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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 ATMega8 Schematic Circuit with Eagle Software



ATMega8 Schematic Circuit (Minimum system) is a support circuit for the microcontroller.

Without this support circuit, the microcontroller will not be able to work.

Minimum system for microcontrollers consist of several components. The components are : crystal, capacitors, and the reset circuit (consisting of resistors and capacitors).

And the crystal must be combined by two capacitors. The capacity of this capacitor should be in accordance with the AVR ATMega8 datasheet.

RESET pin on AVR ATMega8 must be pull up with a 4K7 ohm resistor and stabilized with ‘100nF capacitors’.

You have to make the pin as a downloader port. pin of the downloader port must meet a standard sequence. The pin sequence is: MOSI, MISO, SCK, RESET, GROUND.

This AVR ATMega8 schematic is made with the EAGLE software.