BUT, if the shop told you "the chip needs replacing" (which I'm really skeptical of to begin with) that would imply that the chip is bad, right? And if the chip is bad, how can you read the program off of it?
One company I had dealings with some years ago lost the code files to one of their old PIC projects, but had some of the flash code-protected working chips. They shipped it to a Chinese firm which extracted the code for about $US150. So it can be done at a price. They only required one working chip to do the extraction.
PICs, even 'old' ones like the 16F57 are quite hard to damage so I too am skeptical about it being the cause of failure.
However, if they are dead and you have one surviving one, it doesn't necessarily mean you can make copies of it to replace them. Almost all PICs have a copy protection mechanism in them which allows them to be verified after programming without reading the real data back. There is no obligation to use copy protection but almost every manufacturer uses it to prevent their software being copied. The only way to find out is to read the good PIC and see if what it contains makes sense when disassembled.
It would be interesting to see if the bad PICs still contain good code, they may have failed by damage to the pins while the core inside is still workling perfectly.
Brian.
The 'F' in the PIC type tells us it uses Flash memory so it can be erased and reprogrammed. Erasing does just that, it wipes the exitisting memory and also the protection bit so it can be used as though it was brand new. However, the existing program probably can't be read from a protected device, there are companies that claim to be able to do it but they give no guarantee and they are expensive. They don't use conventional programming tools, they have special forensic methods for reading the memory, including in some cases actually dissolving the IC body away so the fuse bit can be directly targetted.
I still think it odd that water would damage the PIC though. It isn't impossible of course, the most likely cause would be water in the PSU circuits zapping it with too much voltage. I would have to see one of the units to be sure. Is the PIC in a socket or is it soldered to the PCB?
Brian.
Hi Brian, I think the chip is in a socket. The repair shop I used repairs TV's and all sorts of electronics at component level. She says she is certain the chip needs replacing. If you'd like a look at one let me know. I'm willing to pay to get this sorted. Will photo's help of the circuit board help? Let me know.
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