Thank you very much for your answers.
The problem solved by itself and I was able to debug my program and go
further with the development. Now I have another problem: a 4x5 matrix
keyboard is interfaced to ports A0-A4 (the rows) and when I energize
column 5 (A4) on the PIC 16F628, the keys from the 5th row won't read...
I've read on the datasheet that pin RA4 is open drain, unlike the other
RA pins, which are CMOS. I don't know the differences between those two,
and if this is the cause of the row not functioning. I've debugged the
program so I think the code is correct. Also the hardware...
Could you please give an oppinion ?
Thank you for your time.

Lucian

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