Wanted: ASM-48 for Intellec MDS-2
fulivi at tiscali.it
Fri Apr 3 03:30:32 CDT 2015
I'm going to use the ASM48 assembler to write a firmware from scratch
for the PIO (parallel I/O) microcontroller on the IOC board. It's a
8041A (ROM masked version) and it's labelled A72 on the schematics.
By looking at the picture you took of an IOC board it's clearly a masked
ROM (no UV window). Because of this I think it would be very hard to
find the ROM image. AFAIK dumping it would require a microphotograph of
the die and a lot of patience to recover the ROM bits....
Anyway, for the MESS emulator having a functional PIO is important
because it controls (among other things) the line printer output (J6).
This is the functionality I'm going to address. All the other parallel
I/Os (paper puch/read and PROM programmer) are going to be "plugged" in
the firmware (i.e. made to appear disconnected).
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