Hi,

You had to install the "Car_zx81.bin" or "Car_zx81.s3f" ROM at 8192 (2000h) and run the P file.

This card is an UDG feature and can't be used to draw HRG screen.
You can retrieve 7 different characters set, but you can't make your owne charset anyway.
You had to reprogram an EEprom or use a different ROM to redefine it!

This card just redirect the Ir register to another address to point to the ROM binary characters table.
IR is set to 1Eh in the ZX81's ROM. But this register can point to another address.
The IR register active the /ROMCS and read the pointed byte...
This feature can't be used in the RAM (shadow or high memory), the Ram is refreshed by the /RAMCS ... not the /ROMCS.
You had to change the RAM refresh mode to get something.
However, all chars will be Blank (nothing at screen) or a reversed block if it's a reversed character.
You can't make UDG with a 64 Memotech ram pack...

But, on emulators, the /ROMCS equal the /RAMCS memory call.
The CPU don't choose beatween ROM or RAM ... and allow to point IR to the RAM.

Thanks to Partice how dump his Dktronic Eprom.

Note:
 This ROM was allready available in the "Eighty-one" emulator(ROMS folder), and is the same binary file.

Have Fun!

XavSnap.