Hello to all I had Copied (For future Backup Purpose)One EPROM (In one of the Industrial Electronic Module )with Checksum using the EPROM Reader . After reading the EPROM I put it back in the Module. It is not working.I later note that the EPROM (27C512)had first 128 Lines reserved for Application Program + Checksum for Configuring the Module Operation) balance up to 8 K for Firmware of the Module )Anybody explain why it happen . How I can recover it and make the module Function again . Please reply Thank you
Just READING an EPROM, by definition, can not change the contents. Did you do anything else to it, that you have have forgotten to mention? Have you tried burning another copy from the image you stored?
On May 7, 2:37=EF=BF=BDpm, snipped-for-privacy@rediffmail.com wrote: How I can recover it and make the module
I'm not sure I understand, because if you copied an EPROM, regardless of what the actual bytes were to be used for, the copy should be identical to the source.
IF however you copied the contents without regard to any required offset start address (or similar, etc..), and then copied the file to some other starting address, then I can see where that would cause a problem. However, in that case, the checksum should fail because it is generated in part using the address.
Perhaps the checksum did not fail because you are on a page boundary, or ??
To fix it, I guess you could try loading the file to a new (separate) EPROM using 128x8 as the offset start address and see if that does it. You'll have to check the documentation on your programmer on how to do this. Many can correct the checksums on the fly.
If the original read was wrong (offset problem, etc..) you should still have all the data, but the start addresses and checksums will all be incorrect. You'll have to strip these, insert the correct start addresses, and then calculate the new checksums.
There are utlilties available for this. Avocet had a real nice one, and if you truly get stuck, maybe I can get you a copy. (It's from the mid '80's so I doubt they'd complain too much?)
Finally, I should mention that it is possible on some hardware to "read" correctly, but not "write" the same part. (For parts where the EPROM read and write voltages differ.) If that is the case, your original read is probably fine, but you clobbered the device when you re-wrote the file back to the device. Double check the EPROM Manuf & part# and make sure your EPROM programmer is actually set to the job at hand. Most good device programmers would give you a write error, but some won't.
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