A Pico MZ-80A ?

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When I set out to create the Pico MZ-80K, I swore that I’d only attempt to emulate the Sharp MZ-80K and not the whole MZ range.

A Pimoroni VGA Demo Base and Raspberry Pi Pico 2 - supported hardware for the Pico MZ-80K. How hard can it be to support the MZ-80A as well?!
A Pimoroni VGA Demo Base and Raspberry Pi Pico 2 – supported hardware for the Pico MZ-80K. How hard can it be to emulate the MZ-80A as well?!

But it is very tempting to extend the code I have to cover the MZ-80A as well. There’s not a lot of difference between the two machines (far less than say jumping from the MZ-80K straight to the MZ-700). It’s also relatively rare in the wild these days compared to some of the others in the range. So definitely worth preserving.

And it’s still winter … far too cold outside to go gnuing.

These are the differences I’ve identified so far:

  • Green on black display rather than white on black, plus reverse video as standard.
  • Different monitor (SA-1510) and CGROM (display to ASCII code conversions are subtly different to those of the MZ-80K).
  • GRPH key, rather than the blue keys for graphics (keyboard layout has a numeric keypad instead).
  • Double sized VRAM that supports scrolling (software configurable).
  • Optional user ROM at 0xE800 – 0xEFFF that is executed if present at switch on.
  • Reset key (moves monitor back to 0x0000 and allows a warm start, so not as simple as pressing the RUN key on the Pico’s carrier board).
  • The monitor can be swapped out from 0x0000 – 0x0FFF to 0xC000 – 0xCFFF. This makes CP/M a possibility if coupled with an 80 column mod using the double VRAM space plus revised monitor ROM. I’d have to wade back into the realms of the Sharp floppy disk implementation to achieve this – pretty tough going.

Hmm.

How hard can it be?!