Jump to main content
ATmega8A Data Sheet
Introduction
Features
1 Description
2 Configuration Summary
3 Ordering Information
4 Block Diagram
5 Pin Configurations
5.1 Pin Descriptions
5.2 Accessing 16-bit Registers
6 I/O Multiplexing
7 Resources
8 Data Retention
9 About Code Examples
10 Capacitive Touch Sensing
10.1 QTouch Library
11 AVR CPU Core
11.1 Overview
11.2 ALU – Arithmetic Logic Unit
11.3 Status Register
11.4 General Purpose Register File
11.5 Stack Pointer
11.6 Instruction Execution Timing
11.7 Reset and Interrupt Handling
12 AVR Memories
12.1 Overview
12.2 In-System Reprogrammable Flash Program Memory
12.3 SRAM Data Memory
12.4 EEPROM Data Memory
12.5 I/O Memory
12.6 Register Description
13 System Clock and Clock Options
13.1 Clock Systems and their Distribution
13.2 Clock Sources
13.3 Crystal Oscillator
13.4 Low-frequency Crystal Oscillator
13.5 External RC Oscillator
13.6 Calibrated Internal RC Oscillator
13.7 External Clock
13.8 Timer/Counter Oscillator
13.9 Register Description
14 Power Management and Sleep Modes
14.1 Sleep Modes
14.2 Idle Mode
14.3 ADC Noise Reduction Mode
14.4 Power-down Mode
14.5 Power-save Mode
14.6 Standby Mode
14.7 Minimizing Power Consumption
14.8 Register Description
15 System Control and Reset
15.1 Resetting the AVR
15.2 Reset Sources
15.3 Internal Voltage Reference
15.4 Watchdog Timer
15.5 Timed Sequences for Changing the Configuration of the Watchdog Timer
15.6 Register Description
16 Interrupts
16.1 Interrupt Vectors in ATmega8A
16.2 Register Description
17 External Interrupts
17.1 Register Description
18 I/O Ports
18.1 Overview
18.2 Ports as General Digital I/O
18.3 Alternate Port Functions
18.4 Register Description
19 8-bit Timer/Counter0
19.1 Features
19.2 Overview
19.3 Timer/Counter Clock Sources
19.4 Counter Unit
19.5 Operation
19.6 Timer/Counter Timing Diagrams
19.7 Register Description
20 Timer/Counter0 and Timer/Counter1 Prescalers
20.1 Overview
20.2 Internal Clock Source
20.3 Prescaler Reset
20.4 External Clock Source
20.5 Register Description
21 16-bit Timer/Counter1
21.1 Features
21.2 Overview
21.3 Accessing 16-bit Registers
21.4 Timer/Counter Clock Sources
21.5 Counter Unit
21.6 Input Capture Unit
21.7 Output Compare Units
21.8 Compare Match Output Unit
21.9 Modes of Operation
21.10 Timer/Counter Timing Diagrams
21.11 Register Description
22 8-bit Timer/Counter2 with PWM and Asynchronous Operation
22.1 Features
22.2 Overview
22.3 Timer/Counter Clock Sources
22.4 Counter Unit
22.5 Output Compare Unit
22.6 Compare Match Output Unit
22.7 Modes of Operation
22.8 Timer/Counter Timing Diagrams
22.9 Asynchronous Operation of the Timer/Counter
22.10 Timer/Counter Prescaler
22.11 Register Description
23 SPI – Serial Peripheral Interface
23.1 Features
23.2 Overview
23.3 SS Pin Functionality
23.4 Data Modes
23.5 Register Description
24 USART - Universal Synchronous and Asynchronous serial Receiver and Transmitter
24.1 Features
24.2 Overview
24.3 Clock Generation
24.4 Frame Formats
24.5 USART Initialization
24.6 Data Transmission – The USART Transmitter
24.7 Data Reception – The USART Receiver
24.8 Asynchronous Data Reception
24.9 Multi-Processor Communication Mode
24.10 Accessing UBRRH/UCSRC Registers
24.11 Register Description
24.12 Examples of Baud Rate Setting
25 TWI - Two-wire Serial Interface
25.1 Features
25.2 Overview
25.3 Two-Wire Serial Interface Bus Definition
25.4 Data Transfer and Frame Format
25.5 Multi-master Bus Systems, Arbitration and Synchronization
25.6 Using the TWI
25.7 Multi-master Systems and Arbitration
25.8 Register Description
26 AC - Analog Comparator
26.1 Overview
26.2 Analog Comparator Multiplexed Input
26.3 Register Description
27 ADC - Analog to Digital Converter
27.1 Features
27.2 Overview
27.3 Starting a Conversion
27.4 Prescaling and Conversion Timing
27.5 Changing Channel or Reference Selection
27.6 ADC Noise Canceler
27.7 ADC Conversion Result
27.8 Register Description
28 BTLDR - Boot Loader Support – Read-While-Write Self-Programming
28.1 Features
28.2 Overview
28.3 Application and Boot Loader Flash Sections
28.4 Read-While-Write and No Read-While-Write Flash Sections
28.5 Boot Loader Lock Bits
28.6 Entering the Boot Loader Program
28.7 Addressing the Flash During Self-Programming
28.8 Self-Programming the Flash
28.9 Register Description
29 MEMPROG- Memory Programming
29.1 Program and Data Memory Lock Bits
29.2 Fuse Bits
29.3 Signature Bytes
29.4 Calibration Byte
29.5 Page Size
29.6 Parallel Programming Parameters, Pin Mapping, and Commands
29.7 Parallel Programming
29.8 Serial Downloading
29.9 Serial Programming Pin Mapping
30 Electrical Characteristics – TA = -40°C to 85°C
30.1 DC Characteristics
30.2 Speed Grades
30.3 Clock Characteristics
30.4 System and Reset Characteristics
30.5 Two-wire Serial Interface Characteristics
30.6 SPI Timing Characteristics
30.7 ADC Characteristics
31 Electrical Characteristics – TA = -40°C to 105°C
31.1 DC Characteristics
32 Typical Characteristics – TA = -40°C to 85°C
32.1 Active Supply Current
32.2 Idle Supply Current
32.3 Power-down Supply Current
32.4 Power-save Supply Current
32.5 Standby Supply Current
32.6 Pin Pull-up
32.7 Pin Driver Strength
32.8 Pin Thresholds and Hysteresis
32.9 Bod Thresholds and Analog Comparator Offset
32.10 Internal Oscillator Speed
32.11 Current Consumption of Peripheral Units
32.12 Current Consumption in Reset and Reset Pulsewidth
33 Typical Characteristics – TA = -40°C to 105°C
33.1 ATmega8A Typical Characteristics
34 Register Summary
35 Instruction Set Summary
36 Packaging Information
36.1 32-pin 32A
36.2 28-pin 28P3
36.3 32-pin 32M1-A
37 Errata
37.1 ATmega8A, rev. L
38 Appendix A: Revision History
The Microchip Web Site
Customer Change Notification Service
Customer Support
Microchip Devices Code Protection Feature
Legal Notice
Trademarks
Quality Management System Certified by DNV
Worldwide Sales and Service

The online versions of the documents are provided as a courtesy. Verify all content and data in the device’s PDF documentation found on the device product page.