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Re: [avr-gcc-list] Determine CPU clock frequency
From: |
Joerg Wunsch |
Subject: |
Re: [avr-gcc-list] Determine CPU clock frequency |
Date: |
Mon, 13 Mar 2006 11:59:38 +0100 (MET) |
(Please use a subject line! Please don't send HTML mails.)
"Gary Taylor" <address@hidden> wrote:
> Does anyone have a way (in firmware) to determine what crystal is
> connect= ed to a ATmega128 ? I have 2 x different versions of
> product in the field with 2 x different = crystal values, and need
> to main the same code in both versions.
You need some reference in order to do this. If you've got a 32 kHz
async crystal attached, that would of course be the easiest way.
If both clocks differ very much, you could perhaps try to use the
EEPROM write timing as a reference. The EEPROM is specified to use
8448 cycles of the 1 MHz RC oscillator for a write operation.
Finally, there's the obvious thing to do: if you've got two differen
hardware revisions, use two different hardware IDs (like through pin
strapping, or through some kind of serial number).
--
J"org Wunsch Unix support engineer
address@hidden http://www.interface-systems.de/~j/