COMX-35: Part 3 (Keyboard & BASIC ROMs)
8I downloaded the Emma 02 emulator which comes with a bunch of ROMs and COMX software. I noticed it included three newer versions of BASIC.
The HN613128 PROM with BASIC v1.00 is pin-compatible with the 27C128 so I removed the original ROM and soldered in a socket. I then tried all three versions ... v1.01, v1.02 and v1.03 ... but the COMX didn't like any of them. Putting the original PROM back in worked fine.
So a puzzle to be solved. The HN613128 data sheet does state that the active level of CS and OE1/OE2 are selectable by the user, so perhaps they are the inverse of the 27C128 (active high instead of active low)? Maybe that is the problem.
I did some work on the keyboard - I noticed one of the wires in the ribbon connecting keyboard to computer was broken, hence why some keys weren't working. I decided to just remove the inflexible & brittle ribbon cable and replace it with some pin headers on the mother board to allow the keyboard to be easily disconnected in future.
Now, it seems all the keys are working ... but something still not right ... S gives K, K gives K, Q gives I ... so still a bit more trouble shooting is required.
The Emma 02 emulator will also re-generate the audio for tape software from the .comx files, so I'll be trying to capture that audio onto a real tape ... once I get the keyboard working.
Gerben, a retro collector and original COMX-35 user - he has a few videos of the COMX-35, the COMX-PC1 and peripherals:
https://www.youtube.com/channel/UC7JTXr20RnsMQzQriKy-8cQ
Emma 02 emulator for CDP1802 systems (BASIC ROMs & software):
https://emma02.hobby-site.com/
COMX-35 software archive:
https://archive.org/details/comx-35roms
COMIX-35 homebrew clone:
https://github.com/schlae/comix-35
And various home brew projects using the RCA 1802:
http://www.sunrise-ev.com/1802.htm
Discussion forum on the 1802 processor (and COMX-35):
https://groups.io/g/cosmacelf/topics
Assembly Programming on the 1802:
https://tomswan.com/pub/collections/
Data sheets for the CDP1870, etc.:
http://www.cosmacelf.com/publications/data-sheets/
#comx35 #comix35