19 Sep
2002
19 Sep
'02
5:46 a.m.
Loboyko Steve wrote:
ADM-3A
I read the upper and lower case chips, programmed a lower case
2716, and made a small adapter from to make the 2716 "look" like
a 2513 in the socket, installed the chips/adapter, flipped a few
switches, and voila!
Nice work Steve, and thanks for the PROM files.
A very trivial question: can you see any particular reason why the
glyphs in the lowercase ROM run backwards (apart from "address lines 3 -
8 are inverted"!) Does this make anything simpler? I've just found the
ADM-3 Maintenance Manual, and it appears to have the same configuration,
but it just says
"... the lower case ROM is a custom masked part. The one unusual thing
about this is that all of the address lines into the lower case
character generator are inverted."
No explanation! And it can't be all of the lines on the ADM-3a, because
the 8 scan lines run top to bottom, as with the upppercase ROM.
- Paul