Dang! That Z80 computer looks AWESOME. Is there a website that talks about it?
Is this a homebrew project or something he plans to make available as a kit?
73 Eugene W2HX
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-Original Message-
From: cctalk On Behalf Of Eric Smith via cctalk
Sent: Wednesday, April 27, 2022 12:00 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: new Z80 monitor ROM works with no RAM
I wrote a new monitor ROM for the Z80, called umonz, which can provide some
basic monitor functionality even if there is no working RAM. In other words, it
doesn't use a stack or store any variables in RAM. It supports reading and
writing memory, I/O ports, and loading and dumping Intel hex format.
https://github.com/brouhaha/umonz
It's tricky to write any non-trivial Z80 code without a stack. I used IX and IY
as subroutine return address registers, allowing two levels of subroutines,
though a subroutine that uses IX can't call another subroutine using IX, and
similarly for IY.
The background is that John Doran built a custom Z80 (equivalent) computer
system which he calls the Z80/M. It doesn't use an actual Z80 CPU; there is an
Altera (now Intel) MAX 10 FPGA on the control panel board, and a Z80-equivalent
core, along with the front panel logic, is in the FPGA.
There is a 16-slot expansion bus using 96-pin DIN 41612 connectors. The cards
are Eurocard 3U x 220mm.
https://www.flickr.com/photos/_brouhaha_/52032832163/in/album-72177720298429134/
There's an expansion card that provides 512K of flash, 512K of SRAM, page
mapping, a Z80 SIO for two serial ports, and a CF card, all compatible with the
equivalent RC2014 cards.
He expected that ROMWBW and CP/M or ZSystem would "just work". However we had
to track down several minor hardware design issues to get it to work.
After writing a few simple one-off test programs, I got tired of the assemble,
sneakernet, program flash chip, test in target loop, so I decided to write a
monitor. That definitely sped up the debug process.