[ECOS] Re: Time problem: Clock running slow

Iris Lindner ilindner@logopak.de
Fri Sep 3 14:21:00 GMT 2010


Hi everyone,
thanks very much for the comments (and sorry for not answering every 
question)!
Meanwhile we found the reason. =) Special thanks to Frank.

@ John:
Yes, we use a crystal (Dallas-chip) RTC which works fine. When I query it 
directly for getting the current time it is always correct (no delay after 
many hours). But since access is (too) slow (I2C) we use that 
mentioned "trick"...

So the problem must have been on the target.. It was a wrong CPU I/O bus 
speed, it is not 266 but 264 MHz. Since this value is used for calculating 
the real-time clock period we got 66500 instead of 66000. This was exactly 
the range of the time drift.
So everything was fine with interrupts.

(The timer should be a bit more precise since our machines can have uptimes of 
months or more - and that delay would lead to an error of nearly 2,5 days per 
year.)

Thanks again!
cu
Iris


-- 
Iris Lindner
Software Development

Industrial Print and Apply Labelling

www.Logopak.com

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