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Why isn't my processor running as fast as it should? I'm writing some code in assembler and pulsing an IO pin as such.

sbi 0x18, 0;
cbi 0x18, 0;

Which should produce a pulse two clock widths wide. The processor is set to be running at 8Mhz so how come the pulse width is 2uS? It should be more like 0.25uS.

I take a really close look at the data sheet and notice a clk/8 option, then I check out the "Fuse" section of the AVR Studio program dialogue and see this.

Notice anything in the screen grab (hint, the red circle might help)?

The internal fuses are set to divide the oscillator clock frequency by 8.

Doh!

 


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