Changing a few bytes of a 27c512 image.

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Jayfm

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I want to edit some data on a 27c512 image.

I can do it ok, but then the eprom cannot be used as it has an error? ...
So I am not sure how or why this happens.

Is it a Checksum? I just do not understand anything about checksums?


PLEASE help....frustrating
Thanks
Jay
 

The 27C512 is just a memory. It knows nothing of checksums. However the application circuit that you put the 27C512 into may very well require a checksum of some sort to work properly. There are many different checksum formulas. Unless you have some inside information on the thing that this chip gets plugged into, there is no way to tell what checksum, if any, is required. And even if you do determine the checksum formula, you would still have to be told or just know what available memory locations can be adjusted to achieve the needed checksum.
 

I realise it is "just a memory".....

I know what the device is that uses the data from the eprom too!

I guess it is an impossible task. The software used to write data to the eprom is at least 24 years old now, and it has several shortcomings.

Would looking at a new image without out any user data programmed onto it and another with some entries of data help in any way in determination of a checksum location?



Thanks for the reply anyway.
 

you can used hiew hex editor with lossing checksum

Fragrance
 

Thanks Fragrance, I tried it using your suggestion, but still an error once changed. May be I did not do it correctly, but it was saved with the changes I made, then burnt to the eprom. It has an error.


Any suggestions?


Jay
 

Jayfm said:
Thanks Fragrance, I tried it using your suggestion, but still an error once changed. May be I did not do it correctly, but it was saved with the changes I made, then burnt to the eprom. It has an error.


Any suggestions?


Jay
Click to expand...


Ok I have same issue couple of month back I have PIC hex file with startup logo on LCD and want to change the logo, when I made changes to welcome logo, I get big surprise that program stop working.
So what I did load the hex file in programmer edit it inside programmer then program the code back to PIC now this time its work
Try to edit the hex file in side programmer edit window that way may be your check sums never change.

Fragrance
 

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