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P87C51 replacement

Question asked by Nigel Hale on Jan 12, 2018

I am looking for a replacement for the now obsolete P87C51SBAA,512 processor.

I have fitted the second generation P87C51MC2BA/02,529 device, programmed with the same .hex file as used for the old part.

I notice in the data sheet for the new part that it runs instructions at twice the speed of the old part

The critical timings in our application make use of Timer 1 so I did not expect them to change.

However, I find that these timings have halved when the code is run in the new part.

Is this because the internal clock runs at twice the speed, resulting in timer time-out periods also being halved?