wonky eproms

David Griffith dave at 661.org
Sun Feb 4 08:40:44 CST 2018

I have a few tubes of ST-branded M27C256B UV-erasable EPROM chips.  All of 
these fail to program starting at 0x200 until 0x27F.  At 0x200, 0x00 is 
written, then until 0x27F, the bytes are 0xFF.  What would cause this? 
Can it be fixed by an extra-long time in the eraser?  Should I just break 
out the hammer?

At least I know the programmer is capable of programming a TI-branded 
27c256 and 29c256 flash chips.  Might there be a bug in the programming 

FWIW, I'm using a Minipro TL855.  Linux software is available at Github: 

David Griffith
dave at 661.org

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