Just because it works on the 'test board' and it doesn't work on the 'wirewrap board', doesn't mean you schematic/parts are correct for that particular application.Originally Posted by menta
I don't see any capacitors across Vdd/Vss on the 'test board', but that doesn't mean there aren't any there (i.e. stray capacitance).
I see a single resistor leading over to MCLR, but no capacitor, again, doesn't mean there isn't any capacitance on MCLR (albiet stray caps). And it also doesn't specifically mean that you have to have a capacitor across MCLR to ground, but it sure doesn't hurt.
It also doesn't mean that your wiring, no matter how many times you've checked it, is correct and without fault.
It also doesn't mean that the program you wrote for your '877 is actually going to run on your '887, or the other way around, without any changes in the source at all. the 16F877A is an old chip, the 16F887 is a new chip. A lot of differences between the 2.
Maybe your programmer's power supply is a lot smoother than the other power supply you're using.
Maybe your other power supply can't handle the extra load and dumps causing a reset, maybe it doesn't come up fast enough to satisfy the PIC, maybe it comes up too fast.
1650 different reasons why stuff don't work. I think we've isolated like 3 possibilities...
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