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
97
2486AA–AVR–02/2013
ATmega8(L)
Table 38 shows the COM1x1:0 bit functionality when the WGM13:0 bits are set to the phase cor-
rect or the phase and frequency correct, PWM mode.
Note: 1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set. See
“Phase Correct PWM Mode” on page 90 for more details
• Bit 3 – FOC1A: Force Output Compare for channel A
• Bit 2 – FOC1B: Force Output Compare for channel B
The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM mode.
However, for ensuring compatibility with future devices, these bits must be set to zero when
TCCR1A is written when operating in a PWM mode. When writing a logical one to the
FOC1A/FOC1B bit, an immediate Compare Match is forced on the waveform generation unit.
The OC1A/OC1B output is changed according to its COM1x1:0 bits setting. Note that the
FOC1A/FOC1B bits are implemented as strobes. Therefore it is the value present in the
COM1x1:0 bits that determine the effect of the forced compare.
A FOC1A/FOC1B strobe will not generate any interrupt nor will it clear the timer in Clear Timer
on Compare Match (CTC) mode using OCR1A as TOP.
The FOC1A/FOC1B bits are always read as zero.
• Bit 1:0 – WGM11:0: Waveform Generation Mode
Combined with the WGM13:2 bits found in the TCCR1B Register, these bits control the counting
sequence of the counter, the source for maximum (TOP) counter value, and what type of wave-
form generation to be used, see Table 39. Modes of operation supported by the Timer/Counter
unit are: Normal mode (counter), Clear Timer on Compare Match (CTC) mode, and three types
of Pulse Width Modulation (PWM) modes (see “Modes of Operation” on page 87).
Table 38. Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
(1)
COM1A1/
COM1B1
COM1A0/
COM1B0 Description
0 0 Normal port operation, OC1A/OC1B disconnected.
0 1 WGM13:0 = 9 or 14: Toggle OC1A on Compare Match, OC1B
disconnected (normal port operation). For all other WGM1
settings, normal port operation, OC1A/OC1B disconnected.
1 0 Clear OC1A/OC1B on Compare Match when up-counting. Set
OC1A/OC1B on Compare Match when downcounting.
1 1 Set OC1A/OC1B on Compare Match when up-counting. Clear
OC1A/OC1B on Compare Match when downcounting.
Table 39. Waveform Generation Mode Bit Description
Mode WGM13
WGM12
(CTC1)
WGM11
(PWM11)
WGM10
(PWM10)
Timer/Counter Mode of
Operation
(1)
TOP
Update of
OCR1x
TOV1 Flag
Set on
0 0 0 0 0 Normal 0xFFFF Immediate MAX
1 0 0 0 1 PWM, Phase Correct, 8-bit 0x00FF TOP BOTTOM
2 0 0 1 0 PWM, Phase Correct, 9-bit 0x01FF TOP BOTTOM
3 0 0 1 1 PWM, Phase Correct, 10-bit 0x03FF TOP BOTTOM
4 0 1 0 0 CTC OCR1A Immediate MAX
5 0 1 0 1 Fast PWM, 8-bit 0x00FF BOTTOM TOP
6 0 1 1 0 Fast PWM, 9-bit 0x01FF BOTTOM TOP