Hi Victor,

if you need 4 interrupt inputs, you can also use the 4 capture inputs of the 80C552. Additional you can select, if the falling or the rising edge generate the interrupt. If you need only the interrupt you can still ignore the captured value.
Please look at the data sheet, how you can enter the capture mode.
I self never used the 552.

I would prefer using 2 micros (AT89C1051 = small and cheap) to do this task. Or 4 micros to avoid long wires and place every near by each wheel.


Peter