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Re: [avr-gcc-list] prescaler

From: Michael Tsao
Subject: Re: [avr-gcc-list] prescaler
Date: Wed, 12 Jun 2002 13:28:53 -0700

    Can someone help me by explain what the prescaler is for when
using the timer function? I know it is remedial for most of you but I
really am having trouble finding good info on this. thanks B

You might not want your timer to count as fast as your avr is going. If you have an 8MHz chip, an 8-bit timer set to a 1:1 timer/system clock ratio will overflow in 0.000004 seconds (assuming exactly 8 million cycles per second), and for many applications that's uselessly short.

So the prescaler says "make the timer tick only every X system cycles."

E.g., if you have it set to system clock/1024, then it ticks only every 1024th system cycle. On an 8MHz chip, an 8-bit timer will overflow in 0.032768 seconds (256 * 1024 * 1 / 8000000). Still short, but at least that's milliseconds.

Basically you trade timer resolution for timer lifespan.

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