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ROM upgrade
Posted: Fri Jul 29, 2022 5:43 pm
by Creator
I see the ROM upgrade for ZX80 is a change from 4K to 8K but both are in a 24 pin package. Classically 8K x 8 chips are in a 28 pin package. How is this, or better what have I misunderstood here ?
Re: ROM upgrade
Posted: Fri Jul 29, 2022 5:53 pm
by Moggy
The upgrade ROM is just the one found in the ZX81.
The chip pinouts can be found here..
viewtopic.php?t=1249
Data sheet here...
https://pdf1.alldatasheet.com/datasheet ... D2364.html
Re: ROM upgrade
Posted: Fri Jul 29, 2022 6:52 pm
by 1024MAK
Creator wrote: ↑Fri Jul 29, 2022 5:43 pm
I see the ROM upgrade for ZX80 is a change from 4K to 8K but both are in a 24 pin package. Classically 8K x 8 chips are in a 28 pin package. How is this, or better what have I misunderstood here ?
EPROMs use a 28 pin package, but mask ROM chips (needing less control and supply inputs) can use 24 pin packages.
Mark
Re: ROM upgrade
Posted: Fri Jul 29, 2022 7:48 pm
by Creator
Yep, should have realized that. I'm thinking ahead to burning upgrade ROM code but I see that's not going to be easy