92198A/MCO00701A EPROM dumps wanted

[brouhaha]

Has anyone dumped the two 2732 EPROMs of the HP 92198A video interface, AKA Mountain Computer MCO00701A? One is the firmware, and the other is the character generator. I no longer have a unit, alas, but I'd like to examine the firmware.

[Paul Berger (Canada)]

I have one here, and will dump the EPROM later when Iget my device programmer out to cut a PLD for a project I am working on.

Paul.

[brouhaha]

Thanks to Paul providing a dump of the firmware, I have partially reverse-engineered the MC00701A/92198A firmware, and put my work in progress on github. I have identified some but not all of the character processing and HP-IL state machines. There are four more HP-IL state machines yet to be identified, and three of them are likely to be R, AH, and SH.

I'd forgotten just how unpleasant the 8048 family is if you need more than 2KB of code.

Interestingly, internally it stores 82 bytes per line, rather than 80. I haven't yet found any reason for this. It sets the CRTC for linear addressing, and uses a table to do a multiply by 82 to get the base address for each display line. Oddly enough, there are 50 entries rather than only 48. Perhaps early in development it was going to have a 25x80 display rather than 24x80.

github does a poor job of displaying files containing horizontal tab characters. Perhaps I'll replace all the tabs with spaces.

The makefile verifies that the binary file generated by the assembler has the same SHA256 hash as the original firmware.

[rprosperi]

Possibly it supports 82 bytes per line to allow for 80 displayed characters + CR + LF ?

[brouhaha]

(05-12-2024 12:20 PM)rprosperi Wrote:  Possibly it supports 82 bytes per line to allow for 80 displayed characters + CR + LF ?

Interesting idea! In normal mode, the CR and LF don't get stored into display memory. Perhaps in monitor mode they do.