VT100 Character ROM image - test-drb@ccmp.vtda.org

4 Dec 2007

-------Original Message:
Date: Tue, 4 Dec 2007 07:03:32 -0800
From: dwight elvey <dkelvey at hotmail.com>
Subject: RE: VT100 Character ROM image

...
 > From: derschjo at msu.edu> > >> >
> I tried to dump the ROM over the weekend and had no luck whatsoever, > regardless
of what I tried to read it as. I suppose it wouldn't be out > of the question to
recreate the contents manually based on the patterns > from the tech manual;
there's not a ton of data in there, it's just > tedious :).>  Hi
 I've rarely seen ROMs that have 100% match between pin of
a 2716. Most have at least one enable pin that is inverted.
Also, to prevent damage, I recommend disconnection the program
voltage wire with a socket adapter. This wire would be either
tied high or low at the ROM depending on selects chosen for
that ROM.
 On a 2Kx8 ROM, there are usually 3 enables that need to have
the correct levels on. When I've read ROMs in the past, I've
usually put SPDT switches on these wires. One can then play
with the combinations to get the correct one that reads the
data in the ROM.
Dwight

---------Reply:
Dwight's quite correct; many ROMs included partial address decoding.

Aren't there schematics in any of the bitsavers files (or elsewhere)?
Enable pinouts & levels should be obvious if you have a schematic;
a lot less work than creating a ROM from the dot patterns...

m