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Atmega8 Datasheet and the Explanation of The Input Output Pin Features

atmega8 microcontroller pin features

atmega8 microcontroller pin features

In this article described the hardware features of the AVR ATMega atmega 8 that is devoted to the type of PDIP, so for other types (QFN / MLF, TQPF) please refer to the specific datasheet only.

In addition to functioning as an input/output pins, a pin on AVR microcontroller can concurrently as other functions. For example at the AVR ATMega 8 microcontroller, PORTD.2 is an input / output pins, but this pin can also function as a trigger channel “external interrupt 0”. For more details, please follow the following explanation:

Description pin features on ATMega 8:

-VCC: supply voltage Microcontroller
-Ground: Ground

– Port B is a port i / o 8bit with internal pull-up resistors on each pin.
– Buffer on port B AVR ATMega8 have the capacity to absorb (sink) and distribute (sorce)
– Lodging in PB.6 can be used as a crystal input (inverting oscillator amplifier) and input to the internal clock circuit depends on the setting of fuse bits (currently set software downloader / programmer) is used as a clock source.
– Especially for PB.7 port can be used as a crystal output (inverting oscillator amplifier output) depends upon the setting of fuse bits are used to select the clock source.

– If the clock source is the internal oscillator (internal clock, then PB6 and PB7 pin can be used as input / output (I / O pin) or if using Asyncronousu Timer / Counter2 then PB6 and PB7 (TOSC2 and TOSC1) used for counter input channels.

– PORTC.0 – PORTC.5 are input / output ports with internal pull-up resistor for each pin. Buffer in this PORT has the capacity to absorb (sink) and distribute (sorce). In addition, the PORTC in atmega8 microcontroller can function as port ADC (analog to digital converter).

– Reset / PORTC.6, is a pin that can function as a reset pin on the microcontroller program cycle. By way RSTDISBL fuse bit set as “unprogramed” and will be active when it gets a signal “low”. But if RSTDISBL set as “programed” then portC.6 will be used as input / usual output pins.

-PORTD.0 – PORTD.7 are input / output ports with internal pull-up resistor for each pin. Buffer Portc have the capacity to absorb (sink) and distribute (sorce).
– AVCC is the supply voltage pin for the analog to digital converter (ADC). Note: PORTC.5 and PORTC.6 using digital VCC supply voltage.
– Aref is an analog reference voltage pin for ADC

AVR Microcontroller Architecture

avr architecture

avr architecture

AVR microcontroller has some parts that are divided into:

  • ALU (Arithmetic Logic Unit) is a processor for executing the program code that is appointed by the counter program.

  • Program memory is a flash memory to store programs in the form of a memory address and program code in the memory address.
  • Program Counter (PC) is a component to show the address of the program memory. So that ALU can make the execution of programs that exist in the address.

  • General Purpose Working Registers (GPR) is a register that has 8-bit space. GPR will execute program code each instruction in the ALU involving GPR.
  • Static Random Access Memory (SRAM) is RAM that hold the temporarily data. SRAM also has a memory address of the usual RAM. Last address of an SRAM depends on the capacity of SRAM and is already defined in the header file with the name RAMEND. So, to make the stack (the last address of SRAM) we can use RAMEND.

  • Internal pheripheral is an internal module in a microcontroller such as channel input / output, external interrupts, timers / counters, USART, EEPROM, and others. Each of these modules have internal port registers which control the internal module.

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