Hi,

I'm working with a software clock routine where I want to be able to detect
whenever a second have passed.
I'm using an AVR with a 4.194304 MHz crystal. I am using the prescaler which
divides the clock signal by 1024. I use the TCNT0 to get further division of
256. In the timer interrupt routine I use a register to count from 0 to 16
to get to a point in the software every second.

4194304*(1/1024)*(1/256)*(1/16)=1

This software clock seems to be a bit fast so the displayed seconds do step
remarkably (about 1.1x ... 1.4x ) faster than it should normally do.

If I suppose that my crystal is a 30 ppm one so it shouldn't accumulate such
a big error.

Plese give my your input on this issue since I'm quite frustrated.

Laszlo Cser