ROM upgrade

Discussion about ZX80 / ZX81 Software
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Creator
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Joined: Wed Jul 27, 2022 3:11 am

ROM upgrade

Post 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 ?
Moggy
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Re: ROM upgrade

Post 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
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1024MAK
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Re: ROM upgrade

Post 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.

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Creator
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Re: ROM upgrade

Post 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
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