write eprom error T48 programmer

[geezbill]

I have a few AMD 27C256 eproms. In the programmer i can read them and write back the bin saved from them but i cannot write a bin that i need to for a piece of gear i'm trying to get running. Again, i hav no issues reading and writing the eprom contents back to the eprom but i cannot write the bin i'm working with. Any ideas? Many will chime in about voltages but that can't be the issue as the reading/writing of the eprom works just not with a particular bin.

[wraper]

It's not electrically erasable. It either can be erased by UV light if has a quartz glass window, or it's an OTP EPROM if there is no window, and cannot be erased at all.

[geezbill]

so it must be erased first? i have the blank check unchecked

[wraper]

so it must be erased first?

yes, if it's the type that can be erased to begin with.

[xvr]

so it must be erased first?

Yes, and you have to use special hardware for this. Just a programmer is not enough.

[geezbill]

ok i ordered a UV eraser

[KG7AMV]

Just a reminder there are some 27C256 that are (OTP) one time programmable no window to UV erase them.

[geezbill]

these have windows

[CaptDon]

How have you ever had any luck writing to one of these devices if it wasn't blank or at least the area you were writing to was blank? When UV erased it is all 1's, FF, FF, FF etc. The one time programmable devices have no window and usually carry an 'R' suffix, 27C256R as an example. Make sure the UV eraser has a conductive 'black foam' pad to rest the I.C.'s on inside the eraser. Without the anti-static 'bug rug' the I.C. can develop some weird internal voltages between pins and be damaged.