The ATmega8 is old - it was the original MCU in the Arduino - but it is still one of the most popular AVRs. They have been obsoleted technically by the bigger, faster, cheaper, and lower power ATmega168 and ATmega328 devices.
The ATmega8 has a different clock than many other AVR's, featuring an internal clock that runs at 1MHz, 2MHz, 4MHz, and 8MHz, rather than having a divide by 8 fuse. The maximum frequency is 16MHz with an external crystal.
The calculator below provides a way to find the maximum operating frequency for any valid power supply voltage (2.7 to 5.5). Enter the power supply voltage and click "Calculate Max Frequency" to find the ATmega8's specified maximum frequency at your Vcc.
|Power Consumption (approximate)||0.6mA/MHz|
|Maximum I/O Current (per pin)||40mA|
|Maximum I/O Current (all ports)||100mA(low)/150mA(high)|
|Maximum I/O Current (total)||200mA (PDIP)|
|Maximum I/O Current (total)||400mA (PDIP/QFP/MLF)|
A minimal ATmega8 circuit consists of an ATmega8. Everything else is optional. The circuit below shows a programming port, reset circuit, and a crystal oscillator. Any or all of these could be left off and the device would function perfectly well. By default the unit runs from the 1MHz internal RC oscillator.