DEC VT100 character generator

[Jonathan Gevaryahu]

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Message: 20
Date: Mon, 23 Nov 2009 22:50:31 +0000
From: Pete Turnbull <pete at dunnington.plus.com>
Subject: DEC VT100 character generator
To: ClassicCmp <cctalk at classiccmp.org>
Message-ID: <4B0B11B7.4020304 at dunnington.plus.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Several months ago, someone was looking for an image of the 23-018E2
character generator ROM for a VT100.  A generous reader has given me an
image, which I've uploaded to my website at
http://www.dunnington.u-net.com/public/DECROMs/

Better late than never, I hope!

-- 
Pete						Peter Turnbull
						Network Manager
						University of York


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Pete,
That matches the rom I typed from the vt100 tech manual datasheet for 
MESS. Are you sure someone dumped it from a real chip and didn't just 
submit the rom I typed up (which is now floating around the 'net)? The 
rom is marked as a 'bad dump' in MESS, because I was almost sure the 
typed one is very slightly wrong due to the fact that the sum16 of the 
one I typed does not end with "00", which seems to have been standard 
DEC practice for roms at the time. Hence I was hoping someone with a 
working or scrap vt1xx series board would dump the real thing.

The trouble with most people dumping the original chip seems to be that:
A. it is soldered to the vt1xx board
B. it has uninverted CE (I think...) and a few other pinout oddities 
(see schematic on bitsavers)

P.S. the second optional character rom (only selectable if you have an 
AVO board installed, or a VT102/VT131 which has AVO builtin), labeled 
23-094e2 is also not dumped. This one, fortunately, is socketed on 
systems which have it, and I believe has a normal pinout. I think it 
contains european characters and formatting/word processing characters. 
It might also contain some or all of the technical font used on the 
later vt3xx+ systems as shown here: http://vt100.net/charsets/technical.html

P.P.S. the main cpu roms from a vt1xx with the word processing romset 
installed are also not dumped. I have no idea what the numbering on 
these is though. Two of the CE pins alternate in binary form for the 
chips to allow them to be 'self decoding' and inserted in the four 
sockets in any order! cute, but makes dumping them a bit harder.

-- 
Jonathan Gevaryahu
jgevaryahu(@t)hotmail(d0t)com
jzg22(@t)drexel(d0t)edu