Help with EPROM Programming (27C400)

[mbarszcz]

I'm trying to burn some 27C400 EPROMs on a TL866II with one of the gglabs adapters, and whenever I try to burn the EPROMs (AAAA in this example), this is what I get back, a repeating pattern of zeroes every few lines:



I have tried various jumper/dip switch settings and double checked everything, and it all seems fine.  I also ordered some new EPROMs from a different seller in case they were counterfeit, but the results did not change.

The schematic for the design is here: https://gglabs.us/sites/gglabs.us/files/e2r16-b01_sch.pdf

All the address and data lines are just traces to adapt the 4096 pinouts to the 27C400, so I can't see how they wouldn't be working.

The rest of the circuitry is just dealing with the VPP and select lines, so I can't see how that would cause a repeating pattern of zeros to be programmed.

Any ideas?

[amyk]

I would first determine whether it's the actual programming that didn't work, or the readback, by manually wiring the chip with the appropriate bad addresses and probe the data lines to see what the values are.

Either way, the pattern suggests what to look for on the address lines:
80-9F  =    00100xxxxx
180-19F = 01100xxxxx
280-29F = 10100xxxxx
380-39F = 11100xxxxx
...

Using a logic analyser or scope, you can see if A5-A7 correctly take on the values 0,0,1 respectively.