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
59
2486AA–AVR–02/2013
ATmega8(L)
• SCK – Port B, Bit 5
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 DDB5. When the SPI is
enabled as a Master, the data direction of this pin is controlled by DDB5. When the pin is forced
by the SPI to be an input, the pull-up can still be controlled by the PORTB5 bit.
• MISO – Port B, Bit 4
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 DDB4. When the SPI is
enabled as a Slave, the data direction of this pin is controlled by DDB4. When the pin is forced
by the SPI to be an input, the pull-up can still be controlled by the PORTB4 bit.
• MOSI/OC2 – Port B, Bit 3
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 DDB3. When the SPI is
enabled as a Master, the data direction of this pin is controlled by DDB3. When the pin is forced
by the SPI to be an input, the pull-up can still be controlled by the PORTB3 bit.
OC2, Output Compare Match Output: The PB3 pin can serve as an external output for the
Timer/Counter2 Compare Match. The PB3 pin has to be configured as an output (DDB3 set
(one)) to serve this function. The OC2 pin is also the output pin for the PWM mode timer
function.
•SS
/OC1B – Port B, Bit 2
SS
: Slave Select input. When the SPI is enabled as a Slave, this pin is configured as an input
regardless of the setting of DDB2. As a Slave, the SPI is activated when this pin is driven low.
When the SPI is enabled as a Master, the data direction of this pin is controlled by DDB2. When
the pin is forced by the SPI to be an input, the pull-up can still be controlled by the PORTB2 bit.
OC1B, Output Compare Match output: The PB2 pin can serve as an external output for the
Timer/Counter1 Compare Match B. The PB2 pin has to be configured as an output (DDB2 set
(one)) to serve this function. The OC1B pin is also the output pin for the PWM mode timer
function.
• OC1A – Port B, Bit 1
OC1A, Output Compare Match output: The PB1 pin can serve as an external output for the
Timer/Counter1 Compare Match A. The PB1 pin has to be configured as an output (DDB1 set
(one)) to serve this function. The OC1A pin is also the output pin for the PWM mode timer
function.
• ICP1 – Port B, Bit 0
ICP1 – Input Capture Pin: The PB0 pin can act as an Input Capture Pin for Timer/Counter1.
Table 23 on page 60 and Table 24 on page 60 relate the alternate functions of Port B to the
overriding signals shown in Figure 25 on page 56. SPI MSTR INPUT and SPI SLAVE OUTPUT
constitute the MISO signal, while MOSI is divided into SPI MSTR OUTPUT and SPI SLAVE
INPUT.