Re: Protecting XY monitors...

From: Clay Cowgill <clay_at_supra.com>
Date: Fri Sep 05 1997 - 18:31:26 EDT

My idea from a while back was to use a micro (PIC! :-) and four comparators
to monitor the deflection. I hadn't really decided at what point to take
the signals though...

Anyway, the idea was to be sort-of a digital based spot killer that relied
on seeing activity in all four quadrants of the screen. If there wasn't
activity in every quadrant every couple milliseconds (or some number
probably determined by experimentation), then activate the spot killer.

What I wanted to be able to do was use other vector games (like the Sega
stuff) with a WG without having the spot killer "attack". This also allows
me to make some new vector hardware without having to draw vectors at
"full" speed at first and still be able to see the picture on a "real"
monitor. (I like running stuff slow at first so I can get good data with a
scope or analyzer, and once it's working crank the speed up for
performance.)

Carrying it a little farther it wouldn't be hard to teach the PIC to:

1) if no activity in all four quadrants in XXXms, then blank the Z

2) if *still* no activity in all four quadrants in YYYYms, then cut power
to the monitor

The idea being for #1 that the software is starting or resetting or
something and just needs some time to get going. The idea behind #2 is
that the game board has failed and might be holding the deflection at +Xmax
and +Ymax (or something) and rapidly cooking your output transistors...

-Clay

Clayton N. Cowgill Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc. clay@supra.com
\/ Communications Division http://www.supra.com/
Received on Fri Sep 5 14:31:08 1997

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