AVR ATMEGA 8

MICRO-CONTROLLER

INTRODUCTION• ATmega8 is a 8-bit microcontroller based on

the AVR RISC architecture• By executing powerful instructions in a single

clock cycle, the ATmega8 achieves throughput approaching 1 MIPS per MHz

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• In order to maximize performance and parallelism, the AVR uses a Harvard architecture- which separates memories and buses for program and data

• Instruction in program memory are executed with single level pipelining

• This concept enables instructions to be executed in every clock cycle

FEATURES• High-performance 8 bit Microcontroller• Up to 16 MIPS Throughput at 16 MHz• 32 x 8 General Purpose Working Registers• Six ADC channels in PDIP package• Internal Calibrated Oscillator

TYPES OF PACKAGES

• 28-pin PDIP (Plastic Dual In-line Package)• 32-pin TQFP (Thin Quad film Package)

MEMORY SEGMENTS• 8K Bytes of Flash program memory• 512 Bytes EEPROM (Electrically Erasable

Programmable Read Only Memory)• 1K Byte Internal RAM (Random Access

Memory)

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• Write/Erase Cycles: 10,000 Flash/100,000 EEPROM

• Data retention: 20 years at 85°C/100 years at 25°C

PIN OUT

PIN DESCRIPTION• VCC Digital supply voltage• GND Ground• RESET A low level on this pin for longer than

the minimum pulse length will generate a reset, even if the clock is not running

• AREF The analog reference pin for the A/D Converter

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• AVCC The supply voltage pin for the A/D Converter

PORTS• Three ports i.e PortB, PortC, PortD• Three registers associated with every port DDRx – Data Direction Register PINx – Port input PORTx- Port output

*Note – ‘x’ is subscript and could be either of B, C, D

Port B (PB7..PB0)

• Port B is an 8-bit bi-directional I/O port

• Can be used either as a input port or as output port ( direction must be specified in programming)

REGISTER DESCRIPTION OF I/O PORTS

Port C (PC5..PC0)

• Port C is an 7-bit bi-directional I/O port

• Can be used either as a input port or as output port ( direction must be specified in programming)

Port D (PD7..PD0)

• Port D is an 8-bit bi-directional I/O port

• Can be used either as a input port or as output port ( direction must be specified in coding)

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Thank you…