Sinclair ZX80 / ZX81 / Z88 Forums

In my latest project (porting a ZX81 m/l program to the Lambda) ... I'm working out how to modify the keyboard handling. Do all the 8300 variants use the same keyboard layout?

wikipedia photo

It appears to be based on the same 5-column by 8-row matrix that the ZX81 uses, with these differences:
* extra SHIFT key to the right of SPACE
* RESET key to right of 0

The EightyOne emulator shows two different keyboards
* the below when using the standard setting of Lambda.rom
* ZX81 keyboard when using 8300.rom this matches the wikipedia photo less the two extra keys

The keyboard
There is 1 keyboard for the Lambda 8300. The two shift keys are eletrically connected together.

The reset key, is the only "extra" key. However it is not connected to the keyboard matrix, but just connected the reset pin on the CPU to ground.

Regarding the 8300.rom
Many bought the Lambda 8300 because it had a better keyboard than the ZX81. It had joystick port, and sound. However not beeing as popular as the ZX81, there was no software.

Fred Nachbaur took the ZX81 ROM, and modified it, so it would run on the Lambda 8300, as there are some hardware differences. This is the 8300.rom. So people with the Lambda 8300 now could use most of the ZX81 software. It is now fully machine code compatible. Litmits are: Hires graphics will not work, as the ULA on the Lambda 8300 is quite different. The charset on the Lambda 8300 remains.

So when EigthyOne changes the picture for the keyboard when using the 8300.rom, it's just to help you, as now the EightyOne is emulating a Lambda 8300 with a ZX81 customized ROM. However the 8300.rom makes most sense if you have the real hardware.

https://airtable.com/shrXP65XwdIFSDVn3/ ... m0E6TGjA3O

Thank you

The ROM information is much appreciated, and answers many questions