Electronic – default Clock Frequency for Atmega8

atmegaavrclock-speedfrequency

I was upto use the UART of my Atmega8 but when i looked at the formula for UBBR, it asks F_CPU(frequency). I have made my own board and havent connected any external clock so what is the frequency my atmega8 runs on?

Further when i looked up to datasheet it says that it has upto 16Mhz, So am i running it on 16 Mhz or what?

Best Answer

Many AVRs (like ATmega8, ATmega16, ATmega32) have internal RC oscillator. It is calibrated for 1,2,4 or 8 MHz. It has +-3% accuracy. Frequency of oscillator gets affected by VCC and temperature. (source: http://www.elecrom.com/2007/10/15/configuring-avr-fuse-bits-for-clock-selection/ )

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