eprom questions

snapJaw

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This week - I'm getting an eprom burner. (GQ-4X)

I have several boards with suspected bad roms, and I hope to fix a few, in addition to burning some bios roms, etc.

The one set of roms I can't seem to find any information on is for a bobble bobble (bootleg) board with some bad sprites. The roms are TMM24512P - and I can't seem to find any info on them. They don't have the window on top - so I would assume they can't be re-written?

Do eproms cross reference to other usable eproms? I've looked around, but can't seem to find some of this basic info. Most of the other roms I've found plenty of info about.

Thanks in advance!
 
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Those are burn once roms or PROMs, internally they are the same as an eprom but the quartz window was such a large % of the cost that the market demanded a write once option so yes you can't erase them. The will be compatible with 27512s tho!

I struggled to find a full list but the clue is in the 1st number,

23 - mask rom - contents are etched into the fabric of the chip as it is made.
24 - PROM - what you have
27 - EPROM
 
Also note that there exist 27xxx "EPROM" chips that do not have the quartz window. They were write-once versions of normal EPROMs, cost reduced by putting them in an opaque plastic package.

-Ian
 
Also note that there exist 27xxx "EPROM" chips that do not have the quartz window. They were write-once versions of normal EPROMs, cost reduced by putting them in an opaque plastic package.

-Ian

These are called "OTP" ROMs... One Time Programmable.
 
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