Changes on IC´s

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I have program runnin on a AT90S1200, now I need to change the device for a AT90S1200A, the problem is that the program runs but much slower, I´d like to know what is the problem and how to correct it?

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AT90S1200 A runs on an internal RC oscillator with a nominal frequency of 1MHz (the 'A' means that this internal RC osc fuse is programmed from factory. If you have been running your 1200 on a different (higher) frequency before, this is why your application now runs slower.

Correct it by erasing the RC fuse in AT90S1200A (must be done using a highvoltage paralell programmer, eg STK500.

bjorn

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I can't remember the details, but the at90s1200a (or any "a" part for that matter) uses an internal 1MHz oscillator as a factory default. You will have to set a register to use the external clock. Try looking it up in the spec.