willem 27c128 reading error

[djsolohf]

Hi.

I read a 27c128 by mistake with the willem programmer set to read 27c256.

The resulting file is rubish. Is there any way of restoring the original file?

Thank you

 

[ZASto]

set the programmer to 27c128 and re read the chip.

You can not damage the EPROM only by reading it the wrong way

 

[djsolohf]

Hi.

I wish i could but the problem is that i don't have the original eprom anymore.

I was about to write a new one from the file and i realized that the file was 32kb and should be 16kb.

I write the file in a 27c256 but the result is rubish.

I'm wondering if reading the 27c256 with the settings for 27c128 may reverse the process ..... i don't know but i'll give a try tonight.

Thank You.

 

[ZASto]

Nope

 

[betwixt]

If you read a 128K chip as a 256K one, all it does is ignore the most significant address bit and read the same contents twice.

If your file is a binary one, it should still work, just tell the programmer you are using a 128K bit device and it should stop reading when it gets half way through the file. If you have an Intel Hex file, try reading it in as a 256Kbit file then re-save it as a 128K bit one.

Brian.

 

[FvM]

Pin A14 at 27C256 is nPGM at 27C128. Setting it low disables data read. Thus the upper half of your file should contain the correct data.
Just specify an offset when loading the data in your programmer.

 

[djsolohf]

Hi.

I already tried to use only half of the file but the two parts are rubish.

betwixt how can i read the file and save it with different size?

Thank you

 

[FvM]

the two parts are rubish

Then something else apparently went wrong. What do you expect from reading rubbish and writing it with a different size?
(Assuming you actually verified the file content is meaningless).

 

[djsolohf]

Hi

Fvm you are right i think there is nothing to do but i was hoping that i could recompress the file again to its original size.

Regards.

 

[betwixt]

You can't recompress the file, it isn't compressed at the moment.

You don't mention what format your data is in so I'm assuming it is raw binary. If it isn't you should be able to convert it to raw binary easily.

The file should contain one byte per location in the 27C256 so it's length should be 32K (32768 bytes). You want to use 16K of that, starting from half way up, in other words the block from 16K to 32K, ignoring the part from 0 to 16K.

If your software lets you specify the addresses to program, all you have to do is tell it to use the top half of the data. If that isn't possible, try telling it to save the top half as a new file and then load it in as data for a 27C128.

Brian.

 

[djsolohf]

Yes, the file is in raw binary but the problem is that i checked all the file and is useless.

Asuming that reading a 27c128 with the jumpers on the willem and the software set to read 27c256 should produce a file with double the size but real data on the upper half of the file i think that perhaps my file get corrupted after the reading.

I'll try to repeat the procedure with another 27c128 to be sure.

Thank you.