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M27C256B EPROMs and Minipro TL866 trouble

tl866 eprom minipro

3 replies to this topic

#1 Frotz OFFLINE  


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Posted Tue Feb 13, 2018 2:26 AM

I have 15 ST-branded M27C256B UV-erasable EPROMs and a Minipro TL866 chip programmer.  The chips came as used off Ebay.  When I try to program these chips, I get this:

$ minipro -p "M27C256B @DIP28" -w cleurom2.bin -S
Found Minipro TL866A v03.2.80
Chip ID OK: 0x208d
Writing Code... OK
Reading Code... OK
Verification failed at 0x200: 0xc8 != 0x00

I thought that this was due to this particular variation of the 27c256 requiring more current than the Minipro burner could provide.  So I bought a cable that has two male USB type A plugs on one end and a female type A jack on the other end.  I've used variants of this for older hard drive enclosures that needed the extra current.  This didn't help in the slightest.  All of them fail programming in exactly the same way.  Erasure goes fine.  I've programmed several 27c256 chips from Texas Instruments with no problems.  What's going on here?  Am I better off simply trashing these chips?



    River Patroller

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Posted Tue Feb 13, 2018 7:00 AM

Your mention of concerns about current prompts me to mention that I have a TL866 that I bought primarily to test TTL logic chips. I was having trouble with one particular type of logic reading as faulty when manual testing proved otherwise. I ended up running one pin through a buffer chip between the TL866 and the chip under test and the problem went away. Other types of chip tested fine using that same pin. I can't remember exact details about which types did and didn't have a problem.


I theorize that the transistor driving that TL866 pin is out of spec, but haven't bothered to try to replace it yet. Maybe you have something similar going on?

#3 Frotz OFFLINE  


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Posted Wed Mar 7, 2018 3:04 AM

Would anyone with a known good programmer other than a TL866 (preferably something from the 1980s or 1990s) like to play with one of these questionable EPROMs?  I'd like to get to the bottom of this problem and hopefully rule out bugs in the TL866 or the controlling software (https://github.com/vdudouyt/minipro).




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Posted Wed Mar 7, 2018 7:27 PM

Sure, I can test one for you.  I am in CA, so shipping is no biggy.  I have very expensive programmers, that program thousands of chips.  I program 27C256B's all the time.

Also tagged with one or more of these keywords: tl866, eprom, minipro

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