Switching out EPROM chip

Using, learning, programming and modding the Gigatron and anything related.
Forum rules
Be nice.
Post Reply
Posts: 25
Joined: 14 May 2018, 09:04

Switching out EPROM chip

Post by Cwiiis » 19 May 2018, 18:41

I got my hands on a couple of NEC D27C1024D-15 chips that I thought would be compatible - Erasing them was fine, but I couldn't program them reliably above 4V (and as one might expect, reading back at above 4V also results in unreliable readings). Both chips I think are pretty old, is this a case of the chips just being knackered or are they not the right spec?

I'm using the TL866-II to program them, the closest thing it has is the NEC D27C1024A, but the default reading/writing voltages don't work (reading at 5V is unreliable, even on an erased chip, and writing fails out at anything above 4V) - searching around, I see there are a few A-variant chips, but I can't find any datasheets for any of them to know what that last letter signifies...

Has anyone else experienced anything like this, or has any advice? I'm thinking I'll just try another 27C1024 chip, but it'd be great if I could get these ones working too.

Mostly doing this for faster turn-around when running code, I've hacked up a ROM that just loads a picture (for aesthetics :)) and the loader straight away rather than the menu - still handy for emulation too: https://www.dropbox.com/s/t1sn5lni5810s ... 2.rom?dl=0

Posts: 2
Joined: 06 Oct 2018, 19:27

Re: Switching out EPROM chip

Post by pepperm » 24 Oct 2018, 10:17

I have the same problem with those chips, the NEC ones, with the same programmer. I can read the chip with the NEC option but programming fails, even when I turn the chip ID function off. I read somewhere about some success that someone had had by elevating the programming voltage to 13.5V but that doesn't work for me.

Did you get anywhere with your programming efforts?


Post Reply