ZXpand on ZX80 without ROM swap

anightin · Post by **anightin** » Fri Jul 17, 2020 12:37 pm

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.

Here is the mod on my ZX80:

Here are the results:

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

Best wishes

Andy