Datasheet
Table Of Contents
- Features
- Pin Configurations
- Overview
- Resources
- Data Retention
- About Code Examples
- Atmel AVR CPU Core
- AVR ATmega8 Memories
- System Clock and Clock Options
- Power Management and Sleep Modes
- System Control and Reset
- Interrupts
- I/O Ports
- Introduction
- Ports as General Digital I/O
- Alternate Port Functions
- Register Description for I/O Ports
- The Port B Data Register – PORTB
- The Port B Data Direction Register – DDRB
- The Port B Input Pins Address – PINB
- The Port C Data Register – PORTC
- The Port C Data Direction Register – DDRC
- The Port C Input Pins Address – PINC
- The Port D Data Register – PORTD
- The Port D Data Direction Register – DDRD
- The Port D Input Pins Address – PIND
- External Interrupts
- 8-bit Timer/Counter0
- Timer/Counter0 and Timer/Counter1 Prescalers
- 16-bit Timer/Counter1
- Overview
- Accessing 16-bit Registers
- Timer/Counter Clock Sources
- Counter Unit
- Input Capture Unit
- Output Compare Units
- Compare Match Output Unit
- Modes of Operation
- Timer/Counter Timing Diagrams
- 16-bit Timer/Counter Register Description
- Timer/Counter 1 Control Register A – TCCR1A
- Timer/Counter 1 Control Register B – TCCR1B
- Timer/Counter 1 – TCNT1H and TCNT1L
- Output Compare Register 1 A – OCR1AH and OCR1AL
- Output Compare Register 1 B – OCR1BH and OCR1BL
- Input Capture Register 1 – ICR1H and ICR1L
- Timer/Counter Interrupt Mask Register – TIMSK(1)
- Timer/Counter Interrupt Flag Register – TIFR(1)
- 8-bit Timer/Counter2 with PWM and Asynchronous Operation
- Serial Peripheral Interface – SPI
- USART
- Two-wire Serial Interface
- Analog Comparator
- Analog-to- Digital Converter
- Boot Loader Support – Read- While-Write Self- Programming
- Boot Loader Features
- Application and Boot Loader Flash Sections
- Read-While-Write and No Read- While-Write Flash Sections
- Boot Loader Lock Bits
- Entering the Boot Loader Program
- Addressing the Flash During Self- Programming
- Self-Programming the Flash
- Performing Page Erase by SPM
- Filling the Temporary Buffer (Page Loading)
- Performing a Page Write
- Using the SPM Interrupt
- Consideration While Updating BLS
- Prevent Reading the RWW Section During Self-Programming
- Setting the Boot Loader Lock Bits by SPM
- EEPROM Write Prevents Writing to SPMCR
- Reading the Fuse and Lock Bits from Software
- Preventing Flash Corruption
- Programming Time for Flash when using SPM
- Simple Assembly Code Example for a Boot Loader
- ATmega8 Boot Loader Parameters
- Memory Programming
- Program And Data Memory Lock Bits
- Fuse Bits
- Signature Bytes
- Calibration Byte
- Page Size
- Parallel Programming Parameters, Pin Mapping, and Commands
- Parallel Programming
- Enter Programming Mode
- Considerations for Efficient Programming
- Chip Erase
- Programming the Flash
- Programming the EEPROM
- Reading the Flash
- Reading the EEPROM
- Programming the Fuse Low Bits
- Programming the Fuse High Bits
- Programming the Lock Bits
- Reading the Fuse and Lock Bits
- Reading the Signature Bytes
- Reading the Calibration Byte
- Parallel Programming Characteristics
- Serial Downloading
- Serial Programming Pin Mapping
- Electrical Characteristics – TA = -40°C to 85°C
- Electrical Characteristics – TA = -40°C to 105°C
- ATmega8 Typical Characteristics – TA = -40°C to 85°C
- Active Supply Current
- Idle Supply Current
- Power-down Supply Current
- Power-save Supply Current
- Standby Supply Current
- Pin Pull-up
- Pin Driver Strength
- Pin Thresholds and Hysteresis
- Bod Thresholds and Analog Comparator Offset
- Internal Oscillator Speed
- Current Consumption of Peripheral Units
- Current Consumption in Reset and Reset Pulsewidth
- ATmega8 Typical Characteristics – TA = -40°C to 105°C
- Register Summary
- Instruction Set Summary
- Ordering Information
- Packaging Information
- Errata
- Datasheet Revision History
- Changes from Rev. 2486Z- 02/11 to Rev. 2486AA- 02/2013
- Changes from Rev. 2486Y- 10/10 to Rev. 2486Z- 02/11
- Changes from Rev. 2486X- 06/10 to Rev. 2486Y- 10/10
- Changes from Rev. 2486W- 02/10 to Rev. 2486X- 06/10
- Changes from Rev. 2486V- 05/09 to Rev. 2486W- 02/10
- Changes from Rev. 2486U- 08/08 to Rev. 2486V- 05/09
- Changes from Rev. 2486T- 05/08 to Rev. 2486U- 08/08
- Changes from Rev. 2486S- 08/07 to Rev. 2486T- 05/08
- Changes from Rev. 2486R- 07/07 to Rev. 2486S- 08/07
- Changes from Rev. 2486Q- 10/06 to Rev. 2486R- 07/07
- Changes from Rev. 2486P- 02/06 to Rev. 2486Q- 10/06
- Changes from Rev. 2486O-10/04 to Rev. 2486P- 02/06
- Changes from Rev. 2486N-09/04 to Rev. 2486O-10/04
- Changes from Rev. 2486M-12/03 to Rev. 2486N-09/04
- Changes from Rev. 2486L-10/03 to Rev. 2486M-12/03
- Changes from Rev. 2486K-08/03 to Rev. 2486L-10/03
- Changes from Rev. 2486J-02/03 to Rev. 2486K-08/03
- Changes from Rev. 2486I-12/02 to Rev. 2486J-02/03
- Changes from Rev. 2486H-09/02 to Rev. 2486I-12/02
- Changes from Rev. 2486G-09/02 to Rev. 2486H-09/02
- Changes from Rev. 2486F-07/02 to Rev. 2486G-09/02
- Changes from Rev. 2486E-06/02 to Rev. 2486F-07/02
- Changes from Rev. 2486D-03/02 to Rev. 2486E-06/02
- Changes from Rev. 2486C-03/02 to Rev. 2486D-03/02
- Changes from Rev. 2486B-12/01 to Rev. 2486C-03/02
- Table of Contents
46
2486AA–AVR–02/2013
ATmega8(L)
Interrupts This section describes the specifics of the interrupt handling performed by the ATmega8. For a
general explanation of the AVR interrupt handling, refer to “Reset and Interrupt Handling” on
page 14.
Interrupt Vectors
in ATmega8
Notes: 1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader address at
reset, see “Boot Loader Support – Read-While-Write Self-Programming” on page 202
2. When the IVSEL bit in GICR is set, Interrupt Vectors will be moved to the start of the boot
Flash section. The address of each Interrupt Vector will then be the address in this table added
to the start address of the boot Flash section
Table 19 on page 47 shows reset and Interrupt Vectors placement for the various combinations
of BOOTRST and IVSEL settings. If the program never enables an interrupt source, the Interrupt
Vectors are not used, and regular program code can be placed at these locations. This is also
the case if the Reset Vector is in the Application section while the Interrupt Vectors are in the
boot section or vice versa.
Table 18. Reset and Interrupt Vectors
Vector No.
Program
Address
(2)
Source Interrupt Definition
1 0x000
(1)
RESET External Pin, Power-on Reset, Brown-out
Reset, and Watchdog Reset
2 0x001 INT0 External Interrupt Request 0
3 0x002 INT1 External Interrupt Request 1
4 0x003 TIMER2 COMP Timer/Counter2 Compare Match
5 0x004 TIMER2 OVF Timer/Counter2 Overflow
6 0x005 TIMER1 CAPT Timer/Counter1 Capture Event
7 0x006 TIMER1 COMPA Timer/Counter1 Compare Match A
8 0x007 TIMER1 COMPB Timer/Counter1 Compare Match B
9 0x008 TIMER1 OVF Timer/Counter1 Overflow
10 0x009 TIMER0 OVF Timer/Counter0 Overflow
11 0x00A SPI, STC Serial Transfer Complete
12 0x00B USART, RXC USART, Rx Complete
13 0x00C USART, UDRE USART Data Register Empty
14 0x00D USART, TXC USART, Tx Complete
15 0x00E ADC ADC Conversion Complete
16 0x00F EE_RDY EEPROM Ready
17 0x010 ANA_COMP Analog Comparator
18 0x011 TWI Two-wire Serial Interface
19 0x012 SPM_RDY Store Program Memory Ready