Can't make RA1 a digital Input on (10 out of 20) 16F887.

[HenrikOlsson]

Hi,
So, it's not only the PIC that differs on the ones that doesn't work, you are changing the whole board, including the PIC, correct?
I think that since it works on some PICs (or boards rather, if that's the case) the code is likely not the fault. Had it been a faulty register setting it wouldn't have worked on any of them - but I've been wrong before....

What's the supply voltage of the PIC (5V?) and what voltage levels are present at RA1 with the switch in either location?

You say that you ground the pin to "make" the signal, is it possible that there are TWO (or more) grounds in your system and that they aren't connected. When you measure the voltage you reference the "correct" ground which, for whatever reason, isn't connected to PICs ground so it doesn't see the voltage that your DVM does?

I'm pretty sure it's not RMW, especially so since your two outputs are on different ports. A Read Modify Write issue usually presents itself when you're trying to do several consecutive bit operations on a single port.

I'm leaning towards a hardware issue of some sort though it IS strange that it works with "any other pin except RA1".... doesn't make sense but things usually doesn't untill you find the real reason.

/Henrik.

[towlerg]

The PIC's are "soldered in" on all the boards you have?

All the boards are from the same batch?

All the PIC's are from the same batch and silicon rev.?


George