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From: droms@burdvax.UUCP
Newsgroups: net.wanted,net.micro.cpm
Subject: Motorola monitor and Xerox 820-I board
Message-ID: <1578@burdvax.UUCP>
Date: Tue, 12-Jun-84 08:23:58 EDT
Article-I.D.: burdvax.1578
Posted: Tue Jun 12 08:23:58 1984
Date-Received: Thu, 21-Jun-84 01:17:29 EDT
Organization: System Development Corporation, Paoli PA
Lines: 18

I bought a Motorola TTL-compatible monitor from the Xerox Mfg.
Outlet in Texas which was claimed to be compatible with the
Xerox 820-I boards from the same source.  Has anyone else
tried using this combination of equipment?  I'm having a problem
with the video display beginning before the vertical retrace is
complete; about 10 horizontal scans are "folded" down from the
top of the screen and overlap the remaining horizontal scans.
I know the board works correctly when connected to a composite
video monitor through an appropriate composite video generator.
It appears that the vertical retrace is slower than the video
generator on the 820-I board expects.  Should I blame the monitor,
the 820-I board or an incompatibility between the two?  If the
two are incompatible, what can I do to fix them?  One solution
is to stretch out the vertical retrace time on the 820-I board;
unfortunately, that timing is all done with counters and requires
cutting traces to adjust the values loaded into the counters.

					- Ralph Droms