skx / z80retroshield Goto Github PK

I should port the BASIC interpreter over as an example.

This is more complex than the other examples:

• It uses in (0),a and out (0),a for serial I/O.
• It uses in (1),a and out (1),a for setup of serial-port.
  *This can probably go away.
• It uses an interrupt to signal new input is ready.
  • RST 38 called via IMM 1
  • If in (1),a & 0x02 then fetch a character.

So either the interrupt routine needs to be handled differently, as a timer, to poll, or I need to export new CPU primitive for raising/clearing the NMI pin.

Hi,

I got a Z80 Retro Shield and was looking for a good sample and found your project.
I was able to get BASIC working right away. Very useful project.
Thank you very much.

Next I ran your project on an AT SAMD51 (Cortex M4 120MHz) board instead of an AT Mega 2560.
It ran fast.

My working branch on my github includes these changes below,
https://github.com/hanyazou/z80retroshield/commits/adafruit-grand-central-samd51

• Support for the Adafruit Grand Central M4 board
  https://learn.adafruit.com/adafruit-grand-central
• Added debug output
• Faster operation (the speed_test says 1,263K cycles per second)
• Simple and tiny bug fixes

If you are interested in this fix I would like to send you a PR.
Please take a look at my branch.

Best regards.

12:43:52.226 -> Z80 configured to run endless stream of NOPs.
12:43:52.226 -> Cycle/Second will be dumped once per second.
12:43:52.226 -> Cycles per second second:63
12:43:52.991 -> Cycles per second second:1262937
12:43:54.019 -> Cycles per second second:1263436
12:43:55.020 -> Cycles per second second:1263236
12:43:56.016 -> Cycles per second second:1263336
12:43:56.997 -> Cycles per second second:1263436

For neatness we should:

• Rename ram_read to memory_read.
• Rename ram_write to memory_write.

Leave the old names for compatibility though. Sigh.

I found a FORTH implementation for a Z80 system here:

• https://github.com/rachel8973/RC2014-FORTH

However it assumes that there is a lot more RAM than available; the driver is essentially the same as that used in our BASIC example - so porting it should be trivial - I've ordered some SPI FLASH-RAM which will allow me to access 64k of RAM, however the downside will be that such external RAM will be mandatory.

Still it will be a good "big" example to add.