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
318
2486AA–AVR–02/2013
ATmega8(L)
Errata The revision letter in this section refers to the revision of the ATmega8 device.
ATmega8
Rev. D to I, M
• First Analog Comparator conversion may be delayed
• Interrupts may be lost when writing the timer registers in the asynchronous timer
• Signature may be Erased in Serial Programming Mode
• CKOPT Does not Enable Internal Capacitors on XTALn/TOSCn Pins when 32KHz Oscillator is
Used to Clock the Asynchronous Timer/Counter2
• Reading EEPROM by using ST or STS to set EERE bit triggers unexpected interrupt request
1. First Analog Comparator conversion may be delayed
If the device is powered by a slow rising V
CC
, the first Analog Comparator conversion will
take longer than expected on some devices.
Problem Fix / Workaround
When the device has been powered or reset, disable then enable theAnalog Comparator
before the first conversion.
2. Interrupts may be lost when writing the timer registers in the asynchronous timer
The interrupt will be lost if a timer register that is synchronized to the asynchronous timer
clock is written when the asynchronous Timer/Counter register(TCNTx) is 0x00.
Problem Fix / Workaround
Always check that the asynchronous Timer/Counter register neither have the value 0xFF nor
0x00 before writing to the asynchronous Timer Control Register(TCCRx), asynchronous
Timer Counter Register(TCNTx), or asynchronous Output Compare Register(OCRx).
3. Signature may be Erased in Serial Programming Mode
If the signature bytes are read before a chiperase command is completed, the signature may
be erased causing the device ID and calibration bytes to disappear. This is critical, espe-
cially, if the part is running on internal RC oscillator.
Problem Fix / Workaround:
Ensure that the chiperase command has exceeded before applying the next command.
4. CKOPT Does not Enable Internal Capacitors on XTALn/TOSCn Pins when 32KHz
Oscillator is Used to Clock the Asynchronous Timer/Counter2
When the internal RC Oscillator is used as the main clock source, it is possible to run the
Timer/Counter2 asynchronously by connecting a 32KHz Oscillator between XTAL1/TOSC1
and XTAL2/TOSC2. But when the internal RC Oscillator is selected as the main clock
source, the CKOPT Fuse does not control the internal capacitors on XTAL1/TOSC1 and
XTAL2/TOSC2. As long as there are no capacitors connected to XTAL1/TOSC1 and
XTAL2/TOSC2, safe operation of the Oscillator is not guaranteed.
Problem Fix / Workaround
Use external capacitors in the range of 20pF - 36pF on XTAL1/TOSC1 and XTAL2/TOSC2.
This will be fixed in ATmega8 Rev. G where the CKOPT Fuse will control internal capacitors
also when internal RC Oscillator is selected as main clock source. For ATmega8 Rev. G,
CKOPT = 0 (programmed) will enable the internal capacitors on XTAL1 and XTAL2. Cus-
tomers who want compatibility between Rev. G and older revisions, must ensure that
CKOPT is unprogrammed (CKOPT = 1).