ZXpand on ZX80 without ROM swap

General Chit Chat about Sinclair Computers and their Clones
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anightin
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Joined: Thu Sep 05, 2019 10:35 am

ZXpand on ZX80 without ROM swap

Post by anightin »

Dear All,

Thanks to SirMorris I now have the ability to plug and play with my Zxpand+ and my ZX80. This way I can keep my existing ZX80 ROM in place and use the machine as stock when Zxpand+ is not plugged in.

This was made possible by enabling a similar ROM deselect mechanism that the ZX81 has, and hence allows the overlay ROM on the ZXPand+ card to be used.

The mod for the ZX80 is here and requires the cutting of the CS1 line from IC6, replacing it with a resistor, and then running a CS line from pin 23B on the edge connector on the ROM side of the resistor.
zx80-sch_CS.gif
Here is the mod on my ZX80:
IMG_7384.jpeg
Here are the results: :D
IMG_7391.jpeg
IMG_7392.jpeg

Work done on the ZXpand:
  • Re-flash the ZXpand overlay EPROM with ZX80 modified version -- from the Wiki
  • New CPLD image loaded via SD-Card. This image does not disable the overlay ROM as the current ZX80 one does -- Direct from SirMorris
Note: Please be aware that any mods to your ZX80 are done at your own risk :shock:

Best wishes

Andy
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