Atmel ATtiny85 User Manual

124
7598H–AVR–07/09
ATtiny25/45/85
• 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 mea-
surements. Selecting the single-ended channel ADC4 enables the temperature sensor. Refer to
Table 18-4 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).
18.7.6 ADC Control and Status Register A – ADCSRA
• 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.
Table 18-4. Input Channel Selections
MUX3..0
Single Ended
Input
Positive
Differential Input
Negative
Differential Input Gain
0000 ADC0 (PB5)
N/A
0001 ADC1 (PB2)
0010 ADC2 (PB4)
0011 ADC3 (PB3)
0100
N/A
ADC2 (PB3) ADC2 (PB3) 1x
0101
(1)
1. For offset calibration only . See “Operation” on page 112.
ADC2 (PB3) ADC2 (PB3) 20x
0110 ADC2 (PB3) ADC3 (PB4) 1x
0111 ADC2 (PB3) ADC3 (PB4) 20x
1000 ADC0 (PB5) ADC0 (PB5) 1x
1001 ADC0 (PB5) ADC0 (PB5) 20x
1010 ADC0 (PB5) ADC1 (PB2) 1x
1011 ADC0 (PB5) ADC1 (PB2) 20x
1100 1.1V/2.56V
N/A
1101 0V
1110 N/A
1111 ADC4
(2)
2. For Temperature Sensor
Bit 76543210
ADEN ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0 ADCSRA
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0

Atmel ATtiny85 Specifications

General

Architecture	8-bit AVR
Flash Memory	8 KB
SRAM	512 B
EEPROM	512 B
Clock Speed	20 MHz
GPIO Pins	6
ADC Channels	4
ADC Resolution	10-bit
Timers	2 (8-bit)
PWM Channels	2
Operating Voltage	2.7V - 5.5V
Communication Interfaces	SPI, I2C
Package	DIP-8, SOIC-8
Operating Temperature	-40°C to 85°C

Summary

ATtiny25/45/85 Features Overview

High-Performance AVR Microcontroller

Details on the advanced RISC architecture and its benefits for performance.

Non-volatile Program and Data Memories

Information on Flash, EEPROM, and SRAM capacities and endurance.

Peripheral Features

Overview of integrated peripherals like Timers, ADC, and USI.

Low Power Consumption

ATtiny25/45/85 Pin Configuration

ATtiny25/45/85 Block Diagram

ATtiny25/45/85 Pin Descriptions

AVR CPU Core

Architectural Overview

Explanation of the Harvard architecture and pipelining.

General Purpose Register File

Reset and Interrupt Handling

Explanation of reset sources and interrupt vector handling.

AVR ATtiny25/45/85 Memories

In-System Re-programmable Flash Program Memory

Details on Flash memory size, endurance, and programming.

SRAM Data Memory Organization

Description of SRAM organization and addressing modes.

EEPROM Data Memory

Information on EEPROM capacity, endurance, and access.

System Clock and Clock Options

Clock Sources

System Clock Prescaler

Explanation of the Clock Prescale Register (CLKPR) for clock frequency control.

Power Management and Sleep Modes

MCU Control Register (MCUCR)

Power-down Mode Operation

Minimizing Power Consumption

Strategies for reducing power consumption in the device.

System Control and Reset

Reset Sources

Overview of the four reset sources: Power-on, External, Watchdog, Brown-out.

Power-on Reset (POR)

Details on the POR circuit, detection level, and start-up timing.

External Reset

Brown-out Detection (BOD)

Information on the on-chip BOD circuit and selectable trigger levels.

Watchdog Timer

Details on the Watchdog Timer operation, configuration, and reset.

Interrupts

Interrupt Vectors in ATtiny25/45/85

I/O Ports

Ports as General Digital I/O

External Interrupts

8-bit Timer/Counter0 with PWM

Overview of Timer/Counter0

Modes of Operation

Explanation of Normal, CTC, Fast PWM, and Phase Correct PWM modes.

8-bit Timer/Counter Register Description

Counter and Compare Units

Timer/Counter1 Overview

Timer/Counter1 in PWM Mode

Details on generating PWM waveforms with Timer/Counter1.

Universal Serial Interface (USI)

Overview of USI

Two-wire Mode Operation

Analog Comparator

Analog Comparator Control and Status Register (ACSR)

Analog to Digital Converter (ADC)

ADC Features

Overview of ADC resolution, conversion time, and input channels.

ADC Operation

Explanation of the ADC conversion process and voltage references.

Starting a Conversion

Methods for initiating ADC conversions, including auto-triggering.

ADC Conversion Result

Details on how the conversion result is presented and interpreted.

ADC Multiplexer Selection Register (ADMUX)

ADC Control and Status Register A (ADCSRA)

debugWIRE On-chip Debug System

debugWIRE Features

Self-Programming the Flash

Performing Page Erase by SPM

Filling the Temporary Buffer (Page Loading)

Memory Programming

Fuse Bytes Overview

Serial Downloading

High-voltage Serial Programming

Procedures for programming Flash, EEPROM, Lock bits, and Fuses.

Electrical Characteristics

Absolute Maximum Ratings

DC Characteristics

Typical Characteristics