The PROWLER DIY section
||| Scoping out Jaguar RGB
||| By: Duncan Brown
/ | \ GEnie: D.BROWN38 Internet: BROWN_DU@Eisner.DECUS.Org
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There are a lot of connector pinouts floating around for the A/V
connector on the back of the Jaguar. None of them enabled me to
successfully construct an RGB cable, so there was only one answer:
SCOPE IT! Here, then, is what an hour with my trusty oscilloscope has
taught me. I now have my development Jag feeding a 19" RGB monitor
salvaged from an old video game (Stargate, in this case.) To anyone
still doubting that the Jag provides arcade-quality graphics in a $250
console, you need only see it on an arcade monitor to be convinced!
The biggest point of confusion on the various connector pinouts seems
to be the numbering scheme. I will try to clear that up. Here is how
the connector appears in several Atari documents (like the one
provided in GIF format by AEO):
TOP (duh)
1A 2A 3A 4A 5A 6A 7A 8A 9A 10A 11A 12A
1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B 12B
The important point is that this is looking at the PCB edge connector
from the BACK side of the Jag. (Or, if you prefer, looking at the
cable connector from the side the *wires* connect.) Pin 1 is on the
side towards the DSP connector.
And here are their functions:
1A Left audio
2A Audio GND
3A GND
4A GND (chroma)
5A RGB Blue
6A Horizontal sync
7A RGB Green
8A Chroma
9A GND (?)
10A +5V (?) No warranty expressed or implied on these....
11A +5V (?)
12A
1B Right audio
2B Audio GND
3B GND
4B RGB Red
5B Composite (Vertical) Sync
6B
7B GND (Luminance)
8B Luminance
9B GND
10B GND (composite vid.)
11B Composite video
12B
Some specs on those signals:
RGB pins: range from about .9V (black) to 1.2V (full drive)
Hsync: baseline is about 3V, with 20uS pulses to ground about
every 62uS
Comp Sync: baseline is about 5V, with 20uS pulses to .2V for hsync,
and 250uS pulses to .2V for vsync (about every 16.6mS).
Each vsync pulse is surrounded on either side by about
200uS of double-frequency (about every 31uS) hsync-type
pulses.
Which all means that to hook your Jag to an RGB monitor, it must
accept *analog* RGB signals, be able to sync to a horizontal frequency
of about 16KHz, and a vertical frequency of about 60Hz.
In the case of an old arcade game monitor, the specs are dead-on, but
there is one thing to note: you must hook the sync signals to the
"negative sync" inputs of your monitor. In the case of my Stargate
monitor (an Electrohome) that meant using the sync signal connections
on the little 3-pin connector, which is normaly unused by Stargate. If
you have a monitor that only accepts composite sync, then the 5B
output should work fine. If you need separate syncs, use 5B for the
vertical sync.
//// Some background on me:
I have "spent" (some would say "wasted"...) a lot of time and energy
throughout my life fooling around with video games. My love for
pinball and video games actually led me to own my own arcade for 3.5
years, starting in 1982. During that time and beyond, I
reverse-engineered several arcade games, generally for some specific
purpose. I created heavily modified versions of Asteroids for a
Psychology researcher at the University of Denver; I created new tube
shapes for the Tempest in my arcade; I wrote a complete new game from
scratch to run on Williams hardware (Stargate, Robotron, that era);
and so on. More recently I have been helping a researcher at the
University of Virginia who is using an Atari Race Drivin' Panorama
(3-screen version) as a driving simulator.
Other than tiny amounts of pay for the research work, all of this
stuff has mainly been for my own amusement; there was never any real
purpose to it all. But now it has finally become clear: it was all to
prepare me for my true destiny: JAGUAR DEVELOPER! I am offically
enrolled as a 3rd-party Jaguar developer, and am very impressed with
the platform. In fact, until now I had never even purchased a home
video game console system. With a few real arcade games scattered
around the house, why would I want to buy some cheesy toy system? But
the Jaguar has changed all that. It truly is an arcade-class machine
in a $250 box!
I have a (fairly) understanding wife, and two boys aged 2 and 6 who
obviously enjoy my odd love of video games! I drive a 1960 Land Rover
88 as my daily transportation, and enjoy going off-road with it with
the area Land Rover club. The Rover is 2 years older than I am....
I have a day job as Manager of World-Wide Systems Operations (whew!)
at a contract research firm located in Charlottesville, VA. The
Jaguar development is strictly nights and weekends... but I don't
sleep much, so that helps.
So, that's me in a nutshell. I hope these RGB pinout specs will be of
some help to someone, as I know I wasted a lot of time trying to do
this based on incomplete information, but now that it's working, the
results are worth it!
PROWLER The Atari Console Disk Magazine February 27, 1996
Copyright (c) 1996 All Rights Reserved Issue No. 01