To run CPM now that I upgraded the SRAM from 32k to 56k I need to add a compact flash and the SIO/1 to the computer, the thing is, I never though about this when a made my first Z80 board but at lease I have a 40 PINs expansion ports to help me.
First thing first, I want to run Grant Searle’s CPM version since I don’t know how to program I assembly to make it work on a other board design. I’d started with the SIO/1, Grant’s version is using a SIO/2 so I just need to adjust the pin out since they are different but it should not be an issue.
I put the SIO/1 and the glue logic for the memory address and I/O decoding on the breadboard and connected everything together. Note, I used the Data PINs from the removed MC68B50 to limit the length needed to reach the Compact flash.
I was able to boot into the ROM monitor and launch Basic with no issue, so I used Grant’s monitor to load the hex’s files and install CPM on the Compact flash but when I tried to launch CPM the computer froze completely. After much troubleshooting the issue seem to be with the data bus signaling being to degraded at the Compact flash or something with the memory decoding.
Dom's Electronics Projects 