow occurs, and is held low until the Counter Overflow Flag

(USIOIF) is cleared.

Note: 1.

The DI and USCK pins are renamed to serial data (SDA) and serial clock (SCL) respectively to avoid confusion between the modes of operation.

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• Bit 3..2 – USICS1..0: Clock Source Select

These bits set the clock source for the shift register and counter. The data output latch ensures that the output is changed at the opposite edge of the sampling of the data input (DI/SDA) when using external clock source (USCK/SCL). When software strobe or Timer/Counter0 compare match clock option is selected, the output latch is transparent and therefore the output is changed immediately. Clearing the USICS1..0 bits enables software strobe option. When using this option, writing a one to the USICLK bit clocks both the shift register and the counter. For external clock source (USICS1 = 1), the USICLK bit is no longer used as a strobe, but selects between external clocking and software clocking by the USITC strobe bit.

Table 15-2 shows the relationship between the USICS1..0 and USICLK setting and clock source used for the shift register

and the 4-bit counter.

Table 15-2. Relations between the USICS1..0 and USICLK Setting

USICS1

0

0

1

1

0

1

1

USICS0

0

0

1

0

1

0

1

USICLK Shift Register Clock Source

0

1

0

1

X

0

1

No Clock

Software clock strobe (USICLK)

Timer/Counter0 compare match

External, positive edge

External, negative edge

External, positive edge

External, negative edge

4-bit Counter Clock Source

No Clock

Software clock strobe (USICLK)

Timer/Counter0 compare match

External, both edges

External, both edges

Software clock strobe (USITC)

Software clock strobe (USITC)

• Bit 1 – USICLK: Clock Strobe

Writing a one to this bit location strobes the shift register to shift one step and the counter to increment by one, provided that the USICS1..0 bits are set to zero and by doing so the software clock strobe option is selected. The output will change immediately when the clock strobe is executed, i.e., in the same instruction cycle. The value shifted into the shift register is sampled the previous instruction cycle. The bit will be read as zero.

When an external clock source is selected (USICS1 = 1), the USICLK function is changed from a clock strobe to a clock select register. Setting the USICLK bit in this case will select the USITC strobe bit as clock source for the 4-bit counter (see

Table 15-2 on page 97 ).

• Bit 0 – USITC: Toggle Clock Port Pin

Writing a one to this bit location toggles the USCK/SCL value either from 0 to 1, or from 1 to 0. The toggling is independent of the setting in the data direction register, but if the PORT value is to be shown on the pin the DDRE4 must be set as output

(to one). This feature allows easy clock generation when implementing master devices. The bit will be read as zero.

When an external clock source is selected (USICS1 = 1) and the USICLK bit is set to one, writing to the USITC strobe bit will directly clock the 4-bit counter. This allows an early detection of when the transfer is done when operating as a master device.

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16.

Analog Comparator

The analog comparator compares the input values on the positive pin AIN0 and negative pin AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on the negative pin AIN1, the analog comparator output, ACO, is set. The comparator can trigger a separate interrupt, exclusive to the analog comparator. The user can select interrupt triggering on

comparator output rise, fall or toggle. A block diagram of the comparator and its surrounding logic is shown in Figure 16-1

.

Figure 16-1. Analog Comparator Block Diagram

(2)

Bandgap

Reference

VCC

ACBG

ACD

ACIE

AIN0

AIN1

+

-

Interrupt

Select

Analog

Comparator

IRQ

ACI

ACIS1 ACIS0

ACME

ADEN

ACO

ADC Multiplexer

Output

(1)

Notes: 1.

See

Table 16-2 on page 100

.

2.

Refer to

Figure 1 on page 2 and

Table 9-5 on page 52

for analog comparator pin placement.

16.1

ADC Control and Status Register B – ADCSRB

Bit

Read/Write

Initial Value

7

BIN

R

0

6

ACME

R/W

0

5

IPR

R

0

R

0

4

R

0

3

2

ADTS2

R/W

0

1 0

ADTS1 ADTS0 ADCSRB

R/W

0

R/W

0

• Bit 6 – ACME: Analog Comparator Multiplexer Enable

When this bit is written logic one and the ADC is switched off (ADEN in ADCSRA is zero), the ADC multiplexer selects the negative input to the analog comparator. When this bit is written logic zero, AIN1 is applied to the negative input of the analog comparator. For a detailed description of this bit, see

Section 16.3 “Analog Comparator Multiplexed Input” on page

100

.

16.2

Analog Comparator Control and Status Register – ACSR

Bit

Read/Write

Initial Value

7

ACD

R/W

0

6

ACBG

R/W

0

5

ACO

R

N/A

4

ACI

R/W

0

3

ACIE

R/W

0

2

R

0

1

ACIS1

R/W

0

0

ACIS0

R/W

0

ACSR

• Bit 7 – ACD: Analog Comparator Disable

When this bit is written logic one, the power to the analog comparator is switched off. This bit can be set at any time to turn off the analog comparator.

This will reduce power consumption in Active and idle mode. When changing the ACD bit, the analog comparator interrupt must be disabled by clearing the ACIE bit in ACSR. Otherwise an interrupt can occur when the bit is changed.

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• Bit 6 – ACBG: Analog Comparator Bandgap Select

When this bit is set an internal 1.1V/2.56V reference voltage replaces the positive input to the analog comparator. The selection of the internal voltage reference is done by writing the REFS2..0 bits in ADMUX register. When this bit is cleared,

AIN0 is applied to the positive input of the analog comparator.

• Bit 5 – ACO: Analog Comparator Output

The output of the analog comparator is synchronized and then directly connected to ACO. The synchronization introduces a delay of 1 - 2 clock cycles.

• Bit 4 – ACI: Analog Comparator Interrupt Flag

This bit is set by hardware when a comparator output event triggers the interrupt mode defined by ACIS1 and ACIS0. The analog comparator interrupt routine is executed if the ACIE bit is set and the I-bit in SREG is set. ACI is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, ACI is cleared by writing a logic one to the flag.

• Bit 3 – ACIE: Analog Comparator Interrupt Enable

When the ACIE bit is written logic one and the I-bit in the status register is set, the analog comparator interrupt is activated.

When written logic zero, the interrupt is disabled.

• Bit 2 – Res: Reserved Bit

This bit is a reserved bit in the Atmel

®

ATtiny25/45/85 and will always read as zero.

• Bits 1, 0 – ACIS1, ACIS0: Analog Comparator Interrupt Mode Select

These bits determine which comparator events that trigger the analog comparator interrupt. The different settings are shown

in Table 16-1

.

Table 16-1. ACIS1/ACIS0 Settings

ACIS1

0

0

1

1

ACIS0

0

1

0

1

Interrupt Mode

Comparator interrupt on output toggle.

Reserved

Comparator interrupt on falling output edge.

Comparator interrupt on rising output edge.

When changing the ACIS1/ACIS0 bits, the analog comparator interrupt must be disabled by clearing its interrupt enable bit in the ACSR register. Otherwise an interrupt can occur when the bits are changed.

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16.3

Analog Comparator Multiplexed Input

It is possible to select any of the ADC3..0 pins to replace the negative input to the analog comparator. The ADC multiplexer is used to select this input, and consequently, the ADC must be switched off to utilize this feature. If the analog comparator multiplexer enable bit (ACME in ADCSRB) is set and the ADC is switched off (ADEN in ADCSRA is zero), MUX1..0 in

ADMUX select the input pin to replace the negative input to the analog comparator, as shown in

Table 16-2 . If ACME is

cleared or ADEN is set, AIN1 is applied to the negative input to the analog comparator.

Table 16-2. Analog Comparator Multiplexed Input

ACME

0

1

1

1

1

1

ADEN

x

1

0

0

0

0

MUX1..0

xx xx

00

01

10

11

Analog Comparator Negative Input

AIN1

AIN1

ADC0

ADC1

ADC2

ADC3

16.3.1 Digital Input Disable Register 0 – DIDR0

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5 4 3 2 1 0

ADC0D ADC2D ADC3D ADC1D AIN1D AIN0D

R/W

0

R/W

0

R/W

0

R/W

0

R/W

0

R/W

0

DIDR0

• Bits 1, 0 – AIN1D, AIN0D: AIN1, AIN0 Digital Input Disable

When this bit is written logic one, the digital input buffer on the AIN1/0 pin is disabled. The corresponding PIN register bit will always read as zero when this bit is set. When an analog signal is applied to the AIN1/0 pin and the digital input from this pin is not needed, this bit should be written logic one to reduce power consumption in the digital input buffer.

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17.

Analog to Digital Converter

17.1

Features

10-bit resolution

0.5 LSB integral non-linearity

±2 LSB absolute accuracy

65 - 260µs conversion time

Up to 15kSPS at maximum resolution

Four multiplexed single ended input channels

Two differential input channels with selectable gain

Temperature sensor input channel

Optional left adjustment for ADC result readout

0 - V

CC

ADC input voltage range

Selectable 1.1V / 2.56V ADC voltage reference

Free running or single conversion mode

ADC start conversion by auto triggering on interrupt sources

Interrupt on ADC conversion complete

Sleep mode noise canceler

Unipolar/bibilar input mode

Input polarity reversal mode

The Atmel

®

ATtiny25/45/85 features a 10-bit successive approximation ADC. The ADC is connected to a 4-channel analog multiplexer which allows one differential voltage input and four single-ended voltage inputs constructed from the pins of port

B. The differential input (PB3, PB4 or PB2, PB5) is equipped with a programmable gain stage, providing amplification step of

26dB (20x) on the differential input voltage before the A/D conversion. The single-ended voltage inputs refer to 0V (GND).

The ADC contains a sample and hold circuit which ensures that the input voltage to the ADC is held at a constant level

during conversion. A block diagram of the ADC is shown in Figure 17-1 on page 102 .

Internal voltage references of nominally 1.1V or 2.56V are provided on-chip and these voltage references can optionally be externally decoupled at the AREF (PB0) pin by a capacitor, for better noise performance. Alternatively, V

CC

can be used as voltage reference for single ended channels. There is also an option to use an external voltage reference and turn-off the internal voltage reference. These options are selected using the REFS2..0 bits of the ADMUX control register.

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Figure 17-1. Analog to Digital Converter Block Schematic

ADC Conversion

Complete IRQ

8-bit Data Bus

ADC CTRL and Status B

Register (ADCSRB)

BIN

IPR

ADC Multiplexer

Select (ADMUX)

MUX Decoder

Interrupt

Flags

ADTS[2:0]

ADC CTRL and Status A

Register (ADCSRA)

Trigger

Select

Prescaler

START

15 0

ADC Data Register

(ADCH/ADCL)

ADC3

ADC2

ADC1

ADC0

V

CC

AREF

Internal

1.1V/2.56V

Reference

Temperature

Sensor

ADC4

POS.

Input

MUX

10-bit DAC

Single Ended/ Differential Selection

Sample and Hold

Comparator

-

+

+

-

Gain

Amplifier

Conversion Logic

ADC

MULTIPLEXER

OUTPUT

NEG.

Input

MUX

17.2

Operation

The ADC converts an analog input voltage to a 10-bit digital value through successive approximation. The minimum value represents GND and the maximum value represents the voltage on V

CC

1.1V/2.56V voltage reference.

, the voltage on the AREF pin or an internal

The voltage reference for the ADC may be selected by writing to the REFS2..0 bits in ADMUX. The VCC supply, the AREF pin or an internal 1.1V/2.56V voltage reference may be selected as the ADC voltage reference. Optionally the internal

1.1V/2.56V voltage reference may be decoupled by an external capacitor at the AREF pin to improve noise immunity.

The analog input channel and differential gain are selected by writing to the MUX3..0 bits in ADMUX. Any of the four ADC input pins ADC3..0 can be selected as single ended inputs to the ADC. ADC2 or ADC0 can be selected as positive input and

ADC0, ADC1, ADC2 or ADC3 can be selected as negative input to the differential gain amplifier.

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If differential channels are selected, the differential gain stage amplifies the voltage difference between the selected input pair by the selected gain factor, 1x or 20x, according to the setting of the MUX3..0 bits in ADMUX. This amplified value then becomes the analog input to the ADC. If single ended channels are used, the gain amplifier is bypassed altogether.

If ADC0 or ADC2 is selected as both the positive and negative input to the differential gain amplifier

(ADC0-ADC0 or ADC2-ADC2), the remaining offset in the gain stage and conversion circuitry can be measured directly as the result of the conversion. This figure can be subtracted from subsequent conversions with the same gain setting to reduce offset error to below 1 LSW.

The on-chip temperature sensor is selected by writing the code “1111” to the MUX3..0 bits in ADMUX register when the

ADC4 channel is used as an ADC input.

The ADC is enabled by setting the ADC Enable bit, ADEN in ADCSRA. Voltage reference and input channel selections will not go into effect until ADEN is set. The ADC does not consume power when ADEN is cleared, so it is recommended to switch off the ADC before entering power saving sleep modes.

The ADC generates a 10-bit result which is presented in the ADC data registers, ADCH and ADCL. By default, the result is presented right adjusted, but can optionally be presented left adjusted by setting the ADLAR bit in ADMUX.

If the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read ADCH. Otherwise, ADCL must be read first, then ADCH, to ensure that the content of the data registers belongs to the same conversion. Once ADCL is read, ADC access to data registers is blocked. This means that if ADCL has been read, and a conversion completes before

ADCH is read, neither register is updated and the result from the conversion is lost. When ADCH is read, ADC access to the

ADCH and ADCL registers is re-enabled.

The ADC has its own interrupt which can be triggered when a conversion completes. When ADC access to the data registers is prohibited between reading of ADCH and ADCL, the interrupt will trigger even if the result is lost.

17.3

Starting a Conversion

A single conversion is started by writing a logical one to the ADC start conversion bit, ADSC. This bit stays high as long as the conversion is in progress and will be cleared by hardware when the conversion is completed. If a different data channel is selected while a conversion is in progress, the ADC will finish the current conversion before performing the channel change.

Alternatively, a conversion can be triggered automatically by various sources. Auto triggering is enabled by setting the ADC auto trigger enable bit, ADATE in ADCSRA. The trigger source is selected by setting the ADC trigger select bits, ADTS in

ADCSRB (see description of the ADTS bits for a list of the trigger sources). When a positive edge occurs on the selected trigger signal, the ADC prescaler is reset and a conversion is started. This provides a method of starting conversions at fixed intervals. If the trigger signal still is set when the conversion completes, a new conversion will not be started. If another positive edge occurs on the trigger signal during conversion, the edge will be ignored. Note that an interrupt flag will be set even if the specific interrupt is disabled or the global interrupt enable bit in SREG is cleared. A conversion can thus be triggered without causing an interrupt. However, the interrupt flag must be cleared in order to trigger a new conversion at the next interrupt event.

Figure 17-2. ADC Auto Trigger Logic

ADTS[2:0]

Prescaler

START CLK

ADC

ADIF

SOURCE 1

.

.

.

.

SOURCE n

ADSC

Edge

Detector

ADATE

Conversion

Logic

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Using the ADC interrupt flag as a trigger source makes the ADC start a new conversion as soon as the ongoing conversion has finished. The ADC then operates in free running mode, constantly sampling and updating the ADC data register. The first conversion must be started by writing a logical one to the ADSC bit in ADCSRA. In this mode the ADC will perform successive conversions independently of whether the ADC interrupt flag, ADIF is cleared or not.

If auto triggering is enabled, single conversions can be started by writing ADSC in ADCSRA to one. ADSC can also be used to determine if a conversion is in progress. The ADSC bit will be read as one during a conversion, independently of how the conversion was started.

17.4

Prescaling and Conversion Timing

Figure 17-3. ADC Prescaler

ADEN

START

CK

Reset

7-bit ADC Prescaler

ADPS0

ADPS1

ADPS2

ADC Clock Source

By default, the successive approximation circuitry requires an input clock frequency between 50kHz and 200kHz to get maximum resolution. If a lower resolution than 10 bits is needed, the input clock frequency to the ADC can be higher than

200kHz to get a higher sample rate. It is not recommended to use a higher input clock frequency than 1MHz.

The ADC module contains a prescaler, which generates an acceptable ADC clock frequency from any CPU frequency above

100kHz. The prescaling is set by the ADPS bits in ADCSRA. The prescaler starts counting from the moment the ADC is switched on by setting the ADEN bit in ADCSRA. The prescaler keeps running for as long as the ADEN bit is set, and is continuously reset when ADEN is low.

When initiating a single ended conversion by setting the ADSC bit in ADCSRA, the conversion starts at the following rising edge of the ADC clock cycle.

A normal conversion takes 13 ADC clock cycles. The first conversion after the ADC is switched on (ADEN in ADCSRA is set) takes 25 ADC clock cycles in order to initialize the analog circuitry.

The actual sample-and-hold takes place 1.5 ADC clock cycles after the start of a normal conversion and 14.5 ADC clock cycles after the start of an first conversion. When a conversion is complete, the result is written to the ADC data registers, and ADIF is set. In single conversion mode, ADSC is cleared simultaneously. The software may then set ADSC again, and a new conversion will be initiated on the first rising ADC clock edge.

When auto triggering is used, the prescaler is reset when the trigger event occurs. This assures a fixed delay from the trigger event to the start of conversion. In this mode, the sample-and-hold takes place two ADC clock cycles after the rising edge on the trigger source signal. Three additional CPU clock cycles are used for synchronization logic.

In free running mode, a new conversion will be started immediately after the conversion completes, while ADSC remains

high. For a summary of conversion times, see Table 17-1 on page 106 .

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Figure 17-4. ADC Timing Diagram, First Conversion (Single Conversion Mode)

First Conversion

Cycle Number

ADC Clock

ADEN

ADSC

ADIF

ADCH

ADCL

1 2 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Next

Conversion

1 2 3

Sign and MSB of Result

LSB of Result

MUX and REFS

Update

Sample and Hold

Conversion

Complete

MUX and REFS

Update

Figure 17-5. ADC Timing Diagram, Single Conversion

One Conversion Next Conversion

Cycle Number

ADC Clock

ADSC

ADIF

ADCH

ADCL

1 2 3 4 5 6 7 8 9 10 11 12 13

Sample and Hold

MUX and REFS

Update

Conversion

Complete

1 2 3

Sign and MSB of Result

LSB of Result

MUX and REFS

Update

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Figure 17-6. ADC Timing Diagram, Auto Triggered Conversion

One Conversion Next Conversion

Cycle Number

ADC Clock

Trigger

Source

ADATE

ADIF

ADCH

ADCL

1 2 3 4 5 6 7 8 9 10 11 12 13

Prescaler

Reset

Sample and Hold

MUX and REFS

Update

Conversion

Complete

Figure 17-7. ADC Timing Diagram, Free Running Conversion

One Conversion Next Conversion

1 2

Sign and MSB of Result

LSB of Result

Prescaler

Reset

Table 17-1. ADC Conversion Time

Condition

First conversion

Normal conversions

Auto triggered conversions

Cycle Number

ADC Clock

ADSC

ADIF

ADCH

ADCL

11 12 13 1 2 3 4

Sign and MSB of Result

LSB of Result

Conversion

Complete

Sample and Hold

MUX and REFS

Update

Sample and Hold (Cycles from

Start of Conversion)

13.5

1.5

2

Total Conversion Time (Cycles)

25

13

13.5

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17.5

Changing Channel or Reference Selection

The MUX3..0 and REFS2..0 bits in the ADMUX register are single buffered through a temporary register to which the CPU has random access. This ensures that the channels and voltage reference selection only takes place at a safe point during the conversion. The channel and voltage reference selection is continuously updated until a conversion is started. Once the conversion starts, the channel and voltage reference selection is locked to ensure a sufficient sampling time for the ADC.

Continuous updating resumes in the last ADC clock cycle before the conversion completes (ADIF in ADCSRA is set). Note that the conversion starts on the following rising ADC clock edge after ADSC is written. The user is thus advised not to write new channel or voltage reference selection values to ADMUX until one ADC clock cycle after ADSC is written.

If auto triggering is used, the exact time of the triggering event can be indeterministic. Special care must be taken when updating the ADMUX register, in order to control which conversion will be affected by the new settings.

If both ADATE and ADEN is written to one, an interrupt event can occur at any time. If the ADMUX register is changed in this period, the user cannot tell if the next conversion is based on the old or the new settings. ADMUX can be safely updated in the following ways: a.

When ADATE or ADEN is cleared.

b.

During conversion, minimum one ADC clock cycle after the trigger event.

c.

After a conversion, before the Interrupt Flag used as trigger source is cleared.

When updating ADMUX in one of these conditions, the new settings will affect the next ADC conversion.

17.5.1 ADC Input Channels

When changing channel selections, the user should observe the following guidelines to ensure that the correct channel is selected:

In single conversion mode, always select the channel before starting the conversion. The channel selection may be changed one ADC clock cycle after writing one to ADSC. However, the simplest method is to wait for the conversion to complete before changing the channel selection.

In free running mode, always select the channel before starting the first conversion. The channel selection may be changed one ADC clock cycle after writing one to ADSC. However, the simplest method is to wait for the first conversion to complete, and then change the channel selection. Since the next conversion has already started automatically, the next result will reflect the previous channel selection. Subsequent conversions will reflect the new channel selection.

17.5.2 ADC Voltage Reference

The voltage reference for the ADC (V

REF

) indicates the conversion range for the ADC. Single ended channels that exceed

V

REF

will result in codes close to 0x3FF. V

REF

can be selected as either V

CC

, or internal 1.1V/2.56V voltage reference, or external AREF pin. The first ADC conversion result after switching voltage reference source may be inaccurate, and the user is advised to discard this result.

17.6

ADC Noise Canceler

The ADC features a noise canceler that enables conversion during sleep mode to reduce noise induced from the CPU core and other I/O peripherals. The noise canceler can be used with ADC noise reduction and Idle mode. To make use of this feature, the following procedure should be used: a.

Make sure that the ADC is enabled and is not busy converting. Single conversion mode must be selected and the

ADC conversion complete interrupt must be enabled.

b.

Enter ADC noise reduction mode (or idle mode). The ADC will start a conversion once the CPU has been halted.

c.

If no other interrupts occur before the ADC conversion completes, the ADC interrupt will wake up the CPU and execute the ADC conversion complete interrupt routine. If another interrupt wakes up the CPU before the ADC conversion is complete, that interrupt will be executed, and an ADC conversion complete interrupt request will be generated when the ADC conversion completes. The CPU will remain in active mode until a new sleep command is executed.

Note that the ADC will not be automatically turned off when entering other sleep modes than Idle mode and ADC noise reduction mode. The user is advised to write zero to ADEN before entering such sleep modes to avoid excessive power consumption.

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17.6.1 Analog Input Circuitry

The analog input circuitry for single ended channels is illustrated in Figure 17-8. An analog source applied to ADCn is

subjected to the pin capacitance and input leakage of that pin, regardless of whether that channel is selected as input for the

ADC. When the channel is selected, the source must drive the S/H capacitor through the series resistance (combined resistance in the input path).

The ADC is optimized for analog signals with an output impedance of approximately 10 k

Ω

or less. If such a source is used, the sampling time will be negligible. If a source with higher impedance is used, the sampling time will depend on how long time the source needs to charge the S/H capacitor, with can vary widely. The user is recommended to only use low impedant sources with slowly varying signals, since this minimizes the required charge transfer to the S/H capacitor.

Signal components higher than the nyquist frequency (f

ADC

/2) should not be present to avoid distortion from unpredictable signal convolution. The user is advised to remove high frequency components with a low-pass filter before applying the signals as inputs to the ADC.

Figure 17-8. Analog Input Circuitry

I

IH

ADCn

I

IL

1 to 100kΩ

C

S/H

= 14pF

V

CC

/2

17.6.2 Analog Noise Canceling Techniques

Digital circuitry inside and outside the device generates EMI which might affect the accuracy of analog measurements. If conversion accuracy is critical, the noise level can be reduced by applying the following techniques: a.

Keep analog signal paths as short as possible. Make sure analog tracks run over the analog ground plane, and keep them well away from high-speed switching digital tracks.

b.

Use the ADC noise canceler function to reduce induced noise from the CPU.

c.

If any port pins are used as digital outputs, it is essential that these do not switch while a conversion is in progress.

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17.6.3 ADC Accuracy Definitions

An n-bit single-ended ADC converts a voltage linearly between GND and V

REF as 0, and the highest code is read as 2 n

–1.

in 2 n

steps (LSBs). The lowest code is read

Several parameters describe the deviation from the ideal behavior:

Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal transition (at 0.5 LSB). Ideal value:

0 LSB.

Figure 17-9. Offset Error

Output Code

Ideal ADC

Actual ADC

Offset

Error

V

REF

Input Voltage

Gain error: After adjusting for offset, the gain error is found as the deviation of the last transition (0x3FE to 0x3FF) compared to the ideal transition (at 1.5 LSB below maximum). Ideal value: 0 LSB

Figure 17-10. Gain Error

Output Code

Gain

Error

Ideal ADC

Actual ADC

V

REF

Input Voltage

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Integral non-linearity (INL): After adjusting for offset and gain error, the INL is the maximum deviation of an actual transition compared to an ideal transition for any code. Ideal value: 0 LSB.

Figure 17-11. Integral Non-linearity (INL)

Output Code

Ideal ADC

Actual ADC

V

REF

Input Voltage

Differential non-linearity (DNL): The maximum deviation of the actual code width (the interval between two adjacent transitions) from the ideal code width (1 LSB). Ideal value: 0 LSB.

Figure 17-12. Differential Non-linearity (DNL)

Output Code

0x3FF

1 LSB

DNL

0x000

0

V

REF

Input Voltage

Quantization error: Due to the quantization of the input voltage into a finite number of codes, a range of input voltages

(1 LSB wide) will code to the same value. Always ±0.5 LSB.

Absolute accuracy: The maximum deviation of an actual (unadjusted) transition compared to an ideal transition for any code. This is the compound effect of offset, gain error, differential error, non-linearity, and quantization error. Ideal value: ±0.5 LSB.

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17.7

ADC Conversion Result

After the conversion is complete (ADIF is high), the conversion result can be found in the ADC result registers (ADCL,

ADCH). The form of the conversion result depends on the type of the conversion as there are three types of conversions: single ended conversion, unipolar differential conversion and bipolar differential conversion.

17.7.1 Single Ended Conversion

For single ended conversion, the result is

ADC

=

IN

×

1024

V

REF where V

IN

is the voltage on the selected input pin and V

REF

the selected voltage reference (see

Table 17-3 on page 112 and

Table 17-4 on page 113 ). 0x000 represents analog ground, and 0x3FF represents the selected voltage reference minus one

LSB. The result is presented in one-sided form, from 0x3FF to 0x000.

17.7.2 Unipolar Differential Conversion

If differential channels and an unipolar input mode are used, the result is

ADC

=

(

POS

V

NEG

V

REF

) ×

1024 where V

POS is the voltage on the positive input pin, V

NEG the voltage on the negative input pin, and V

REF the selected voltage reference (see

Table 17-3 on page 112

and

Table 17-4 on page 113 ). The voltage on the positive pin must always be larger

than the voltage on the negative pin or otherwise the voltage difference is saturated to zero. The result is presented in onesided form, from 0x000 (0d) to 0x3FF (+1023d). The GAIN is either 1x or 20x.

17.7.3 Bipolar Differential Conversion

As default the ADC converter operates in the unipolar input mode, but the bipolar input mode can be selected by writing the

BIN bit in the ADCSRB to one. In the bipolar input mode two-sided voltage differences are allowed and thus the voltage on the negative input pin can also be larger than the voltage on the positive input pin. If differential channels and a bipolar input mode are used, the result is

ADC

=

(

V

V

NEG

)

V

REF

×

512

× where V

POS is the voltage on the positive input pin, V

NEG the voltage on the negative input pin, and V

REF the selected voltage reference. The result is presented in two’s complement form, from 0x200 (–512d) through 0x000 (+0d) to 0x1FF (+511d).

The GAIN is either 1x or 20x.

However, if the signal is not bipolar by nature (9 bits + sign as the 10th bit), this scheme loses one bit of the converter dynamic range. Then, if the user wants to perform the conversion with the maximum dynamic range, the user can perform a quick polarity check of the result and use the unipolar differential conversion with selectable differential input pairs (see the input polarity reversal mode ie. the IPR bit in the

Section 17.7.8 “ADC Control and Status Register B – ADCSRB” on page

115

). When the polarity check is performed, it is sufficient to read the MSB of the result (ADC9 in ADCH). If the bit is one, the result is negative, and if this bit is zero, the result is positive.

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17.7.4 Temperature Measurement (Preliminary description)

The temperature measurement is based on an on-chip temperature sensor that is coupled to a single ended ADC4 channel.

Selecting the ADC4 channel by writing the MUX3..0 bits in ADMUX register to “1111” enables the temperature sensor. The internal 1.1V voltage reference must also be selected for the ADC voltage reference source in the temperature sensor measurement. When the temperature sensor is enabled, the ADC converter can be used in single conversion mode to measure the voltage over the temperature sensor.

The measured voltage has a linear relationship to the temperature as described in Table 17-2

. The voltage sensitivity is approximately 1mV/°C and the accuracy of the temperature measurement is ±10°C after bandgap calibration.

Table 17-2. Temperature versus Sensor Output Voltage (Typical Case)

Temperature/°C

Voltage/mV

–45°C

242mV

+25°C

314mv

+105°C

403mV

The values described in

Table 17-2

are typical values. However, due to the process variation the temperature sensor output voltage varies from one chip to another. To be capable of achieving more accurate results the temperature measurement can be calibrated in the application software. The software calibration requires that a calibration value is measured and stored in a register or EEPROM for each chip, as a part of the production test. The software calibration can be done utilizing the formula:

Temperature = k

×

V

TEMP

+ T

OS where V

TEMP is the ADC reading of the temperature sensor signal, k is a fixed coefficient and T offset value determined and stored into EEPROM as a part of production test.

OS is the temperature sensor

17.7.5 ADC Multiplexer Selection Register – ADMUX

Bit

Read/Write

Initial Value

7 6 5 4

REFS1 REFS0 ADLAR REFS2

R

0

R/W

0

R/W

0

R

0

3

MUX3

R

0

2

MUX2

R

0

1

MUX1

R/W

0

0

MUX0

R/W

0

ADMUX

• Bit 7..6,4 – REFS2..REFS0: Voltage Reference Selection Bits

These bits select the voltage reference (V

REF

) for the ADC, as shown in

Table 17-3 . If these bits are changed during a

conversion, the change will not go in effect until this conversion is complete (ADIF in ADCSR is set). Whenever these bits are changed, the next conversion will take 25 ADC clock cycles. If active channels are used, using V

CC higher than (V

CC

or an external AREF

– 1V) as a voltage reference is not recommended, as this will affect the ADC accuracy.

Table 17-3. Voltage Reference Selections for ADC

REFS2

0

0

0

0

1

REFS1

0

0

1

1

1

REFS0 Voltage Reference (V

REF

) Selection

0

1

V

CC

used as voltage reference, disconnected from PB0 (AREF).

External voltage reference at PB0 (AREF) pin, internal voltage reference turned off.

0

1

0

Internal 1.1V voltage reference without external bypass capacitor, disconnected from PB0 (AREF).

Internal 1.1V voltage reference with external bypass capacitor at PB0 (AREF) pin.

Internal 2.56V voltage reference without external bypass capacitor, disconnected from PB0 (AREF).

(1)

1 1 1

Internal 2.56V voltage reference with external bypass capacitor at PB0 (AREF) pin.

(1)

Note: 1.

The device requires a supply voltage of 3V in order to generate 2.56V reference voltage.

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• Bit 5 – ADLAR: ADC Left Adjust Result

The ADLAR bit affects the presentation of the ADC conversion result in the ADC data register. Write one to ADLAR to left adjust the result. Otherwise, the result is right adjusted. Changing the ADLAR bit will affect the ADC data register

immediately, regardless of any ongoing conversions. For a complete description of this bit, see Section 17.7.7 “The ADC

Data Register – ADCL and ADCH” on page 115

.

• Bits 3:0 – MUX3:0: Analog Channel and Gain Selection Bits

The value of these bits selects which combination of analog inputs are connected to the ADC. In case of differential input

(ADC0 - ADC1 or ADC2 - ADC3), gain selection is also made with these bits. Selecting ADC2 or ADC0 as both inputs to the differential gain stage enables offset measurements. Selecting the single-ended channel ADC4 enables the temperature

sensor. Refer to Table 17-4 on page 113

for details. If these bits are changed during a conversion, the change will not go into effect until this conversion is complete (ADIF in ADCSRA is set).

Table 17-4. Input Channel Selections

MUX3..0

0000

0001

Single Ended Input

ADC0 (PB5)

ADC1 (PB2)

Positive Differential

Input

Negative Differential

Input

0010

0011

0100

0101

(1)

0110

0111

1000

1001

1010

1011

1100

1101

ADC2 (PB4)

ADC3 (PB3)

N/A

1.1V/2.56V

0V

ADC2 (PB3)

ADC2 (PB3)

ADC2 (PB3)

ADC2 (PB3)

ADC0 (PB5)

ADC0 (PB5)

ADC0 (PB5)

ADC0 (PB5)

N/A

ADC2 (PB3)

ADC2 (PB3)

ADC3 (PB4)

ADC3 (PB4)

1110 N/A

1111 ADC4

(2)

Notes: 1.

For offset calibration only. See

Section 17.2 “Operation” on page 102

2.

For temperature sensor

ADC0 (PB5)

ADC0 (PB5)

ADC1 (PB2)

ADC1 (PB2)

N/A

Gain

1x

20x

1x

20x

1x

20x

1x

20x

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17.7.6 ADC Control and Status Register A – ADCSRA

Bit

Read/Write

Initial Value

7 6 5 4

ADEN ADSC ADATE ADIF

R/W R/W R/W R/W

0 0 0 0

3 2 1 0

ADIE ADPS2 ADPS1 ADPS0 ADCSRA

R/W R/W R/W R/W

0 0 0 0

• Bit 7 – ADEN: ADC Enable

Writing this bit to one enables the ADC. By writing it to zero, the ADC is turned off. Turning the ADC off while a conversion is in progress, will terminate this conversion.

• Bit 6 – ADSC: ADC Start Conversion

In single conversion mode, write this bit to one to start each conversion. In free running mode, write this bit to one to start the first conversion.

The first conversion after ADSC has been written after the ADC has been enabled, or if ADSC is written at the same time as the ADC is enabled, will take 25 ADC clock cycles instead of the normal 13. This first conversion performs initialization of the

ADC. ADSC will read as one as long as a conversion is in progress. When the conversion is complete, it returns to zero.

Writing zero to this bit has no effect.

• Bit 5 – ADATE: ADC Auto Trigger Enable

When this bit is written to one, auto triggering of the ADC is enabled. The ADC will start a conversion on a positive edge of the selected trigger signal. The trigger source is selected by setting the ADC trigger select bits, ADTS in ADCSRB.

• Bit 4 – ADIF: ADC Interrupt Flag

This bit is set when an ADC conversion completes and the data registers are updated. The ADC conversion complete interrupt is executed if the ADIE bit and the I-bit in SREG are set. ADIF is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, ADIF is cleared by writing a logical one to the flag. Beware that if doing a read-modify-write on ADCSRA, a pending interrupt can be disabled. This also applies if the SBI and CBI instructions are used.

• Bit 3 – ADIE: ADC Interrupt Enable

When this bit is written to one and the I-bit in SREG is set, the ADC conversion complete interrupt is activated.

• Bits 2:0 – ADPS2:0: ADC Prescaler Select Bits

These bits determine the division factor between the system clock frequency and the input clock to the ADC.

Table 17-5. ADC Prescaler Selections

ADPS2

0

0

1

1

0

0

1

1

ADPS1

0

0

0

0

1

1

1

1

ADPS0

0

1

0

1

0

1

0

1

Division Factor

2

2

4

8

16

32

64

128

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17.7.7 The ADC Data Register – ADCL and ADCH

17.7.7.1 ADLAR = 0

Bit

Read/Write

Initial Value

15

ADC7

R

0

7

R

0

14

ADC6

R

0

6

R

0

13

ADC5

R

0

5

R

0

12

ADC4

R

0

4

R

0

11

ADC3

R

0

3

R

0

10

ADC2

R

0

2

R

0

9

ADC9

ADC1

R

0

1

R

0

8

ADC8

ADC0

R

0

0

R

0

ADCH

ADCL

17.7.7.2 ADLAR = 1

Bit

Read/Write

Initial Value

15

ADC9

ADC1

R

0

7

R

0

14

ADC8

ADC0

R

0

6

R

0

13

ADC7

R

0

5

R

0

12

ADC6

R

0

4

R

0

11

ADC5

R

0

3

R

0

10

ADC4

R

0

2

R

0

9

ADC3

R

0

1

R

0

8

ADC2

R

0

0

R

0

ADCH

ADCL

When an ADC conversion is complete, the result is found in these two registers.

When ADCL is read, the ADC data register is not updated until ADCH is read. Consequently, if the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read ADCH. Otherwise, ADCL must be read first, then ADCH.

The ADLAR bit in ADMUX, and the MUXn bits in ADMUX affect the way the result is read from the registers. If ADLAR is set, the result is left adjusted. If ADLAR is cleared (default), the result is right adjusted.

• ADC9:0: ADC Conversion Result

These bits represent the result from the conversion, as detailed in

Section 17.7 “ADC Conversion Result” on page 111

.

17.7.8 ADC Control and Status Register B – ADCSRB

Bit

Read/Write

Initial Value

7

BIN

R/W

0

6

ACME

R/W

0

5

IPR

R/W

0

R

0

4

R

0

3

2 1 0

ADTS2 ADTS1 ADTS0 ADCSRB

R/W

0

R/W

0

R/W

0

• Bit 7– BIN: Bipolar Input Mode

The gain stage is working in the unipolar mode as default, but the bipolar mode can be selected by writing the BIN bit in the

ADCSRB register. In the unipolar mode only one-sided conversions are supported and the voltage on the positive input must always be larger than the voltage on the negative input. Otherwise the result is saturated to the voltage reference. In the bipolar mode two-sided conversions are supported and the result is represented in the two’s complement form. In the unipolar mode the resolution is 10 bits and the bipolar mode the resolution is 9 bits + 1 sign bit.

• Bit 5 – IPR: Input Polarity Mode

The input polarity mode allows software selectable differential input pairs and full 10 bit ADC resolution, in the unipolar input mode, assuming a pre-determined input polarity. If the input polarity is not known it is actually possible to determine the polarity first by using the bipolar input mode (with 9 bit resolution + 1 sign bit ADC measurement). And once determined, set or clear the polarity reversal bit, as needed, for a succeeding 10 bit unipolar measurement.

• Bits 4..3 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and will always read as zero.

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• Bits 2:0 – ADTS2:0: ADC Auto Trigger Source

If ADATE in ADCSRA is written to one, the value of these bits selects which source will trigger an ADC conversion. If ADATE is cleared, the ADTS2:0 settings will have no effect. A conversion will be triggered by the rising edge of the selected interrupt flag. Note that switching from a trigger source that is cleared to a trigger source that is set, will generate a positive edge on the trigger signal. If ADEN in ADCSRA is set, this will start a conversion. Switching to free running mode (ADTS[2:0]=0) will not cause a trigger event, even if the ADC interrupt flag is set.

Table 17-6. ADC Auto Trigger Source Selections

ADTS2

0

0

1

1

0

0

1

ADTS1

0

0

1

1

0

0

1

ADTS0

0

1

0

1

0

1

0

Trigger Source

Free running mode

Analog comparator

External interrupt request 0

Timer/Counter compare match A

Timer/Counter overflow

Timer/Counter compare match B

Pin change interrupt request

17.7.9 Digital Input Disable Register 0 – DIDR0

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5 4 3 2

ADC0D ADC2D ADC3D ADC1D

R/W R/W R/W R/W

0 0 0 0

1

AIN1D

R/W

0

0

AIN0D

R/W

0

DIDR0

• Bits 5..2 – ADC3D..ADC0D: ADC3..0 Digital Input Disable

When this bit is written logic one, the digital input buffer on the corresponding ADC pin is disabled. The corresponding PIN register bit will always read as zero when this bit is set. When an analog signal is applied to the ADC3..0 pin and the digital input from this pin is not needed, this bit should be written logic one to reduce power consumption in the digital input buffer.

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18.

debugWIRE On-chip Debug System

18.1

Features

Complete program flow control

Emulates all on-chip functions, both digital and analog, except RESET pin

Real-time operation

Symbolic debugging support (both at C and assembler source level, or for other HLLs)

Unlimited number of program break points (using software break points)

Non-intrusive operation

Electrical characteristics identical to real device

Automatic configuration system

High-speed operation

Programming of non-volatile memories

18.2

Overview

The debugWIRE on-chip debug system uses a one-wire, bi-directional interface to control the program flow, execute AVR

® instructions in the CPU and to program the different non-volatile memories.

18.3

Physical Interface

When the debugWIRE enable (DWEN) fuse is programmed and lock bits are unprogrammed, the debugWIRE system within the target device is activated. The RESET port pin is configured as a wire-AND (open-drain) bi-directional I/O pin with pull-up enabled and becomes the communication gateway between target and emulator.

Figure 18-1. The debugWIRE Setup

1.8 to 5.5V

VCC dw dw (RESET)

GND

Figure 18-1 shows the schematic of a target MCU, with debugWIRE enabled, and the emulator connector. The system clock

is not affected by debugWIRE and will always be the clock source selected by the CKSEL fuses.

When designing a system where debugWIRE will be used, the following observations must be made for correct operation:

Pull-up resistor on the dW/(RESET) line must be in the range of 10k to 20k

Ω

. However, the pull-up resistor is optional.

Connecting the RESET pin directly to V

CC

will not work.

Capacitors inserted on the RESET pin must be disconnected when using debugWire.

All external reset sources must be disconnected.

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18.4

Software Break Points

debugWIRE supports program memory break points by the AVR

®

break instruction. Setting a break point in AVR Studio

®

will insert a BREAK instruction in the program memory. The instruction replaced by the BREAK instruction will be stored. When program execution is continued, the stored instruction will be executed before continuing from the program memory. A break can be inserted manually by putting the BREAK instruction in the program.

The flash must be re-programmed each time a break point is changed. This is automatically handled by AVR Studio through the debugWIRE interface. The use of break points will therefore reduce the flash data retention. Devices used for debugging purposes should not be shipped to end customers.

18.5

Limitations of debugWIRE

The debugWIRE communication pin (dW) is physically located on the same pin as external reset (RESET). An external reset source is therefore not supported when the debugWIRE is enabled.

The debugWIRE system accurately emulates all I/O functions when running at full speed, i.e., when the program in the CPU is running. When the CPU is stopped, care must be taken while accessing some of the I/O registers via the debugger (AVR studio).

A programmed DWEN fuse enables some parts of the clock system to be running in all sleep modes. This will increase the power consumption while in sleep. Thus, the DWEN fuse should be disabled when debugWire is not used.

18.6

debugWIRE Related Register in I/O Memory

The following section describes the registers used with the debugWire.

18.6.1 debugWire Data Register – DWDR

Bit

Read/Write

Initial Value

7

R/W

0

6

R/W

0

5

R/W

0

4 3

DWDR[7:0]

R/W R/W

0 0

2

R/W

0

1

R/W

0

0

R/W

0

DWDR

The DWDR register provides a communication channel from the running program in the MCU to the debugger. This register is only accessible by the debugWIRE and can therefore not be used as a general purpose register in the normal operations.

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19.

Self-Programming the Flash

The device provides a self-programming mechanism for downloading and uploading program code by the MCU itself. The self-programming can use any available data interface and associated protocol to read code and write (program) that code into the program memory.

The program memory is updated in a page by page fashion. Before programming a page with the data stored in the temporary page buffer, the page must be erased. The temporary page buffer is filled one word at a time using SPM and the buffer can be filled either before the page erase command or between a page erase and a page write operation:

Alternative 1, fill the buffer before a page erase

Fill temporary page buffer

Perform a page erase

Perform a page write

Alternative 2, fill the buffer after page erase

Perform a page erase

Fill temporary page buffer

Perform a page write

If only a part of the page needs to be changed, the rest of the page must be stored (for example in the temporary page buffer) before the erase, and then be re-written. When using alternative 1, the boot loader provides an effective read-modify-write feature which allows the user software to first read the page, do the necessary changes, and then write back the modified data. If alternative 2 is used, it is not possible to read the old data while loading since the page is already erased. The temporary page buffer can be accessed in a random sequence. It is essential that the page address used in both the page erase and page write operation is addressing the same page.

19.1

Performing Page Erase by SPM

To execute page erase, set up the address in the Z-pointer, write “00000011” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored. The page address must be written to PCPAGE in the

Z-register. Other bits in the Z-pointer will be ignored during this operation.

The CPU is halted during the page erase operation.

19.2

Filling the Temporary Buffer (Page Loading)

To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write “00000001” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The content of PCWORD in the Z-register is used to address the data in the temporary buffer. The temporary buffer will auto-erase after a Page Write operation or by writing the CTPB bit in SPMCSR. It is also erased after a system reset. Note that it is not possible to write more than one time to each address without erasing the temporary buffer.

If the EEPROM is written in the middle of an SPM page load operation, all data loaded will be lost.

19.3

Performing a Page Write

To execute page write, set up the address in the Z-pointer, write “00000101” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored. The page address must be written to PCPAGE. Other bits in the Z-pointer must be written to zero during this operation.

The CPU is halted during the page write operation.

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19.4

Addressing the Flash During Self-Programming

The Z-pointer is used to address the SPM commands.

Bit

ZH (R31)

ZL (R30)

15

Z15

Z7

7

14

Z14

Z6

6

13

Z13

Z5

5

12

Z12

Z4

4

11

Z11

Z3

3

10

Z10

Z2

2

9

Z9

Z1

1

8

Z8

Z0

0

Since the flash is organized in pages (see Table 20-6 on page 126 ), the program counter can be treated as having two

different sections. One section, consisting of the least significant bits, is addressing the words within a page, while the most significant bits are addressing the pages. This is shown in

Figure 19-1 . Note that the page erase and page write operations

are addressed independently. Therefore it is of major importance that the software addresses the same page in both the page erase and page write operation.

The LPM instruction uses the Z-pointer to store the address. Since this instruction addresses the flash byte-by-byte, also the

LSB (bit Z0) of the Z-pointer is used.

Figure 19-1. Addressing the Flash During SPM

(1)

Bit

Z-register

15 ZPCMSB

Program

Counter

PCMSB

PCPAGE

Page Address within the Flash

ZPAGEMSB 1 0

0

PAGEMSB

PCWORD

Word Address within a Page

Program Memory

Page

Page

Instruction Word

PCWORD[PAGEMSB:0]

00

01

02

PAGEEND

Note: 1.

The different variables used in Figure 19-1

are listed in Table 20-6 on page 126 .

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19.4.1 Store Program Memory Control and Status Register – SPMCSR

The store program memory control and status register contains the control bits needed to control the program memory operations.

Bit

Read/Write

Initial Value

7

R

0

6

R

0

5

R

0

4

CTPB

R/W

0

3

RFLB

R/W

0

2 1 0

PGWRT PGERS SPMEN SPMCSR

R/W R/W R/W

0 0 0

• Bits 7..5 – Res: Reserved Bits

These bits are reserved bits in the Atmel

®

ATtiny25/45/85 and always read as zero.

• Bit 4 – CTPB: Clear Temporary Page Buffer

If the CTPB bit is written while filling the temporary page buffer, the temporary page buffer will be cleared and the data will be lost.

• Bit 3 – RFLB: Read Fuse and Lock Bits

An LPM instruction within three cycles after RFLB and SPMEN are set in the SPMCSR register, will read either the lock bits or the fuse bits (depending on Z0 in the Z-pointer) into the destination register. See

Section 19.4.2 “EEPROM Write Prevents

Writing to SPMCSR” on page 121

for details.

• Bit 2 – PGWRT: Page Write

If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes page write, with the data stored in the temporary buffer. The page address is taken from the high part of the Z-pointer. The data in R1 and R0 are ignored. The PGWRT bit will auto-clear upon completion of a page Write, or if no SPM instruction is executed within four clock cycles. The CPU is halted during the entire page write operation.

• Bit 1 – PGERS: Page Erase

If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes page erase. The page address is taken from the high part of the Z-pointer. The data in R1 and R0 are ignored. The PGERS bit will auto-clear upon completion of a page erase, or if no SPM instruction is executed within four clock cycles. The CPU is halted during the entire page write operation.

• Bit 0 – SPMEN: Store Program Memory Enable

This bit enables the SPM instruction for the next four clock cycles. If written to one together with either CTPB, RFLB,

PGWRT, or PGERS, the following SPM instruction will have a special meaning, see description above. If only SPMEN is written, the following SPM instruction will store the value in R1:R0 in the temporary page buffer addressed by the Z-pointer.

The LSB of the Z-pointer is ignored. The SPMEN bit will auto-clear upon completion of an SPM instruction, or if no SPM instruction is executed within four clock cycles. During page erase and page write, the SPMEN bit remains high until the operation is completed.

Writing any other combination than “10001”, “01001”, “00101”, “00011” or “00001” in the lower five bits will have no effect.

19.4.2 EEPROM Write Prevents Writing to SPMCSR

Note that an EEPROM write operation will block all software programming to flash. Reading the fuses and lock bits from software will also be prevented during the EEPROM write operation. It is recommended that the user checks the status bit

(EEWE) in the EECR register and verifies that the bit is cleared before writing to the SPMCSR register.

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19.4.3 Reading the Fuse and Lock Bits from Software

It is possible to read both the fuse and lock bits from software. To read the lock bits, load the Z-pointer with 0x0001 and set the RFLB and SPMEN bits in SPMCSR. When an LPM instruction is executed within three CPU cycles after the RFLB and

SPMEN bits are set in SPMCSR, the value of the lock bits will be loaded in the destination register. The RFLB and SPMEN bits will auto-clear upon completion of reading the lock bits or if no LPM instruction is executed within three CPU cycles or no

SPM instruction is executed within four CPU cycles. When RFLB and SPMEN are cleared, LPM will work as described in the

Instruction set Manual.

Bit

Rd

7

6

5

4

3

2

1

LB2

0

LB1

The algorithm for reading the fuse low byte is similar to the one described above for reading the lock bits. To read the fuse low byte, load the Z-pointer with 0x0000 and set the RFLB and SPMEN bits in SPMCSR. When an LPM instruction is executed within three cycles after the RFLB and SPMEN bits are set in the SPMCSR, the value of the fuse low byte (FLB) will be loaded in the destination register as shown below. Refer to

Table 20-5 on page 125

for a detailed description and mapping of the fuse low byte.

Bit

Rd

7

FLB7

6

FLB6

5

FLB5

4

FLB4

3

FLB3

2

FLB2

1

FLB1

0

FLB0

Similarly, when reading the fuse high byte, load 0x0003 in the Z-pointer. When an LPM instruction is executed within three cycles after the RFLB and SPMEN bits are set in the SPMCSR, the value of the fuse high byte (FHB) will be loaded in the destination register as shown below. Refer to

Table 20-4 for detailed description and mapping of the fuse high byte.

Bit

Rd

7

FHB7

6

FHB6

5

FHB5

4

FHB4

3

FHB3

2

FHB2

1

FHB1

0

FHB0

Fuse and lock bits that are programmed, will be read as zero. Fuse and lock bits that are unprogrammed, will be read as one.

19.4.4 Preventing Flash Corruption

During periods of low V

CC

, the flash program can be corrupted because the supply voltage is too low for the CPU and the flash to operate properly. These issues are the same as for board level systems using the flash, and the same design solutions should be applied.

A flash program corruption can be caused by two situations when the voltage is too low. First, a regular write sequence to the flash requires a minimum voltage to operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the supply voltage for executing instructions is too low.

Flash corruption can easily be avoided by following these design recommendations (one is sufficient):

1.

Keep the AVR

®

RESET active (low) during periods of insufficient power supply voltage. This can be done by enabling the internal brown-out detector (BOD) if the operating voltage matches the detection level. If not, an external low V

CC

reset protection circuit can be used. If a reset occurs while a write operation is in progress, the write operation will be completed provided that the power supply voltage is sufficient.

2.

Keep the AVR core in power-down sleep mode during periods of low V

CC

. This will prevent the CPU from attempting to decode and execute instructions, effectively protecting the SPMCSR register and thus the flash from unintentional writes.

19.4.5 Programming Time for Flash when Using SPM

The calibrated RC oscillator is used to time flash accesses.

Table 19-1 shows the typical programming time for flash

accesses from the CPU.

Table 19-1. SPM Programming Time

Symbol

Flash write (page erase, page write, and write lock bits by SPM)

Min Programming Time

3.7ms

Max Programming Time

4.5ms

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20.

Memory Programming

This section describes the different methods for programming the Atmel

®

ATtiny25/45/85 memories.

20.1

Program And Data Memory Lock Bits

The ATtiny25/45/85 provides two lock bits which can be left unprogrammed (“1”) or can be programmed (“0”) to obtain the additional security listed in

Table 20-2 . The lock bits can only be erased to “1” with the chip erase command.

Program memory can be read out via the debugWIRE interface when the DWEN fuse is programmed, even if the lock bits are set. Thus, when lock bit security is required, should always debugWIRE be disabled by clearing the DWEN fuse.

Table 20-1. Lock Bit Byte

(1)

Lock Bit Byte Bit No

7

6

5

Description

4

3

LB2

2

1

Lock bit

LB1 0 Lock bit

Note: 1.

“1” means unprogrammed, “0” means programmed

Default Value

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

Table 20-2. Lock Bit Protection Modes

(1)(2)

LB Mode

1

Memory Lock Bits

LB2

1

LB1

1

Protection Type

No memory lock features enabled.

2 1 0

Further programming of the flash and EEPROM is disabled in high-voltage and serial programming mode. The fuse bits are locked in both serial and high-voltage programming mode

(1)

. debugWire is disabled.

3 0 0

Further programming and verification of the flash and EEPROM is disabled in high-voltage and serial programming mode. The fuse bits are locked in both serial and high-voltage programming mode

(1)

. debugWire is disabled.

Notes: 1.

Program the fuse bits before programming the LB1 and LB2.

2.

“1” means unprogrammed, “0” means programmed

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20.2

Fuse Bytes

The Atmel

®

ATtiny25/45/85 has three fuse bytes. Table 20-4

,

Table 20-5 and

Table 20-6 on page 126

describe briefly the functionality of all the fuses and how they are mapped into the fuse bytes. Note that the fuses are read as logical zero, “0”, if they are programmed.

Table 20-3. Fuse Extended Byte

Fuse High Byte

SELFPRGEN

2

1

4

3

0

Bit No

7

6

5

Description

-

-

-

-

-

-

-

Self-programming enable

Default Value

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

1 (unprogrammed)

Table 20-4. Fuse High Byte

Fuse High Byte

RSTDISBL

(1)

DWEN

(2)

SPIEN

(3)

WDTON

(4)

Bit No

7

6

5

4

Description

External reset disable

DebugWIRE enable

Enable serial program and data downloading

Watchdog timer always on

Default Value

1 (unprogrammed)

1 (unprogrammed)

0 (programmed, SPI prog. enabled)

1 (unprogrammed)

EESAVE 3

EEPROM memory is preserved through the chip erase

1 (unprogrammed, EEPROM not preserved)

BODLEVEL2

(5)

BODLEVEL1

(5)

2

1

Brown-out detector trigger level

Brown-out detector trigger level

1 (unprogrammed)

1 (unprogrammed)

BODLEVEL0

(5)

0 Brown-out detector trigger level 1 (unprogrammed)

Notes: 1.

See

Section 9.3.2 “Alternate Functions of Port B” on page 50 for description of RSTDISBL and DWEN fuses.

2.

DWEN must be unprogrammed when lock bit security is required.

See

Section 20.1 “Program And Data Memory Lock Bits” on page 123

3.

The SPIEN fuse is not accessible in SPI programming mode.

4.

See

Section 7.9.1 “Watchdog Timer Control Register – WDTCR” on page 38

for details.

5.

See

Table 7-2 on page 35

for BODLEVEL fuse decoding.

6.

When programming the RSTDISBL fuse, high-voltage serial programming has to be used to change fuses to perform further programming.

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Table 20-5. Fuse Low Byte

Fuse Low Byte

CKDIV8

(1)

CKOUT

(2)

Bit No

7

Description

Divide clock by 8

Default Value

0 (unprogrammed)

SUT1

SUT0

CKSEL3

6

5

4

3

Clock output enable

Select start-up time

Select start-up time

Select clock source

1 (unprogrammed)

1 (unprogrammed)

(3)

0 (programmed)

(3)

0 (programmed)

(4)

CKSEL2

CKSEL1

2

1

Select clock source

Select clock source

0 (programmed)

(4)

1 (unprogrammed)

(4)

0 (programmed)

(4)

CKSEL0 0 Select clock source

Notes: 1.

See

Section 5.10 “System Clock Prescaler” on page 26

for details.

2.

The CKOUT fuse allows the system clock to be output on PORTB4.

See “ Section 5.9 “Clock Output Buffer” on page 26 for details.

3.

The default value of SUT1..0 results in maximum start-up time for the default clock source.

See

Table 5-7 on page 23

for details.

4.

The default setting of CKSEL1..0 results in internal RC oscillator at 8.0MHz. See Table 5-6 on page 23 for

details.

The status of the fuse bits is not affected by chip erase. Note that the fuse bits are locked if lock bit1 (LB1) is programmed. program the fuse bits before programming the lock bits.

20.2.1 Latching of Fuses

The fuse values are latched when the device enters programming mode and changes of the fuse values will have no effect until the part leaves programming mode. This does not apply to the EESAVE fuse which will take effect once it is programmed. The fuses are also latched on power-up in normal mode.

20.3

Signature Bytes

All Atmel

®

microcontrollers have a three-byte signature code which identifies the device. This code can be read in both serial and high-voltage programming mode, also when the device is locked. The three bytes reside in a separate address space.

20.3.1 ATtiny25 Signature Bytes

1.

0x000: 0x1E (indicates manufactured by Atmel).

2.

0x001: 0x91 (indicates 2KB flash memory).

3.

0x002: 0x08 (indicates ATtiny25 device when 0x001 is 0x91).

20.3.2 ATtiny45 Signature Bytes

1.

0x000: 0x1E (indicates manufactured by Atmel).

2.

0x001: 0x92 (indicates 4KB flash memory).

3.

0x002: 0x06 (indicates ATtiny45 device when 0x001 is 0x92).

20.3.3 ATtiny85 Signature Bytes

1.

0x000: 0x1E (indicates manufactured by Atmel).

2.

0x001: 0x93 (indicates 8KB flash memory).

3.

0x002: 0x0B (indicates ATtiny85 device when 0x001 is 0x93).

20.4

Calibration Byte

Signature area of the Atmel ATtiny25/45/85 has one byte of calibration data for the internal RC oscillator. This byte resides in the high byte of address 0x000. During reset, this byte is automatically written into the OSCCAL register to ensure correct frequency of the calibrated RC oscillator.

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20.5

Page Size

Table 20-6. No. of Words in a Page and No. of Pages in the Flash

Device

ATtiny25

ATtiny45

ATtiny85

Flash Size

1Kwords

(2Kbytes)

2Kwords

(4Kbytes)

4Kwords

(8Kbytes)

Page Size

16 words

32 words

32 words

PCWORD

PC[3:0]

PC[4:0]

PC[4:0]

No. of Pages

64

64

128

PCPAGE

PC[9:4]

PC[10:5]

PC[11:5]

PCMSB

9

10

11

Table 20-7. No. of Words in a Page and No. of Pages in the EEPROM

Device

ATtiny25

ATtiny45

ATtiny85

EEPROM Size

128 bytes

256 bytes

512 bytes

Page Size

4 bytes

4 bytes

4 bytes

PCWORD

EEA[1:0]

EEA[1:0]

EEA[1:0]

No. of Pages

32

64

128

PCPAGE

EEA[6:2]

EEA[7:2]

EEA[8:2]

EEAMSB

6

7

8

20.6

Serial Downloading

Both the flash and EEPROM memory arrays can be programmed using the serial SPI bus while RESET is pulled to GND.

The serial interface consists of pins SCK, MOSI (input) and MISO (output). After RESET is set low, the programming enable

instruction needs to be executed first before program/erase operations can be executed. NOTE, in Table 20-8 on page 126

, the pin mapping for SPI programming is listed. Not all parts use the SPI pins dedicated for the internal SPI interface.

Figure 20-1. Serial Programming and Verify

(1)

+4.5V to 5.5V

VCC

MOSI

MISO

SCK

RESET

GND

Note: 1.

If the device is clocked by the internal oscillator, it is no need to connect a clock source to the CLKI pin.

Table 20-8. Pin Mapping Serial Programming

Symbol

MOSI

MISO

SCK

Pins

PB0

PB1

PB2

I/O

I

O

I

Description

Serial data in

Serial data out

Serial clock

126 ATtiny25/45/85 Automotive [DATASHEET]

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When programming the EEPROM, an auto-erase cycle is built into the self-timed programming operation (in the serial mode

ONLY) and there is no need to first execute the chip erase instruction. The chip erase operation turns the content of every memory location in both the program and EEPROM arrays into 0xFF.

Depending on CKSEL fuses, a valid clock must be present. The minimum low and high periods for the serial clock (SCK) input are defined as follows:

Low: > 2CPU clock cycles for f ck

< 12MHz, 3CPU clock cycles for f ck

≥ 12MHz

High: > 2CPU clock cycles for f ck

< 12MHz, 3CPU clock cycles for f ck

≥ 12MHz

20.6.1 Serial Programming Algorithm

When writing serial data to the Atmel

®

ATtiny25/45/85, data is clocked on the rising edge of SCK.

When reading data from the Atmel ATtiny25/45/85, data is clocked on the falling edge of SCK. See

Figure 20-2 on page 128

and Figure 20-3 on page 129 for timing details.

To program and verify the ATtiny25/45/85 in the serial programming mode, the following sequence is recommended (see

four byte instruction formats in Table 20-10 on page 128

):

1.

Power-up sequence:

Apply power between V

CC

and GND while RESET and SCK are set to “0”. In some systems, the programmer can not guarantee that SCK is held low during power-up. In this case, RESET must be given a positive pulse of at least two CPU clock cycles duration after SCK has been set to “0”.

2.

Wait for at least 20ms and enable serial programming by sending the programming enable serial instruction to pin

MOSI.

3.

The serial programming instructions will not work if the communication is out of synchronization. When in sync. the second byte (0x53), will echo back when issuing the third byte of the programming enable instruction. Whether the echo is correct or not, all four bytes of the instruction must be transmitted. If the 0x53 did not echo back, give

RESET a positive pulse and issue a new programming enable command.

4.

The flash is programmed one page at a time. The memory page is loaded one byte at a time by supplying the 5

LSB of the address and data together with the load program memory page instruction. To ensure correct loading of the page, the data low byte must be loaded before data high byte is applied for a given address. The program memory page is stored by loading the write program memory page instruction with the 6 MSB of the address. If polling (RDY/BSY) is not used, the user must wait at least t

WD_FLASH

before issuing the next page.

(See

Table 20-9 on page 128

.) Accessing the serial programming interface before the flash write operation completes can result in incorrect programming.

5.

A: The EEPROM array is programmed one byte at a time by supplying the address and data together with the appropriate Write instruction. An EEPROM memory location is first automatically erased before new data is written. If polling (RDY/BSY) is not used, the user must wait at least t

WD_EEPROM before issuing the next byte. (See

Table 20-9 on page 128 .) In a chip erased device, no 0xFFs in the data file(s) need to be programmed.

B: The EEPROM array is programmed one page at a time. The memory page is loaded one byte at a time by supplying the 2 LSB of the address and data together with the Load EEPROM memory page instruction. The

EEPROM memory page is stored by loading the write EEPROM memory page Instruction with the 6 MSB of the address. When using EEPROM page access only byte locations loaded with the Load EEPROM memory page instruction is altered. The remaining locations remain unchanged. If polling (RDY/BSY) is not used, the used must wait at least t

WD_EEPROM

before issuing the next page (See

Table 20-7 on page 126

). In a chip erased device, no

0xFF in the data file(s) need to be programmed.

6.

Any memory location can be verified by using the read instruction which returns the content at the selected address at serial output MISO.

7.

At the end of the programming session, RESET can be set high to commence normal operation.

8.

Power-off sequence (if needed):

Set RESET to “1”.

Turn V

CC

power off.

ATtiny25/45/85 Automotive [DATASHEET]

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Table 20-9. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location

Symbol

t

WD_FLASH t

WD_EEPROM t

WD_ERASE t

WD_FUSE

Minimum Wait Delay

4.5ms

4.0ms

4.0ms

4.5ms

Figure 20-2. Serial Programming Waveforms

Serial Data Input

(MOSI)

MSB LSB

Serial Data Output

(MISO)

Serial Clock Input

(SCK)

Sample

MSB LSB

Table 20-10. Serial Programming Instruction Set

Instruction

Programming enable

Chip erase

Read program memory

Byte 1

1010 1100

1010 1100

0010 H000

Load program memory page 0100 H000

Instruction Format

Byte 2

0101 0011

100x xxxx

0000 000a

000x xxxx

Byte 3

xxxx xxxx xxxx xxxx

bbbb bbbb oooo oooo

xxxb bbbb

Byte4

xxxx xxxx

Operation

Enable serial programming after

RESET goes low.

xxxx xxxx Chip erase EEPROM and flash.

iiii iiii

Read H (high or low) data o from program memory at word address

a:b.

Write H (high or low) data i to program memory page at word address b. Data low byte must be loaded before data high byte is applied within the same address.

Write program memory page 0100 1100

Read EEPROM memory 1010 0000

0000 000a

000x xxxx

bbxx xxxx xxbb bbbb xxxx xxxx

oooo oooo

Write Program memory page at address a:b.

Read data o from EEPROM memory at address b.

Write EEPROM memory 1100 0000 000x xxxx xxbb bbbb

iiii iiii

Write data i to EEPROM memory at address b.

Load EEPROM memory page (Page access)

1100 0001 0000 0000 0000 00bb

iiii iiii

Load data i to EEPROM memory page buffer. After data is loaded, program EEPROM page.

Write EEPROM memory

Page (page access)

1100 0010 00xx xxxx xxbb bb00 xxxx xxxx Write EEPROM page at address b.

Read lock bits

Note:

0101 1000 0000 0000 xxxx xxxx xxoo oooo

Read Lock bits. “0” = programmed,

“1” = unprogrammed. See

Table 20-1 on page 123

for details.

a = address high bits, b = address low bits, H = 0 – Low byte, 1 – high byte, o = data out, i = data in, x = don’t care

128 ATtiny25/45/85 Automotive [DATASHEET]

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Table 20-10. Serial Programming Instruction Set (Continued)

Instruction

Write lock bits

Read signature byte

Write fuse bits

Byte 1

1010 1100

Instruction Format

Byte 2

111x xxxx

Byte 3

xxxx xxxx

Byte4

11ii iiii

Operation

Write lock bits. Set bits = “0” to program lock bits. See

Table 20-1 on page 123 for details.

0011 0000 000x xxxx xxxx xxbb oooo oooo Read signature byte o at address b.

1010 1100 1010 0000 xxxx xxxx

iiii iiii

Set bits = “0” to program, “1” to unprogram. See

Table 20-5 on page

125 for details.

Write fuse high bits

Write extended fuse bits

1010 1100

1010 1100

1010 1000

1010 0100 xxxx xxxx xxxx xxxx

iiii iiii xxxx xxxi

Set bits = “0” to program, “1” to unprogram. See

Table 20-4 on page

124 for details.

Set bits = “0” to program, “1” to unprogram. See

Table 20-3 on page

124 for details.

Read fuse bits

Read fuse high bits

Read extended fuse bits

0101 0000

0101 1000

0000 0000

0000 1000 xxxx xxxx xxxx xxxx

oooo oooo oooo oooo

Read fuse bits. “0” = programmed,

“1” = unprogrammed. See

Table 20-5 on page 125

for details.

Read fuse high bits.

“0” = pro-grammed,

“1” = unprogrammed. See

Table 20-4 on page 124

for details.

0101 0000 0000 1000 xxxx xxxx

oooo oooo

Read extended fuse bits.

“0” = pro-grammed,

“1” = unprogrammed. See

Table 20-3 on page 124

for details.

0011 1000 000x xxxx 0000 0000 oooo oooo Read calibration byte Read calibration byte

Poll RDY/BSY

Note:

1111 0000 0000 0000 xxxx xxxx xxxx xxxo

If o = “1”, a programming operation is still busy. Wait until this bit returns to

“0” before applying another command.

a = address high bits, b = address low bits, H = 0 – Low byte, 1 – high byte, o = data out, i = data in, x = don’t care

20.6.2 Serial Programming Characteristics

Figure 20-3. Serial Programming Timing

MOSI

SCK t

OVSH t

SHOX t

SHSL t

SLSH

MISO t

SLIV

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Table 20-11. Serial Programming Characteristics, T

A

= –40°C to 125°C, V

CC

= 2.7 to 5.5V (Unless Otherwise Noted)

Parameter

Oscillator frequency (ATtiny25/45/85V)

Oscillator period (ATtiny25/45/85V)

Oscillator frequency (ATtiny25/45/85L, VCC = 2.7 to 5.5V)

Oscillator period (ATtiny25/45/85L, VCC = 2.7 to 5.5V)

Oscillator frequency (ATtiny25/45/85, V

CC

= 4.5V to 5.5V)

Oscillator period (ATtiny25/45/85, V

CC

= 4.5V to 5.5V)

SCK pulse width high

SCK pulse width low

MOSI setup to SCK high

MOSI hold after SCK high

Note: 2 t

CLCL

for f ck

< 12MHz, 3 t

CLCL

for f ck

≥12MHz

Symbol

1/t

CLCL t

CLCL

1/t

CLCL t

CLCL

1/t

CLCL t

CLCL t

SHSL t

SLSH t

OVSH t

SHOX

Min

0

250

0

100

0

50

2 t

CLCL*

2 t

CLCL* t

CLCL

2 t

CLCL

Typ Max

4

10

20

Units

MHz ns

MHz ns

MHz ns ns ns ns ns

20.7

High-voltage Serial Programming

This section describes how to program and verify flash program memory, EEPROM data memory, lock bits and fuse bits in the Atmel

®

ATtiny25/45/85.

Figure 20-4. High-voltage Serial Programming

SDI (PB0), SII (PB1)

SCI (PB3) t

IVSH t

SHIX t

SHSL t

SLSH

SDO (PB2) t

SHOV

Table 20-12. Pin Name Mapping

Signal Name in High-voltage Serial

Programming Mode

SDI

SII

SDO

SCI

Pin Name

PB0

PB1

PB2

PB3

I/O

I

I

O

I

Function

Serial data input

Serial instruction input

Serial data output

Serial clock input (min. 220ns period)

130 ATtiny25/45/85 Automotive [DATASHEET]

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Table 20-13. High-voltage Serial Programming Characteristics T

A noted)

= 25°C ±10%, V

CC

= 5.0V ±10% (Unless otherwise

Typ Max Parameter

SCI (PB3) pulse width high

SCI (PB3) pulse width low

SDI (PB0), SII (PB1) Valid to SCI (PB3) high

SDI (PB0), SII (PB1) hold after SCI (PB3) high

SCI (PB3) high to SDO (PB2) valid

Wait after Instr. 3 for write fuse bits

Symbol

t

SHSL t

SLSH t

IVSH t

SHIX t

SHOV t

WLWH_PFB

Min

125

125

50

50

16

2.5

Units

ns ns ns ns ns ms

Table 20-14. Pin Values Used to Enter Programming Mode

Pin

SDI

SII

SDO

Symbol

Prog_enable[0]

Prog_enable[1]

Prog_enable[2]

Value

0

0

0

20.8

High-voltage Serial Programming Algorithm Sequence

To program and verify the Atmel

®

ATtiny25/45/85 in the high-voltage serial programming mode, the following sequence is

recommended (See instruction formats in Table 20-16 ):

20.8.1 Enter High-voltage Serial Programming Mode

The following algorithm puts the device in high-voltage serial programming mode:

1.

Apply 4.5 to 5.5V between V

CC

and GND.

2.

Set RESET pin to “0” and toggle SCI at least six times.

3.

Set the prog_enable pins listed in

Table 20-14 to “000” and wait at least 100ns.

4.

Apply V

HVRST

– 5.5V to RESET. Keep the prog_enable pins unchanged for at least t has been applied to ensure the prog_enable signature has been latched.

HVRST

after the high-voltage

5.

Shortly after latching the prog_enable signature, the device will actively output data on the prog_enable[2]/SDO pin, and the resulting drive contention may increase the power consumption. To minimize this drive contention, release the prog_enable[2] pin after t

HVRST

has elapsed.

6.

Wait at least 50µs before giving any serial instructions on SDI/SII.

Table 20-15. High-voltage Reset Characteristics

Supply Voltage

V

CC

4.5V

5.5V

RESET Pin High-voltage Threshold

V

HVRST

11.5V

11.5V

Minimum High-voltage Period for Latching

Prog_enable

t

HVRST

100ns

100ns

20.8.2 Considerations for Efficient Programming

The loaded command and address are retained in the device during programming. For efficient programming, the following should be considered.

The command needs only be loaded once when writing or reading multiple memory locations.

Skip writing the data value 0xFF that is the contents of the entire EEPROM (unless the EESAVE fuse is programmed) and flash after a chip erase.

Address high byte needs only be loaded before programming or reading a new 256 word window in flash or 256 byte

EEPROM. This consideration also applies to signature bytes reading.

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131

20.8.3 Chip Erase

The chip erase will erase the flash and EEPROM

(1)

memories plus lock bits. The lock bits are not reset until the program memory has been completely erased. The fuse bits are not changed. A chip erase must be performed before the flash and/or EEPROM are re-programmed.

Note: 1.

The EEPROM memory is preserved during chip erase if the EESAVE fuse is programmed.

1.

Load command “chip erase” (see

Table 20-16 on page 134 ).

2.

Wait after instr. 3 until SDO goes high for the “chip erase” cycle to finish.

3.

Load command “no operation”.

20.8.4 Programming the Flash

The flash is organized in pages, see

Table 20-10 on page 128

. When programming the flash, the program data is latched into a page buffer. This allows one page of program data to be programmed simultaneously. The following procedure describes how to program the entire flash memory:

1.

Load command “write flash” (see

Table 20-16 on page 134

).

2.

Load flash page buffer.

3.

Load flash high address and program page. Wait after instr. 3 until SDO goes high for the “page programming” cycle to finish.

4.

Repeat 2 through 3 until the entire flash is programmed or until all data has been programmed.

5.

End page programming by loading command “no operation”.

When writing or reading serial data to the Atmel

®

ATtiny25/45/85, data is clocked on the rising edge of the serial clock, see

Figure 20-6 on page 133

,

Figure 20-7 on page 136 and Figure 20-17 on page 136

for details.

Figure 20-5. Addressing the Flash which is Organized in Pages

Program

Counter

PCMSB

PCPAGE

Page Address within the Flash

PAGEMSB

PCWORD

Word Address within a Page

Program Memory

Page

Page

Instruction Word

PCWORD[PAGEMSB:0]

00

01

02

PAGEEND

132 ATtiny25/45/85 Automotive [DATASHEET]

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Figure 20-6. High-voltage Serial Programming Waveforms

SDI

PB0

MSB

SII

PB1

SDO

PB2

SCI

PB3

0

MSB

MSB

1 2 3 4 5 6 7

LSB

LSB

LSB

8 9 10

20.8.5 Programming the EEPROM

The EEPROM is organized in pages, see

Table 20-11 on page 130

. When programming the EEPROM, the data is latched into a page buffer. This allows one page of data to be programmed simultaneously. The programming algorithm for the

EEPROM data memory is as follows (refer to

Table 20-16 on page 134 ):

1.

Load command “write EEPROM”.

2.

Load EEPROM page buffer.

3.

Program EEPROM page. Wait after instr. 2 until SDO goes high for the “page programming” cycle to finish.

4.

Repeat 2 through 3 until the entire EEPROM is programmed or until all data has been programmed.

5.

End page programming by loading command “no operation”.

20.8.6 Reading the Flash

The algorithm for reading the flash memory is as follows (refer to

Table 20-16 on page 134 ):

1.

Load command “read flash”.

2.

Read flash low and high bytes. The contents at the selected address are available at serial output SDO.

20.8.7 Reading the EEPROM

The algorithm for reading the EEPROM memory is as follows (refer to

Table 20-16 on page 134 ):

1.

Load command “read EEPROM”.

2.

Read EEPROM byte. The contents at the selected address are available at serial output SDO.

20.8.8 Programming and Reading the Fuse and Lock Bits

The algorithms for programming and reading the fuse low/high bits and lock bits are shown in Table 20-16 on page 134 .

20.8.9 Reading the Signature Bytes and Calibration Byte

The algorithms for reading the signature bytes and calibration byte are shown in

Table 20-16 on page 134 .

20.8.10 Power-off sequence

Set SCI to “0”. Set RESET to “1”. Turn V

CC

power off.

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Table 20-16. High-voltage Serial Programming Instruction Set for ATtiny25/45/85

Instruction

Chip erase

Load “write flash” command

SDI

SII

SDO

SDI

SII

SDO

Instr.1/5

0_1000_0000_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0001_0000_00

0_0100_1100_00 x_xxxx_xxxx_xx

Instruction Format

Instr.2/6 Instr.3

0_0000_0000_00

0_0110_0100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

Instr.4

Operation Remarks

Wait after Instr.3 until SDO goes high for the chip erase cycle to finish.

Enter flash programming code.

Load flash page buffer

SDI

SII

SDO

0_ bbbb_bbbb _00

0_0000_1100_00 x_xxxx_xxxx_xx

0_eeee_eeee_00

0_0010_1100_00 x_xxxx_xxxx_xx

0_dddd_dddd_00

0_0011_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_1101_00 x_xxxx_xxxx_xx

Repeat after Instr. 1 - 5 until the entire page buffer is filled or until all data within the page is filled. See note 1.

SDI

SII

SDO

0_0000_0000_00

0_0111_1100_00 x_xxxx_xxxx_xx

Instr 5.

Load flash high address and program page

SDI

SII

SDO

0_0000_000a_00

0_0001_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_0100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

Wait after Instr 3 until SDO goes high. Repeat Instr. 2 - 3 for each loaded flash page until the entire flash or all data is programmed. Repeat

Instr. 1 for a new 256 byte page. See note 1.

Load “read flash” command

Read flash low and high bytes

Load “write

EEPROM” command

SDI

SII

SDO

SDI

SII

SDO

SDI

SII

SDO

SDI

SII

SDO

0_0000_0010_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_bbbb_bbbb_00

0_0000_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_1000_00 x_xxxx_xxxx_xx

0_0001_0001_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0000_000a_00

0_0001_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_1100_00

p_pppp_pppx_xx

0_0000_0000_00

0_0110_1000_00 x_xxxx_xxxx_xx

Enter flash read mode.

0_0000_0000_00

0_0110_1100_00

q_qqqq_qqqx_xx

Repeat Instr. 1, 3 - 6 for each new address. Repeat Instr. 2 for a new 256 byte page.

Instr 5 - 6.

Enter EEPROM programming mode.

Load

EEPROM page buffer

SDI

SII

SDO

0_00bb_bbbb_00

0_0000_1100_00 x_xxxx_xxxx_xx

0_eeee_eeee_00

0_0010_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1101_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

Repeat Instr. 1 - 4 until the entire page buffer is filled or until all data within the page is filled. See note 2.

Program

EEPROM page

Note:

SDI

SII

SDO

0_0000_0000_00

0_0110_0100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

Wait after Instr. 2 until SDO goes high. Repeat Instr. 1 - 2 for each loaded EEPROM page until the entire

EEPROM or all data is programmed.

a = address high bits, b = address low bits, d = data in high bits, e = data in low bits, p = data out high bits,

q = data out low bits,

x = don’t care, 1 = lock Bit1, 2 = lock bit2, 3 = CKSEL0 fuse, 4 = CKSEL1 fuse, 5 = SUT0 fuse, 6 = SUT1 fuse,

7 = CKDIV8, fuse, 8 = WDTON fuse, 9 = EESAVE fuse, A = SPIEN fuse, B = RSTDISBL fuse,

C = BODLEVEL0 fuse, D= BODLEVEL1 fuse, E = MONEN fuse, F = SPMEN fuse

Notes: 1.

For page sizes less than 256 words, parts of the address (bbbb_bbbb) will be parts of the page address.

2.

For page sizes less than 256 bytes, parts of the address (bbbb_bbbb) will be parts of the page address.

3.

The EEPROM is written page-wise. But only the bytes that are loaded into the page are actually written to the

EEPROM. Page-wise EEPROM access is more efficient when multiple bytes are to be written to the same page. Note that auto-erase of EEPROM is not available in high-voltage serial programming, only in SPI programming.

134 ATtiny25/45/85 Automotive [DATASHEET]

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Table 20-16. High-voltage Serial Programming Instruction Set for ATtiny25/45/85 (Continued)

Instruction

Write

EEPROM byte

SDI

SII

SDO

Load “read

EEPROM” command

Read

EEPROM byte

SDI

SII

SDO

Write fuse low bits

SDI

SII

SDO

SDI

SII

SDO

SDI

SII

SDO

Write fuse high bits

Write lock bits

SDI

SII

SDO

SDI

SII

SDO

Read fuse low bits

SDI

SII

SDO

Read fuse high bits

Read lock bits

SDI

SII

SDO

SDI

SII

SDO

Read signature bytes

Read calibration byte

SDI

SII

SDO

SDI

SII

SDO

Instr.1/5

0_00bb_bbbb_00

0_0000_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

0_0000_0011_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_bbbb_bbbb_00

0_0000_1100_00 x_xxxx_xxxx_xx

0_0100_0100_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0100_0000_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0010_0000_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0000_0100_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0000_0100_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0000_0100_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0000_1000_00

0_0100_1100_00 x_xxxx_xxxx_xx

0_0000_1000_00

0_0100_1100_00 x_xxxx_xxxx_xx

Instruction Format

Instr.2/6 Instr.3

0_eeee_eeee_00

0_0010_1100_00 x_xxxx_xxxx_xx

0_aaaa_aaaa_00

0_0001_1100_00 x_xxxx_xxxx_xx

0_A987_6543_00

0_0010_1100_00 x_xxxx_xxxx_xx

0_000F_EDCB_00

0_0010_1100_00 x_xxxx_xxxx_xx

0_0000_0021_00

0_0010_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1000_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_1010_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_1000_00 x_xxxx_xxxx_xx

0_0000_00bb_00

0_0000_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0000_1100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1101_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1000_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_0100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_0100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_0100_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0110_1100_00

A_9876_543x_xx

0_0000_0000_00

0_0111_1110_00 x_xxFE_DCBx_xx

0_0000_0000_00

0_0111_1100_00 x_xxxx_x21x_xx

0_0000_0000_00

0_0110_1000_00 x_xxxx_xxxx_xx

0_0000_0000_00

0_0111_1000_00 x_xxxx_xxxx_xx

Instr.4

0_0000_0000_00

0_0110_0100_00 x_xxxx_xxxx_xx

Operation Remarks

Repeat Instr. 1 - 5 for each new address. Wait after Instr.

5 until SDO goes high. See

Note 3.

Instr. 5

Enter EEPROM read mode.

0_0000_0000_00

0_0110_1100_00

q_qqqq_qqq0_00

Repeat Instr. 1, 3 - 4 for each new address. Repeat Instr. 2 for a new 256 byte page.

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

Wait after Instr. 4 until SDO goes high. Write A - 3 = “0” to program the fuse bit.

0_0000_0000_00

0_0111_1100_00 x_xxxx_xxxx_xx

Wait after Instr. 4 until SDO goes high. Write F - B = “0” to program the fuse bit.

0_0000_0000_00

0_0110_1100_00 x_xxxx_xxxx_xx

Wait after Instr. 4 until SDO goes high. Write 2 - 1 = “0” to program the lock bit.

Reading A - 3 = “0” means the fuse bit is programmed.

Reading F - B = “0” means the fuse bit is programmed.

Reading 2, 1 = “0” means the lock bit is programmed.

0_0000_0000_00

0_0110_1100_00

q_qqqq_qqqx_xx

Repeats Instr 2 4 for each signature byte address.

0_0000_0000_00

0_0111_1100_00

p_pppp_pppx_xx

Load “no operation” command

Note:

SDI

SII

SDO

0_0000_0000_00

0_0100_1100_00 x_xxxx_xxxx_xx

a = address high bits, b = address low bits, d = data in high bits, e = data in low bits, p = data out high bits,

q = data out low bits,

x = don’t care, 1 = lock Bit1, 2 = lock bit2, 3 = CKSEL0 fuse, 4 = CKSEL1 fuse, 5 = SUT0 fuse, 6 = SUT1 fuse,

7 = CKDIV8, fuse, 8 = WDTON fuse, 9 = EESAVE fuse, A = SPIEN fuse, B = RSTDISBL fuse,

C = BODLEVEL0 fuse, D= BODLEVEL1 fuse, E = MONEN fuse, F = SPMEN fuse

Notes: 1.

For page sizes less than 256 words, parts of the address (bbbb_bbbb) will be parts of the page address.

2.

For page sizes less than 256 bytes, parts of the address (bbbb_bbbb) will be parts of the page address.

3.

The EEPROM is written page-wise. But only the bytes that are loaded into the page are actually written to the

EEPROM. Page-wise EEPROM access is more efficient when multiple bytes are to be written to the same page. Note that auto-erase of EEPROM is not available in high-voltage serial programming, only in SPI programming.

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20.9

High-voltage Serial Programming Characteristics

Figure 20-7. High-voltage Serial Programming Timing

V

CC

RESET

1 CK Cycle

WDT

Time-out

RESET

Time-out

Internal

Reset t

TOUT

Table 20-17. High-voltage Serial Programming Characteristics T

A noted)

= 25°C ±10%, V

CC

= 5.0V ±10% (Unless otherwise

Typ Max Parameter

SCI (PB3) pulse width high

SCI (PB3) pulse width low

SDI (PB0), SII (PB1) valid to SCI (PB3) high

SDI (PB0), SII (PB1) hold after SCI (PB3) high

SCI (PB3) high to SDO (PB2) valid

Wait after Instr. 3 for write fuse bits

Symbol

t

SHSL t

SLSH t

IVSH t

SHIX t

SHOV t

WLWH_PFB

Min

110

110

50

50

16

2.5

Units

ns ns ns ns ns ms

136 ATtiny25/45/85 Automotive [DATASHEET]

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21.

Electrical Characteristics

21.1

Absolute Maximum Ratings

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Typ.

Parameters

Operating temperature

Storage temperature

Voltage on any pin except RESET with respect to ground

Voltage on RESET with respect to ground

Maximum operating voltage

DC current per I/O pin

DC current V

CC

and GND pins

Min.

– 40

– 65

– 0.5

– 0.5

6.0

40.0

200.0

Max.

+ 125

+ 150

V

CC

+ 0.5

+ 13.0

Unit

°C

°C

V

V

V mA mA

Table 21-1. DC Characteristics T

A

= – 40°C to 125°C, V

CC

= 2.7V to 5.5V (unless otherwise noted)

(1)

Parameter Condition Symbol Min.

(2)

Typ.

Max.

(3)

Units

Input low voltage

Except RESET and XTAL pins

V

IL

– 0.5

0.3V

CC

V

Input low voltage

Input low voltage

XTAL pin

RESET pin

V

IL1

V

IL2

– 0.5

– 0.5

0.1V

CC

0.1V

CC

V

V

Input high-voltage

Except RESET and XTAL pins

V

IH

0.6V

CC

(3)

V

CC

+ 0.5

Input high-voltage

Input high-voltage

Output low voltage

(4)

(port B) except PB5

Output high-voltage

(5)

(port B) except PB5

Output low voltage

(4)

PB5

I

I

I

XTAL pin

RESET pin

OL

I

OL

I

OH

OH

OL

= 8mA, V

= 1mA

CC

= 5mA, V

CC

= –8mA, V

= –5mA, V

= 5V

= 3V

CC

= 5V

CC

= 3V

V

V

V

V

V

IH1

IH2

OL

OH

OL1

0.9V

CC

(3)

0.9V

CC

(3)

4.1

2.3

Output High-voltage

(5)

PB5

I

OH

= –200µA, V

CC

= 5V V

OH1

3.2

Notes: 1.

All DC characteristics contained in this data sheet result from actual silicon characterization.

2.

“Max” means the highest value where the pin is guaranteed to be read as low.

3.

“Min” means the lowest value where the pin is guaranteed to be read as high.

V

CC

+ 0.5

V

CC

+ 0.5

0.6

0.5

0.6

V

V

V

V

V

V

V

V

V

4.

Although each I/O port can sink more than the test conditions (8mA at V

CC conditions (non-transient), the following must be observed:

= 5V, 5mA at V

CC

= 3V) under steady state

1] The sum of all IOL, for all ports, should not exceed 60mA.

If IOL exceeds the test condition, VOL may exceed the related specification. pins are not guaranteed to sink current greater than the listed test condition.

5.

Although each I/O port can source more than the test conditions (8mA at V

CC state conditions (non-transient), the following must be observed:

= 5V, 5mA at V

CC

= 3V) under steady

1] The sum of all IOH, for all ports, should not exceed 60mA.

If IOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current greater than the listed test condition.

6.

All I/O modules are turned off (PRR = 0xFF) for all I

CC

values.

7.

Brown-out detection (BOD) disabled.

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137

Table 21-1. DC Characteristics T

A

= – 40°C to 125°C, V

CC

= 2.7V to 5.5V (unless otherwise noted)

(1)

(Continued)

Parameter Condition Symbol Min.

(2)

Typ.

Max.

(3)

Units

Input leakage

Current I/O pin except

RESET

Vcc = 5.5V, pin low

(absolute value)

I

IL

50 nA

Input leakage current I/O pin except

RESET

Vcc = 5.5V, pin high

(absolute value)

I

IH

50 nA

Reset pull-up resistor

I/O pin pull-up resistor

R

RST

R pu

30

20

Power supply current

Active 4MHz, V

CC

= 3V

Active 8MHz, V

CC

= 5V

Active 16MHz, V

CC

= 5V

Idle 4MHz, V

CC

= 3V

1.25

5

10

0.4

Idle 8MHz, V

CC

= 5V

Idle 16MHz, V

CC

= 5V

I

CC

(6)

1.2

2.5

Power-down mode

(7)

WDT enabled, V

CC

= 3V

WDT disabled, V

CC

= 3V

5

2

WDT enabled, V

CC

= 5V 9

WDT disabled, V

CC

= 5V 3

Notes: 1.

All DC characteristics contained in this data sheet result from actual silicon characterization.

2.

“Max” means the highest value where the pin is guaranteed to be read as low.

3.

“Min” means the lowest value where the pin is guaranteed to be read as high.

60

50

3

10

15

0.5

2

5

30

24

50

36 k k

Ω

Ω mA mA mA mA mA mA

µA

µA

µA

µA

4.

Although each I/O port can sink more than the test conditions (8mA at V

CC conditions (non-transient), the following must be observed:

= 5V, 5mA at V

CC

= 3V) under steady state

1] The sum of all IOL, for all ports, should not exceed 60mA.

If IOL exceeds the test condition, VOL may exceed the related specification. pins are not guaranteed to sink current greater than the listed test condition.

5.

Although each I/O port can source more than the test conditions (8mA at V

CC state conditions (non-transient), the following must be observed:

= 5V, 5mA at V

CC

= 3V) under steady

1] The sum of all IOH, for all ports, should not exceed 60mA.

If IOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current greater than the listed test condition.

6.

All I/O modules are turned off (PRR = 0xFF) for all I

CC

values.

7.

Brown-out detection (BOD) disabled.

21.2

External Clock Drive Waveforms

Figure 21-1. External Clock Drive Waveforms

t

CHCX t

CHCX t

CLCH t

CHCL

V

IL1

V

IH1 t

CLCX t

CLCL

138 ATtiny25/45/85 Automotive [DATASHEET]

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21.3

External Clock Drive

Table 21-2. External Clock Drive

(1)

Parameter Symbol

V

CC

= 2.7 to 5.5V

Min.

Max.

V

CC

= 4.5 to 5.5V

Min.

Max.

Clock frequency

Clock period

High time

Low time

1/t

CLCL t

CLCL t

CHCX t

CLCX

0

100

40

40

8 0

50

20

20

16

Rise time t

CLCH

1.6

0.5

Fall time t

CHCL

1.6

0.5

Change in period from one clock cycle to the next

Δ

t

CLCL

2

Note: 1.

All DC Characteristics contained in this data sheet result from actual silicon characterization.

2

Figure 21-2. Maximum Frequency versus V

CC

Units

MHz ns ns ns

µs

µs

%

16MHz

8MHz

2.7V

Safe Operating

Area

4.5V

5.5V

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139

21.4

ADC Characteristics – Preliminary Data

Table 21-3. ADC Characteristics, Single Ended Channels. – 40°C to +125°C

(1)

Parameter

Resolution

Condition

Single ended conversion

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 200kHz

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 1MHz

Symbol Min

(1)

Typ

2

3

(1)

Max

10

(1)

Absolute accuracy (Including

INL, DNL, quantization error, gain and offset error)

Integral non-linearity (INL)

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 200kHz noise reduction mode

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 1MHz noise reduction mode

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 200kHz

1.5

2.5

1

Differential non-linearity (DNL)

Gain error

Offset error

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 200kHz

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 200kHz

Single ended conversion

V

REF

= 4V, V

CC

= 4V,

ADC clock = 200kHz

Free running conversion

0.5

2.5

1.5

Conversion time

Clock frequency

Analog supply voltage

Input voltage

Input bandwidth

AVCC

V

IN

V

CC

13

50

– 0.3

(2)

GND

38.5

Internal voltage reference V

INT

1.0

1.1

Analog input resistance R

AIN

100

Notes: 1.

All DC characteristics contained in this data sheet result from actual silicon characterization.

2.

Minimum for AVCC is 2.7V.

3.

Maximum for AVCC is 5.5V.

260

1000

V

CC

+ 0.3

(3)

V

REF

– 50mV

1.2

Units

Bits

LSB

LSB

LSB

LSB

LSB

LSB

LSB

LSB

µs kHz

V

V kHz

V

MW

21.5

Calibrated RC Oscillator Accuracy

Table 21-4. Calibration Accuracy of Internal RC Oscillator

Factory calibration

User calibration

Frequency

8.0MHz

7.3 to 8.1MHz

V

CC

3V

2.7V to 5.5V

Temperature

25°C

–40°C ±125°C

Calibration Accuracy

±1%

±14%

140 ATtiny25/45/85 Automotive [DATASHEET]

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22.

Typical Characteristics

The data contained in this section is extracted from preliminary silicon characterization and will be updated upon final characterization.

The following charts show typical behavior. These figures are not tested during manufacturing. All current consumption measurements are performed with all I/O pins configured as inputs and with internal pull-ups enabled. A sine wave generator with rail to rail output is used as clock source.

The power consumption in power-down mode is independent of clock selection.

The current consumption is a function of several factors such as: operating voltage, operating frequency, loading of I/O pins, switching rate of I/O pins, code executed and ambient temperature. The dominating factors are operating voltage and frequency.

The current drawn from capacitive loaded pins may be estimated (for one pin) as

CL

×

VCC

× f where CL = load capacitance, VCC = operating voltage and f = average switching frequency of I/O pin.

The parts are characterized at frequencies higher than test limits. Parts are not guaranteed to function properly at frequencies higher than the ordering code indicates.

The difference between current consumption in power-down mode with watchdog timer enabled and power-down mode with watchdog timer disabled represents the differential current drawn by the watchdog timer.

22.1

Active Supply Current

Figure 22-1. Active Supply Current versus Frequency (0.1 to 1.0MHz)

0.040

0.035

5.5V

5.0V

4.5V

4.0V

0.030

0.025

0.020

0.015

0.010

0.005

0

0 0.1

0.2

0.3

0.4

0.5

0.6

Frequency (MHz)

0.7

0.8

0.9

1

3.3V

2.7V

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Figure 22-2. Active Supply Current versus Frequency (1 to 20MHz)

14

12

10

8

6

4

2

0

0 2 4 6

2.7V

8 10

Frequency (MHz)

12

3.3V

14

Figure 22-3. Active Supply Current versus V

CC

(Internal RC Oscillator, 128kHz)

0.25

16

4.0V

18 20

5.5V

5.0V

4.5V

0.2

0.15

125°C

85°C

25°C

-40°C

0.1

0.05

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

Figure 22-4. Active Supply Current versus V

CC

(Internal RC Oscillator, 1MHz)

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5

5

5.5

5.5

125°C

85°C

25°C

-40°C

142 ATtiny25/45/85 Automotive [DATASHEET]

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Figure 22-5. Active Supply Current versus V

CC

(Internal RC Oscillator, 8MHz)

8

7

4

3

6

5

2

1

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

22.2

Idle Supply Current

Figure 22-6. Idle Supply Current versus Frequency (0.1 to 1.0MHz)

0.25

0.2

0.15

0.1

0.05

0

0

5

0.1

0.2

0.3

0.4

0.5

0.6

Frequency (MHz)

0.7

0.8

0.9

5.5

125°C

85°C

25°C

-40°C

1

5.5V

5.0V

4.5V

4.0V

3.3V

2.7V

1.8V

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143

Figure 22-7. Idle Supply Current versus Frequency (1 to 20MHz)

4

3.5

1

0.5

0

0

3

2.5

2

1.5

2 4

1.8V

6

2.7V

8 10 12

Frequency (MHz)

3.3V

14

Figure 22-8. Idle Supply Current versus V

CC

(Internal RC Oscillator, 128kHz)

0.25

16

4.0V

18

0.2

20

5.5V

5.0V

4.5V

125°C

85°C

25°C

-40°C

0.15

0.1

0.05

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

Figure 22-9. Idle Supply Current versus V

CC

(Internal RC Oscillator, 1MHz)

0.6

0.5

0.4

0.3

0.2

0.1

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5

5

5.5

5.5

125°C

85°C

25°C

-40°C

144 ATtiny25/45/85 Automotive [DATASHEET]

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Figure 22-10. Idle Supply Current versus V

CC

(Internal RC Oscillator, 8MHz)

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5 5.5

125°C

85°C

25°C

-40°C

22.2.1 Using the Power Reduction Register

The tables and formulas below can be used to calculate the additional current consumption for the different I/O modules in active and idle mode. The enabling or disabling of the I/O modules are controlled by the power reduction register. See

Section 6.6 “Power Reduction Register” on page 30 for details.

Table 22-1. Additional Current Consumption for the different I/O modules (absolute values)

PRR bit

PRTIM1

PRTIM0

PRUSI

PRADC

V

CC

= 2V, F = 1MHz

43µA

5.0µA

4.0µA

13µA

Typical numbers

V

CC

= 3V, F = 4MHz

270µA

28µA

25µA

84µA

V

CC

= 5V, F = 8MHz

1090µA

116µA

102µA

351µA

Table 22-2. Additional Current Consumption (percentage) in Active and Idle mode

PRR bit

PRTIM1

PRTIM0

PRUSI

PRADC

Additional Current consumption compared to

Active with external clock

(see Figure 22-1

and

Figure 22-2

)

Additional Current consumption compared to

Idle with external clock

(see

Figure 22-6

and Figure 22-7

)

17.3% 68.4%

1.8%

1.6%

5.4%

7.3%

6.4%

21.4%

It is possible to calculate the typical current consumption based on the numbers from Table 22-2 for other V

CC settings than listed in

Table 22-1 .

and frequency

ATtiny25/45/85 Automotive [DATASHEET]

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145

22.2.1.1Example 1

Calculate the expected current consumption in idle mode with USI, TIMER0, and ADC enabled at V

CC

= 2.0V and F = 1MHz.

From Table 22-2 on page 145

, third column, we see that we need to add 6.4% for the USI, 7.3% for the TIMER0 module, and

21.4% for the ADC module. Reading from Figure 22-9

, we find that the idle current consumption is ~0.25mA at V

CC and F = 1MHz. The total current consumption in idle mode with USI, TIMER0, and ADC enabled, gives:

= 3.0V

I

CCtotal

(0.25) mA

×

(1 + 0.064 + 0.073 + 0.214)

0.337mA

22.3

Power-Down Supply Current

Figure 22-11. Power-Down Supply Current versus V

CC

(Watchdog Timer Disabled)

4

3.5

3

2.5

2

1.5

1

0.5

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5

125°C

5.5

85°C

-40°C

25°C

Figure 22-12. Power-Down Supply Current versus V

CC

(Watchdog Timer Enabled)

12

10

8

6

4

2

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5 5.5

125°C

-40°C

25°C

85°C

146 ATtiny25/45/85 Automotive [DATASHEET]

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22.4

Pin Pull-up

Figure 22-13. I/O Pin Pull-Up Resistor Current versus Input Voltage (V

CC

= 1.8V)

60

50

40

30

20

10

0

0 0.2

0.4

0.6

0.8

1

V

OP

(V)

1.2

1.4

1.6

Figure 22-14. I/O Pin Pull-Up Resistor Current versus Input Voltage (V

CC

= 2.7V)

90

80

70

60

50

40

30

20

10

0

0 0.5

1 1.5

V

OP

(V)

2 2.5

1.8

2

-40°C

25°C

85°C

125°C

3

125°C

85°C

25°C

-40°C

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147

Figure 22-15. I/O Pin Pull-Up Resistor Current versus Input Voltage (V

CC

= 5.0V)

160

140

120

100

80

60

40

20

0

0 0.5

1 1.5

2 2.5

V

OP

(V)

3 3.5

4 4.5

Figure 22-16. Reset Pull-Up Resistor Current versus Reset Pin Voltage (V

CC

= 1.8V)

40

35

30

25

20

15

10

5

0

0 0.2

0.4

0.6

0.8

1

V

RESET

(V)

1.2

1.4

1.6

1.8

Figure 22-17. Reset Pull-Up Resistor Current versus Reset Pin Voltage (V

CC

= 2.7V)

70

60

50

40

30

20

10

0

0 0.5

1 1.5

V

RESET

(V)

2 2.5

5

125°C

85°C

25°C

-40°C

2

125°C

85°C

25°C

-40°C

3

125°C

85°C

25°C

-40°C

148 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-18. Reset Pull-Up Resistor Current versus Reset Pin Voltage (V

CC

= 5.0V)

140

120

100

80

60

40

20

0

0 1 2 3

V

RESET

(V)

4 5

22.5

Pin Driver Strength

Figure 22-19. I/O Pin Source Current versus Output Voltage (V

CC

= 1.8V)

12

10

8

6

4

2

0

0 0.2

0.4

0.6

0.8

1

V

OL

(V)

1.2

1.4

1.6

1.8

-40°C

25°C

85°C

125°C

6

125°C

85°C

25°C

-40°C

2

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149

Figure 22-20. I/O Pin Source Current versus Output Voltage (V

CC

= 3V)

1.2

1

0.8

0.6

0.4

0.2

0

0 5 10

I

OL

(V)

15 20

125°C

85°C

25°C

-40°C

Figure 22-21. I/O Pin Source Current versus Output Voltage (V

CC

= 5V)

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

0 5 10 15

I

OL

(V)

20

Figure 22-22. I/O Pin Sink Current versus Output Voltage (V

CC

= 1.8V)

9

8

25°C

7

6

5

85°C

125°C

4

3

2

1

0

0 0.2

0.4

0.6

0.8

1

V

OH

(V)

1.2

1.4

-40°C

1.6

125°C

85°C

25°C

-40°C

1.8

25

25

2

150 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-23. I/O Pin Sink Current versus Output Voltage (V

CC

= 3V)

3.5

3

2.5

2

1.5

1

0.5

0

0 5 10

I

OH

(mA)

15

Figure 22-24. I/O Pin Sink Current versus Output Voltage (V

CC

= 5.0V)

5.1

5

4.9

4.8

4.7

4.6

4.5

4.4

4.3

0 5 10 15

I

OH

(mA)

20

-40°C

25°C

85°C

125°C

25

-40°C

20

25°C

85°C

125°C

25

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

151

22.6

Pin Thresholds and Hysteresis

Figure 22-25. I/O Pin Input Threshold Voltage versus V

CC

(VIH, I/O Pin Read As '1')

3

2.5

2

1.5

1

0.5

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

Figure 22-26. I/O Pin Input Threshold Voltage versus V

CC

(VIL, I/O Pin Read As '0')

2.5

5

2

1.5

1

0.5

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5

5.5

5.5

-40°C

25°C

85°C

125°C

125°C

85°C

25°C

-40°C

152 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-27. I/O Pin Input Hysteresis versus V

CC

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

Figure 22-28. Reset Input Threshold Voltage versus V

CC

(VIH, Reset Pin Read As '1')

2.5

5

2

1.5

1

0.5

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

Figure 22-29. Reset Input Threshold Voltage versus V

CC

(VIL, Reset Pin Read As '0')

2.5

5

2

1.5

1

0.5

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5

5.5

5.5

5.5

-40°C

25°C

85°C

125°C

125°C

85°C

25°C

-40°C

125°C

85°C

25°C

-40°C

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

153

Figure 22-30. Reset Input Pin Hysteresis versus V

CC

0.25

0.2

0.15

0.1

0.05

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5 5.5

125°C

85°C

25°C

-40°C

22.7

BOD Thresholds and Analog Comparator Offset

Figure 22-31. BOD Thresholds versus Temperature (BODLEVEL Is 4.3V)

4.4

4.35

4.3

4.25

4.2

4.15

4.1

4.05

Rising

Falling

0

-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Temperature (°C)

154 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-32. BOD Thresholds versus Temperature (BODLEVEL Is 2.7V)

2.8

Rising

2.75

2.7

2.65

2.6

2.55

Falling

0

-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Temperature (°C)

Figure 22-33. BOD Thresholds versus Temperature (BODLEVEL Is 1.8V)

1.9

1.85

1.8

1.75

1.7

1.65

Rising V

CC

Falling V

CC

1.6

-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Temperature (°C)

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

155

22.8

Internal Oscillator Speed

Figure 22-34. Watchdog Oscillator Frequency versus V

CC

)

0.118

0.116

0.114

0.112

0.110

0.108

0.106

0.104

0.102

0.1

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5 5.5

-40°C

25°C

85°C

125°C

Figure 22-35. Watchdog Oscillator Frequency versus Temperature

0.118

0.116

0.114

0.112

0.110

0.108

0.106

0.104

0.102

0.1

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

1.8V

2.7V

3.6V

4.0V

5.5V

156 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-36. Calibrated 8MHz RC Oscillator Frequency versus Temperature

8.4

8

7.9

7.8

7.7

8.3

8.2

8.1

7.6

7.5

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

5.0V

3.0V

Figure 22-37. Calibrated 8MHz RC Oscillator Frequency versus V

CC

8.4

8.3

8.2

8.1

8

7.9

7.8

7.7

7.6

7.5

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5 5.5

125°C

85°C

25°C

-40°C

Figure 22-38. Calibrated 8MHz RC Oscillator Frequency versus OSCCAL Value

14

12

10

8

6

4

2

0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240

OSCCAL (X1)

125°C

85°C

25°C

-40°C

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

157

22.9

Current Consumption of Peripheral Units

Figure 22-39. Brownout Detector Current versus V

CC

35

30

25

20

15

10

5

0

1.5

2 2.5

3 3.5

V

CC

(V)

Figure 22-40. Analog Comparator Current versus V

CC

350

300

250

200

150

100

50

0

1.5

2 2.5

3 3.5

V

CC

(V)

4

4

4.5

4.5

5

5

5.5

5.5

125°C

85°C

25°C

-40°C

150°C

125°C

85°C

25°C

6

-40°C

158 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

22.10 Current Consumption in Reset and Reset Pulse width

Figure 22-41. Reset Supply Current versus V

CC

(0.1 to 1.0MHz, Excluding Current through the Reset Pull-up)

0.14

5.5V

0.12

5.0V

0.1

0.08

4.5V

4.0V

0.06

3.3V

2.7V

0.04

1.8V

0.02

1

0 0.1

0.2

0.3

0.4

0.5

0.6

Frequency (MHz)

0.7

0.8

0.9

1

Figure 22-42. Reset Supply Current versus V

CC

(1 to 24MHz, Excluding Current through the Reset Pull-up)

2.5

5.5V

5.0V

2

4.5V

1.5

4.0V

1

3.3V

0.5

2.7V

0

0 2 4

1.8V

6 8 10 12

Frequency (MHz)

14 16 18 20

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

159

Figure 22-43. Reset Pulse Width versus V

CC

2500

2000

1500

1000

500

5.5

125°C

85°C

25°C

-40°C

0

1.5

2 2.5

3 3.5

V

CC

(V)

4 4.5

5

22.11 Analog to Digital Converter

Figure 22-44. Analog to Digital Converter Differential Mode OFFSET versus V

CC

2

1.5

1

0.5

0

-0.5

-1

-1.5

-2

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

Diff x1

Diff x20

160 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-45. Analog to Digital Converter Single Ended Mode OFFSET versus V

CC

2.5

2

1.5

1

0.5

0

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

Figure 22-46. Analog to Digital Converter Differential Mode GAIN versus V

CC

-1

-1.2

-1.4

-1.6

-1.8

-2

-2.2

-2.4

-2.6

-2.8

-3

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

Diff x20

Diff x1

Figure 22-47. Analog to Digital Converter Single Ended Mode GAIN versus V

CC

0

-40 -30 -20 -10 0 10 20 30 40 50 60 70 80

-0.5

90 100 100 120

-1

-1.5

-2

-2.5

Temperature (°C)

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

161

Figure 22-48. Analog to Digital Converter Differential Mode DNL versus V

CC

1.2

1

0.8

Diff x20

0.6

0.4

0.2

0

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

Diff x1

Figure 22-49. Analog to Digital Converter Single Ended Mode DNL versus V

CC

0.57

0.56

0.55

0.54

0.53

0.52

0.51

0.5

0.49

0.48

0.47

-40 -30 -20 -10 0 10 20 30 40 50 60

Temperature (°C)

70 80 90 100 110 120

Figure 22-50. Analog to Digital Converter Differential Mode INL versus V

CC

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

Diff x20

Diff x1

162 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

Figure 22-51. Analog to Digital Converter Single Ended Mode INL versus V

CC

0.72

0.7

0.68

0.66

0.64

0.62

0.6

0.58

-40 -30 -20 -10 0 10 20 30 40 50

Temperature (°C)

60 70 80 90 100 110 120

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

163

23.

Register Summary

Address

0x3F

0x3E

0x3D

0x3C

0x3B

Name

SREG

SPH

SPL

Reserved

GIMSK

0x3A GIFR

0x39 TIMSK

Bit 7

I

SP7

Bit 6

T

SP6

INT0

Bit 5

H

SP5

PCIE

Bit 4

S

SP4

Bit 3

V

SP3

Bit 2

N

SP2

Bit 1

Z

SP1

INTF0 PCIF – – – –

OCIE1A OCIE1B OCIE0A OCIE0B TOIE1 TOIE0

Bit 0

C

SP8

SP0

0x38 TIFR

0x37 SPMCSR

0x36 Reserved

0x35 MCUCR

OCF1A OCF1B OCF0A OCF0B TOV1

– – CTPB RFLB

TOV0 –

PGWRT PGERS SPMEN

PUD SE SM1 SM0 BODSE ISC01 ISC00 BODS

0x34 MCUSR – –

0x33 TCCR0B FOC0A FOC0B

WDRF

WGM02

BORF

CS02

EXTRF

CS01

PORF

CS00

0x32 TCNT0

0x31 OSCCAL

0x30 TCCR1

0x2F TCNT1

0x2E

0x2D

0x2C

0x2B

OCR1A

OCR1C

GTCCR

OCR1B

CTC1

Timer/Counter0

Oscillator Calibration Register

PWM1A COM1A1 COM1A0 CS13

Timer/Counter1

CS12 CS11

Timer/Counter1 Output Compare Register A

Timer/Counter1 Output Compare Register C

TSM PWM1B COM1B1 COM1B0 FOC1B FOC1A PSR1

Timer/Counter1 Output Compare Register B

CS10

PSR0

0x2A TCCR0A COM0A1 COM0A0 COM0B1 COM0B0

0x29 OCR0A

Timer/Counter0 – Output Compare Register A

WGM01 WGM00

0x28 OCR0B

0x27 PLLCSR SM –

Timer/Counter0 – Output Compare Register B

– – – PCKE PLLE PLOCK

0x26 CLKPR CLKPCE

0x25 DT1A

0x24 DT1B

0x23 DTPS1

– – – CLKPS3 CLKPS2 CLKPS1 CLKPS0

DT1AH3 DT1AH2 DT1AH1 DT1AH0 DT1AL3 DT1AL2 DT1AL1 DT1AL0

DT1BH3 DT1BH2 DT1BH1 DT1BH0 DT1BL3 DT1BL2 DT1BL1 DT1BL0

– – – – – – DTPS11 DTPS10

0x22 DWDR DWDR[7:0]

0x21 WDTCR WDTIF WDTIE WDP3 WDCE WDE

0x20 PRR

0x1F EEARH

– –

WDP2

PRTIM1 PRTIM0

WDP1

PRUSI

WDP0

PRADC

EEAR8

Page

6

9

9

54

55

70

71

121

28

,

49 ,

54

37

69

70

24

77

79

79

79

73 ,

78

80

66

70

70

81

26

87

87

86

118

38

30

14

0x1E

0x1D

EEARL

EEDR

EEAR7 EEAR6 EEAR5 EEAR4 EEAR3

EEPROM Data Register

EEAR2 EEAR1 EEAR0

14

14

0x1C EECR – – EEPM1 EEPM0 EERIE EEMWE EEWE EERE

14

Notes: 1.

For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory addresses should never be written.

2.

I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC instructions.

3.

Some of the Status Flags are cleared by writing a logical one to them. Note that, unlike most other AVRs, the CBI and

SBI instructions will only operation the specified bit, and can therefore be used on registers containing such Status

Flags. The CBI and SBI instructions work with registers 0x00 to 0x1F only.

164 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

23.

Register Summary (Continued)

Address Name

0x1B Reserved

0x1A Reserved

0x19 Reserved

0x18 PORTB

0x17 DDRB

0x16 PINB

0x15 PCMSK

0x14 DIDR0

0x13 GPIOR2

0x12

0x11

GPIOR1

GPIOR0

0x10 USIBR

0x0F USIDR

Bit 7

Bit 6

Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

PORTB5 PORTB4 PORTB3 PORTB2 PORTB1 PORTB0

DDB5 DDB4 DDB3 DDB2 DDB1 DDB0

PINB5 PINB4 PINB3 PINB2 PINB1 PINB0

PCINT5 PCINT4 PCINT3 PCINT2 PCINT1 PCINT0

ADC0D ADC2D ADC3D ADC1D EIN1D AIN0D

General Purpose I/O Register 2

General Purpose I/O Register 1

General Purpose I/O Register 0

USI Buffer Register

Page

100

53

53

53

55

,

116

0x0E USISR

0x0D USICR

0x0C

0x0B

Reserved

Reserved

0x0A

0x09

0x08

0x07

0x06

0x05

0x04

0x03

Reserved

Reserved

ACSR

ADMUX

ADCSRA

ADCH

ADCL

ADCSRB

USICIF

USISIE

ACD

REFS1

ADEN

BIN

USIOIF

USIOIE USIWM1 USIWM0 USICS1 USICS0 USICLK

ACBG

REFS0

ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0

ADC Data Register High Byte

ACME

USIPF

ACO

ADLAR

IPR

USIDC USICNT3 USICNT2 USICNT1 USICNT0

ACI

REFS2

ACIE

MUX3

MUX2

ADC Data Register Low Byte

– – ADTS2

ACIS1 ACIS0

MUX1 MUX0

ADTS1

USITC

ADTS0

98

94

94

95

96

98

112

114

115

115

,

115

0x02

0x01

Reserved

Reserved

0x00 Reserved –

Notes: 1.

For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory addresses should never be written.

2.

I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC instructions.

3.

Some of the Status Flags are cleared by writing a logical one to them. Note that, unlike most other AVRs, the CBI and

SBI instructions will only operation the specified bit, and can therefore be used on registers containing such Status

Flags. The CBI and SBI instructions work with registers 0x00 to 0x1F only.

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

165

24.

Instruction Set Summary

Mnemonics Operands Description

CPI

SBRC

SBRS

SBIC

SBIS

BRBS

BRBC

BREQ

BRNE

BRCS

Rd, K

Rr, b

Rr, b

P, b

P, b s, k s, k

k

k

k

Compare register with immediate

Skip if bit in register cleared

Skip if bit in register is set

Skip if bit in I/O register cleared

Skip if bit in I/O register is set

Branch if status flag set

Branch if status flag cleared

Branch if equal

Branch if not equal

Branch if carry set

Operation

Arithmetic and Logic Instructions

ADD

ADC

ADIW

SUB

SUBI

SBC

SBCI

SBIW

AND

ANDI

OR

ORI

EOR

COM

NEG

SBR

CBR

INC

DEC

TST

CLR

SER

Rd, Rr

Rd, Rr

Rdl, K

Rd, Rr

Add two registers

Add with carry two registers

Add immediate to word

Subtract two registers

Rd

Rd + Rr

Rd

Rd + Rr + C

Rdh: Rdl

Rdh: Rdl + K

Rd

Rd – Rr

Rd, K

Rd, Rr

Subtract constant from register

Subtract with carry two registers

Rd

Rd – K

Rd

Rd – Rr – C

Rd, K Subtract with carry constant from Reg. Rd

Rd – K – C

Rdl, K Subtract immediate from word Rdh:Rdl

Rdh:Rdl – K

Rd, Rr

Rd, K

Rd, Rr

Rd, K

Rd, Rr

Rd

Rd

Rd, K

Rd, K

Rd

Rd

Rd

Rd

Rd

Logical AND registers

Logical AND register and constant

Logical OR registers

Logical OR register and constant

Exclusive OR registers

One’s complement

Two’s complement

Set Bit(s) in register

Clear Bit(s) in register

Increment

Decrement

Test for zero or minus

Clear register

Set register

Rd

Rd

×

Rr

Rd

Rd

×

K

Rd

Rd v Rr

Rd

Rd v K

Rd

Rd

Rr

Rd

0xFF – Rd

Rd

0x00 – Rd

Rd

Rd v K

Rd

Rd

×

(0xFF – K)

Rd

Rd + 1

Rd

Rd – 1

Rd

Rd

×

Rd

Rd

Rd

Rd

Rd

0xFF

Branch Instructions

RJMP

IJMP

RCALL

ICALL

RET

RETI

CPSE k k

Rd, Rr

Relative jump

Indirect jump to (Z)

Relative subroutine call

Indirect call to (Z)

Subroutine return

Interrupt return

Compare, skip if equal

PC

PC + k + 1

PC

Z

PC

PC + k + 1

PC

Z

PC

STACK

PC

STACK if (Rd = Rr) PC

PC + 2 or 3

CP

CPC

Rd, Rr Compare

Rd, Rr Compare with carry

Rd – Rr

Rd – Rr – C

Rd – K if (Rr(b)=0) PC

PC + 2 or 3 if (Rr(b)=1) PC

PC + 2 or 3 if (P(b)=0) PC

PC + 2 or 3 if (P(b)=1) PC

PC + 2 or 3 if (SREG (s) = 1) then PC

PC + k + 1 if (SREG (s) = 0) then PC

PC + k + 1 if (Z = 1) then PC

PC + k + 1 if (Z = 0) then PC

PC + k + 1 if (C = 1) then PC

PC + k + 1

Flags #Clocks

4

4

1/2/3

1

1

3

3

2

2

1

1/2/3

1/2/3

1/2/3

1/2/3

1/2

1/2

1/2

1/2

1/2

None

None

None

None

None

I

None

Z, N,V,C,H

Z, N,V,C,H

Z, N,V,C,H

None

None

None

None

None

None

None

None

None

Z,C,N,V,H

Z,C,N,V,H

Z,C,N,V,S

Z,C,N,V,H

Z,C,N,V,H

Z,C,N,V,H

Z,C,N,V,H

Z,C,N,V,S

Z,N,V

Z,N,V

Z,N,V

Z,N,V

Z,N,V

Z,C,N,V

Z,C,N,V,H

Z,N,V

Z,N,V

Z,N,V

Z,N,V

Z,N,V

Z,N,V

None

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

2

1

1

2

1

1

1

166 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

24.

Instruction Set Summary (Continued)

CLZ

SEI

CLI

SES

CLS

SEV

CLV

SET

CLT

SEH

Mnemonics Operands Description

BRCC k Branch if carry cleared

BRSH

BRLO

BRMI

BRPL

k

k

k

k

Branch if same or higher

Branch if lower

Branch if minus

Branch if plus

BRGE

BRLT

BRHS

BRHC

BRTS

BRTC

BRVS

BRVC

k

k

k

k

k

k

k

k

Branch if greater or equal, signed

Branch if less than zero, signed

Branch if half carry flag set

Branch if half carry flag cleared

Branch if T flag set

Branch if T flag cleared

Branch if overflow flag is set

Branch if overflow flag is cleared

SWAP

BSET

BCLR

BST

BLD

SEC

CLC

SEN

CLN

SEZ

BRIE

BRID

k

k

Branch if interrupt enabled

Branch if interrupt disabled

Bit and bit-test instructions

SBI P,b Set bit in I/O register

CBI

LSL

LSR

ROL

ROR

ASR

P,b

Rd

Rd

Rd

Rd

Rd

Clear bit in I/O register

Logical shift left

Logical shift right

Rotate left through carry

Rotate right through carry

Arithmetic shift right

Rd s s

Rr, b

Rd, b

Swap nibbles

Flag set

Flag clear

Bit Store from register to T

Bit load from T to register

Set carry

Clear carry

Set negative flag

Clear negative flag

Set zero flag

Clear zero flag

Global interrupt enable

Global interrupt disable

Set signed test flag

Clear signed test flag

Set twos complement overflow.

Clear twos complement overflow

Set T in SREG

Clear T in SREG

Set half carry flag in SREG

Operation

if (C = 0) then PC

PC + k + 1 if (C = 0) then PC

PC + k + 1 if (C = 1) then PC

PC + k + 1 if (N = 1) then PC

PC + k + 1 if (N = 0) then PC

PC + k + 1 if (N

V= 0) then PC

PC + k + 1 if (N

V= 1) then PC

PC + k + 1 if (H = 1) then PC

PC + k + 1 if (H = 0) then PC

PC + k + 1 if (T = 1) then PC

PC + k + 1 if (T = 0) then PC

PC + k + 1 if (V = 1) then PC

PC + k + 1 if (V = 0) then PC

PC + k + 1 if (I = 1) then PC

PC + k + 1 if (I = 0) then PC

PC + k + 1

Z

0

I

1

I

0

S

1

S

0

V

1

V

0

T

1

T

0

H

1

I/O (P, b)

1

I/O (P, b)

0

Rd(n+1)

Rd (n), Rd(0)

0

None

None

Z,C,N,V

Rd(n)

Rd(n+1), Rd(7)

0 Z,C,N,V

Rd(0)

C,Rd(n+1)

Rd (n), C

Rd(7) Z,C,N,V

Rd(7)

C, Rd (n)

Rd(n+1),C

Rd(0) Z,C,N,V

Rd(n)

Rd(n+1), n=0..6

Z,C,N,V

Rd(3.0)

Rd(7..4),Rd(7..4)

Rd(3..0)

SREG(s)

1

SREG(s)

0

T

Rr(b)

Rd(b)

T

C

1

C

0

N

1

N

0

Z

1

None

SREG(s)

SREG(s)

T

None

C

C

N

N

Z

Z

I

I

S

S

V

V

T

T

H

None

None

None

None

None

None

None

None

None

None

Flags

None

None

None

None

None

1/2

1/2

1/2

1/2

1/2

1/2

1/2

1/2

1/2

1/2

#Clocks

1/2

1/2

1/2

1/2

1/2

1

1

1

1

1

1

1

1

1

1

1

1

2

2

1

1

1

1

1

1

1

1

1

1

1

1

1

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

167

24.

Instruction Set Summary (Continued)

STD

ST

ST

ST

STD

STS

LPM

LPM

LPM

SPM

ST

ST

ST

ST

ST

ST

LD

LD

LDD

LDS

Mnemonics Operands Description

CLH Clear half carry flag in SREG

Data transfer instructions

MOV Rd, Rr Move between registers

MOVW

LDI

Rd, Rr

Rd, K

Copy register word

Load immediate

LD

LD

LDD

LD

LD

LD

LD

LD

Rd, X

Rd, X+

Rd, - X

Rd, Y

Rd, Y+

Rd, - Y

Rd,Y+q

Rd, Z

Load indirect

Load indirect and post-inc.

Load indirect and pre-dec.

Load indirect

Load indirect and post-inc.

Load indirect and pre-dec.

Load indirect with displacement

Load indirect

Rd, Z+

Rd, -Z

Rd, Z+q

Rd, k

X, Rr

Load indirect and post-inc.

Load indirect and pre-dec.

Load indirect with displacement

Load direct from SRAM

Store indirect

X+, Rr Store indirect and post-inc.

- X, Rr Store indirect and pre-dec.

Y, Rr Store indirect

Y+, Rr Store indirect and post-inc.

- Y, Rr Store indirect and pre-dec.

Y+q,Rr Store indirect with displacement

Z, Rr Store indirect

Z+, Rr Store indirect and post-inc.

-Z, Rr Store indirect and pre-dec.

Z+q,Rr Store indirect with displacement k, Rr Store direct to SRAM

Load program memory

Rd, Z Load program memory

Rd, Z+ Load program memory and post-inc

Store program memory

IN

OUT

PUSH

POP

Rd, P In port

P, Rr Out port

Rr

Rd

Push register on stack

Pop register from stack

MCU Control Instructions

NOP No operation

SLEEP

WDR

BREAK

Sleep

Watchdog reset

Break

Operation

H

0

Rd

Rr

Rd+1:Rd

Rr+1:Rr

Rd

K

Rd

(X)

Rd

(X), X

X + 1

X

X – 1, Rd

(X)

Rd

(Y)

Rd

(Y), Y

Y + 1

Y

Y – 1, Rd

(Y)

Rd

(Y + q)

Rd

(Z)

Rd

(Z), Z

Z+1

Z

Z – 1, Rd

(Z)

Rd

(Z + q)

Rd

(k)

(X)

Rr

(X)

Rr, X

X + 1

X

X – 1, (X)

Rr

(Y)

Rr

(Y)

Rr, Y

Y + 1

Y

Y – 1, (Y)

Rr

(Y + q)

Rr

(Z)

Rr

(Z)

Rr, Z

Z + 1

Z

Z – 1, (Z)

Rr

(Z + q)

Rr

(k)

Rr

R0

(Z)

Rd

(Z)

Rd

(Z), Z

Z+1

(z)

R1:R0

Rd

P

P

Rr

STACK

Rr

Rd

STACK

(see specific descr. for sleepfunction)

(see specific descr. for WDR/timer)

For on-chip debug only

Flags

H

#Clocks

1

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

None

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

1

2

1

1

3

3

2

2

3

2

2

2

2

2

2

1

1

None

None

None

None

1

1

1

N/A

168 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

25.

Ordering Information

Power Supply Speed (MHz) Ordering Code

ATtiny25/45/85-15ST

ATtiny25/45/85-15ST1 2.7 - 5.5V

8 - 16

(3)

ATtiny25/45/85-15SZ

ATtiny25/45/85-15MT

2.7 - 5.5V

8 - 16

(3)

ATtiny25/45/85-15MT1

ATtiny25/45/85-15MZ

Notes: 1.

Green and ROHS packaging

2.

Tape and Reel with Dry-pack delivery.

3.

For Speed versus V

CC

,see Figure 21-2 on page 139 .

Table 25-1. Package Type

T5

PC

Package

T5

PC

Package Type

T5 - 8-lead, 0.208” body width

Plastic gull wing small outline package

PC - 20-lead, 4.0 x 4.0mm body, 0.50mm pitch

Quad flat no lead package (QFN)

Operation Range

Automotive (–40°C to +85°C)

Automotive (–40°C to +105°C)

Automotive (–40°C to +125°C)

Automotive (–40°C to +85°C)

Automotive (–40°C to +105°C)

Automotive (–40°C to +125°C)

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

169

26.

Packaging Information

26.1

T5

8L SOIC .208

0°~ 8°

E

Pin #1

Identifier

E1

A

L

C e b

D

A1

Base

Plane

Seating

Plane

A

A1 b

C

D

E

E1

L e

Q

Package Drawing Contact:

[email protected]

TITLE

T5, 8-Lead, 0.208” Body Width

Plastic: Quad Wing Small Outline Package (SOIC)

Min

1.70

0.05

0.35

0.15

5.13

7.70

5.18

0.51

MM

Max

2.16

0.25

0.48

0.35

5.35

8.26

5.40

0.85

1.27

Min

.066

.002

.014

.006

.202

.303

.204

.020

INCH

MAx

.085

.010

.015

.014

.211

.325

.212

.033

GPC

07/27/07

DRAWING NO.

REV.

T5

B

170 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

26.2

PC

D

DRAWINGS NOT SCALED ccc

C eee C

A

A1

E

Laser Mark for Pin 1

Identification in this Area

Top View

D2

6 10

5

11

B

E2

1

Pin1 ID

See Option A, B b

20 e

16

Bottom View

L

15

C

Side View

Seating Plane

COMMON DIMENSIONS

(Unit of Measure = mm)

SYMBOL

A

A1

D/E

D2/E2

L b

MIN

0.70

0.00

3.90

2.50

0.35

0.20

NOM

0.75

0.02

4.00

2.60

0.45

0.25

MAX

0.80

0.05

4.10

2.70

0.55

0.30

e 0.50 BSC ccc

Tolerances of Form and Position

0.10

NOTE

eee n

Option A

0.08

20

Option B

Pin 1# Chamfer

(C 0.35 max)

Pin 1# Notch

(0.20 R)

Notes:

1.

2.

This drawing is for general information only. Refer to JEDEC Drawing MO-220, Variation WGGD-5 for proper dimensions, tolerances, datums, etc.

(excepted D2/E2 Min et Nom.)

Dimensions b applies to metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip.

If the terminal has the optical radius on the other end of the terminal, the dimensions should not be measured in that radius area.

GPC

08/01/14

DRAWING NO.

REV.

Package Drawing Contact:

[email protected]

TITLE

PC, 20-Lds - 0.50mm Pitch, 4x4x0.8mm Body size

Very very Thin Quad Flat No Lead Package (WQFN) Sawn

ZVF PC J

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

171

27.

Errata

The revision letter in this section refers to the revision of the Atmel

®

ATtiny25/45/85 device.

27.1

ATtiny25, Revision E

1.

No known errata. Flash security improvements.

27.2

ATtiny45, Revision G

1.

No known errata. Flash security improvements.

27.3

ATtiny85, Revision C

1.

No known errata. Flash security improvements.

28.

Revision History

Please note that the following page numbers referred to in this section refer to the specific revision mentioned, not to this document.

Revision No.

7598J-AVR-12/14

7598I-AVR-10/12

7598H-AVR-07/09

7598G-AVR-03/08

7598F-AVR-11/07

7598E-AVR-03/07

7598D-AVR-02/07

7598C-AVR-09/06

7598B-AVR-08/06

7598A-AVR-04/06

History

Put datasheet in the latest template

Section 27 “Package Information” on page 188 updated

Absolute Maximum Ratings updated

Modified Section 6. “Power Management and Sleep Modes” on page 28

Modified Section 6.1 “MCU Control Register – MCUCR” on page 28

Modified Table 6-2 on page 29 .

Added Section 6.5 “Limitations” on page 29 .

Modified Section 6.6 “Power Reduction Register” on page 30

.

Correction to ICC Active,

Table 21-1 on page 137

.

POR updated, see Section 7.3 “Power-on Reset” on page 34

Clarification of power On reset specifications table.

Errata list updated.

Added QFN packages.

Correction of package codification and drawings.

Clarification of several TBD values

Addition of the power on reset specification

DC characteristics limits completed after corner run characterization

Typical characteristic curves produced

Automotive grade created:

Features:

● Change voltage and temperature range (2.7V – 5.5V), (–40°C, +125°C)

● Adapt Stand-by current to automotive temperature range

Packages:

● PDIP removed

● Ordering info limited to automotive versions (green only, dry pack)

DC and AC parameters

Only PRELIMINARY values are produced

172 ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

29.

Table of Contents

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1

Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2

Automotive Quality Grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.3

Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.

3.

About Code Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

AVR CPU Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.2

Architectural Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.3

ALU – Arithmetic Logic Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.4

Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.5

General Purpose Register File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.6

Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.7

Instruction Execution Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.8

Reset and Interrupt Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.

AVR ATtiny25/45/85 Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.1

In-System Re-programmable Flash Program Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.2

SRAM Data Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.3

EEPROM Data Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.4

I/O Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.

System Clock and Clock Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.1

Clock Systems and their Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.2

Clock Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.3

Default Clock Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.4

Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.5

Low-frequency Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.6

Calibrated Internal RC Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.7

External Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.8

128 kHz Internal Oscillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5.9

Clock Output Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.10

System Clock Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6.

Power Management and Sleep Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6.1

MCU Control Register – MCUCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6.2

Idle Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.3

ADC Noise Reduction Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.4

Power-down Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.5

Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.6

Power Reduction Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6.7

Minimizing Power Consumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7.

System Control and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

7.1

Resetting the AVR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

7.2

Reset Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

7.3

Power-on Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

7.4

External Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

7.5

Brown-out Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

7.6

Watchdog Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

7.7

MCU Status Register – MCUSR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

ATtiny25/45/85 Automotive [DATASHEET]

7598J–AVR–12/14

173

7.8

Internal Voltage Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7.9

Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.10

Timed Sequences for Changing the Configuration of the Watchdog Timer. . . . . . . . . . . . . . 41

8.

Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.1

Interrupt Vectors in ATtiny25/45/85 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

9.

I/O Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

9.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

9.2

Ports as General Digital I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

9.3

Alternate Port Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

9.4

Register Description for I/O-Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

10.

External Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

10.1

MCU Control Register – MCUCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

10.2

General Interrupt Mask Register – GIMSK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

10.3

General Interrupt Flag Register – GIFR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

10.4

Pin Change Mask Register – PCMSK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

11.

8-bit Timer/Counter0 with PWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

11.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

11.2

Timer/Counter Clock Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

11.3

Counter Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

11.4

Output Compare Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

11.5

Compare Match Output Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

11.6

Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

11.7

Timer/Counter Timing Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

11.8

8-bit Timer/Counter Register Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

12.

Timer/Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

12.1

Prescaler Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

12.2

External Clock Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

13.

Counter and Compare Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

13.1

Timer/Counter1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

14.

Dead Time Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

14.1

Timer/Counter1 Dead Time Prescaler register 1 - DTPS1 . . . . . . . . . . . . . . . . . . . . . . . . . . 86

14.2

Timer/Counter1 Dead Time A - DT1A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

14.3

Timer/Counter1 Dead Time B - DT1B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

15.

Universal Serial Interface – USI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

15.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

15.2

Functional Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

15.3

Alternative USI Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

15.4

USI Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

16.

Analog Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

16.1

ADC Control and Status Register B – ADCSRB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

16.2

Analog Comparator Control and Status Register – ACSR. . . . . . . . . . . . . . . . . . . . . . . . . . . 98

16.3

Analog Comparator Multiplexed Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

17.

Analog to Digital Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

17.1

Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

17.2

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

17.3

Starting a Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

17.4

Prescaling and Conversion Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

17.5

Changing Channel or Reference Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

174 ATtiny25/45/85 Automotive [DATASHEET]

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17.6

ADC Noise Canceler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

17.7

ADC Conversion Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

18.

debugWIRE On-chip Debug System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

18.1

Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

18.2

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

18.3

Physical Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

18.4

Software Break Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

18.5

Limitations of debugWIRE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

18.6

debugWIRE Related Register in I/O Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

19.

Self-Programming the Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

19.1

Performing Page Erase by SPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

19.2

Filling the Temporary Buffer (Page Loading) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

19.3

Performing a Page Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

19.4

Addressing the Flash During Self-Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

20.

Memory Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

20.1

Program And Data Memory Lock Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

20.2

Fuse Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

20.3

Signature Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

20.4

Calibration Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

20.5

Page Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

20.6

Serial Downloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

20.7

High-voltage Serial Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

20.8

High-voltage Serial Programming Algorithm Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

20.9

High-voltage Serial Programming Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

21.

Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

21.1

Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

21.2

External Clock Drive Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

21.3

External Clock Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

21.4

ADC Characteristics – Preliminary Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

21.5

Calibrated RC Oscillator Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

22.

Typical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

22.1

Active Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

22.2

Idle Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

22.3

Power-Down Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

22.4

Pin Pull-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

22.5

Pin Driver Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

22.6

Pin Thresholds and Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

22.7

BOD Thresholds and Analog Comparator Offset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

22.8

Internal Oscillator Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

22.9

Current Consumption of Peripheral Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

22.10 Current Consumption in Reset and Reset Pulse width . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

22.11 Analog to Digital Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

23.

Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

24.

Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

25.

Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

26.

Packaging Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

26.1

T5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

26.2

PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

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175

27.

Errata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

27.1

ATtiny25, Revision E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

27.2

ATtiny45, Revision G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

27.3

ATtiny85, Revision C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

28.

Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

29.

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

176 ATtiny25/45/85 Automotive [DATASHEET]

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X

X X X X X

Atmel Corporation

1600 Technology Drive, San Jose, CA 95110 USA T: (+1)(408) 441.0311

F: (+1)(408) 436.4200

| www.atmel.com

© 2014 Atmel Corporation. / Rev.: 7598J–AVR–12/14

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, Atmel logo and combinations thereof, Enabling Unlimited Possibilities

®

, AVR

®

, AVR Studio

®

, and others are registered trademarks or trademarks of Atmel

Corporation in U.S. and other countries. Other terms and product names may be trademarks of others.

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SAFETY-CRITICAL, MILITARY, AND AUTOMOTIVE APPLICATIONS DISCLAIMER: Atmel products are not designed for and will not be used in connection with any applications where the failure of such products would reasonably be expected to result in significant personal injury or death (“Safety-Critical Applications”) without an Atmel officer's specific written consent. Safety-Critical Applications include, without limitation, life support devices and systems, equipment or systems for the operation of nuclear facilities and weapons systems.

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