How do you know EEPROM chips are good


Joined Apr 28, 2012
There's still a lot of equipment using them. I have quite a few pieces of equipment from the 70's that are still quite useful. If the EPROMs lost their data, that equipment would be useless.

Many auto and motorcycle owners would agree that they're still useful and required. My "old" BMW wouldn't run without a 27C256...
yes correct but they also changed to flash, often plcc, todays often serial.

i burned firmwares on 2 small eproms a customer requested it, used a g540 on refurbished eproms, no problems.


Joined Dec 29, 2010
There was some circuit boards I have found in my past that have "Inverted the EEPROM code" and used Logic IC chips with inverted inputs or outputs that is why they inverted the code in the EEPROM chips.

The schematics didn't use the inverted logic chips , but the repair person swapped them out and used inverted logic chips which the repair person inverted the EEPROM chip.

How do you invert the EEPROM file code? so the starting address is the ending address
Invert the ROM contents
Invert the ROM entries
The only reason I can think of, is that the author of the software wanted to protect his/her IP. He can either swap addresses lines of the code or bit pattern eg swapping bit 2 with bit 5 and bit 7 with bit 1. My eprom programmer software from Needham was able to play this sort of stunts before programming the final data onto an 27Cxxx eprom.

So dumping the eprom from an Z80 board ROM doesnt disassembled like Z80 codes at all. Not sure if you can do that with the codes in the internal code memories of a PIC uC.

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