Subject: DECmate II Video Connections

From: [email-masked] (Charles Lasner)
Date: Sat, 20 Mar 1993 15:28:11 GMT

I am reposting an article from comp.sys.dec.micro that applies to this group
along with some comments.  Perhaps someone has some clues as to what's going
on here.

Newsgroups: comp.sys.dec.micro
Subject: Re: Pinout of DECmate II videoconnector ?
From: [email-masked] (Don Stokes)
Date: 20 Mar 93 07:16:29 GMT

The 15pin monitor cable connector pinouts are:

	1	Blue return
	2	Green return
	3	Red return
	4	Mono return
	5,6	Ground
	7,8	+12VDC
	9	Blue video
	10	Green video
	11	Red video
	12	Mono video
	13	Monitor present
	14	Keyboard receive
	15	Keyboard transmit

Signals are straight video.  VR201 monitor gets its power through the +12VDC
line (pins 7&8), VR241 has its own power supply.  I'm not sure where the
sync comes from in the colour signals (green?), but it's there in the mono
signal.

This pinout is pretty much the same for all DEC monitor cables.

--
[End of copied material; unrelated parts deleted for bandwidth considerations
only, etc.]

My experience with the DM II (as opposed to the III and III+) is that the
VR-241 doesn't work as the primary monitor.  Note that the recommended
configuration for a II is a mandatory VR-201, and if the graphics board is
present (I have one for the II, not the III/III+) then you can optionally add
the VR-241 to the 15-pin connector on the graphics option.  (Monochrome
graphics come out of the main connector because there is an after-thought
jumper between the graphics board and the motherboard to route the text to the
graphics card and also graphics to the main video out on the motherboard.

This is part of the major hardware ECO to the older vintage DECmate II
motherboards which were simultaneously not compatible with the hard disk board
set and also not compatible with the graphics board.  Beyond a certain level, 
this was merely due to the ROM contents, but this affects only the hard disk
aspect.  (I have disassembled the relevant ROM versions to confirm this, etc.)

The ECO consists of adding on a small two-prong connector to an available
small patch of empty board region, and then performing quite a few adds and
deletes (about 25 wires) so that the option board functions correctly.  (The
System Test Diskette won't even acknowledge the existence of the graphics
option without the ECO, etc.)

The DM II graphics color cable is visually similar to the Rainbow cable,
which I believe is the same cable for a DM III/III+ configured with the
graphics board within.  In essence, you have a one-monitor system with the
ability to have either a VR-201 or VR-241, but not both, while a Rainbow
can have either one or the other or both, the last case being similar to
what's thrust upon you in the DM II case, and the former cases being the
same as the III/III+.  That Rainbow cable was given to my by a Rainbow person
along with a VR-241.  This is the kind with the three striped R G B BNC cables
at one end, and the 15-pin connector at the other end.  The wires come out of
a large molded block with a strip of velcro on the back to hang on the back
of the monitor.  Additionally, the keyboard plugs into the block.

I have also used this cable on a VT-240.  It worked fine, and allowed me
to plug the keyboard into either the VT-240 or the provided socket on the
cable.  My only disappointment was that the terminal identifies as a VT-240
not a VT-241, even though it also says VT-240 when you use a VR-201 with the
keyboard in either place.  I thought it could identify which monitor you are
using and behave accordingly.  It is conceivable it is working, yet just not
proclaiming it at the ID, etc.  Any ideas as to how to force the issue that
the VT-241 indeed is recognized as such?  (Does it return a terminal escape
sequence that is different if a VR-241 is installed?)

Although similar, the DM II cable is clearly different.  It lacks entirely the
modular socket in the block (and has no provision for the velchro stick-on).
When that cable is used on the VT-240, you are of course forced to connect the
keyboard to the internal connector on the back of the VT-240, but in any
case, it comes up with an error message (I forget the exact verbiage) and then
proceeds to otherwise function correctly.

The Rainbow cable doesn't work in either 15-pin DM II positions.  I.E., it
won't allow the DM II to come up with color primary monitor, and the cable
doesn't allow the use of the VR-241 on the graphics board either.

Just before the recent blizzard in North America, I received (it's somewhat
"buried" at the moment, so this may have to wait for awhile) a bizarre cable.
This may be an in-house DEC special cable, but essentially, it's a cable that
on one end looks like the Rainbow cable, complete with block and three R G B
BNC leads, but the other end has *two* 15-pin connectors!  (And of course, it
should be interesting figuring which 15-pin goes to which connector!)

Anyone have any clues on the above?

cjl

---

From: [email-masked] (Don Stokes)
Date: 20 Mar 93 23:59:10 GMT

[email-masked] (Charles Lasner) writes:

That onfo came from Field Circus.  I wanted to (and did) hook up a VR201
to a GIGI.  

The pinout is standard from DECmates to workstations; however note that 
mono only systems don't use the colour lines and vice-versa.  There's 
only one "monitor present" line (tied to ground in the monitor, or in the 
connector block for those monitors that use BNC connectors), so a machine 
can't tell if there's a VR201 or a VR241 at the other end.  (Actually, if 
the thing at the other end draws power, it's a 201, since the 241 has its 
own power supply, but I don't believe that's implemented anywhere.)

Thus, you can (in theory at least, ie assuming the cable brings does the
right thing with all the lines) use a VR201 with the same cable on a
VT240, DECmate or Rainbow; likewise with the VR241.  The cable is not so
much a "DECmate" (or whatever) cable as a "VR201" (or VR241) cable. 
The VR201 cable is the same pinout at both ends -- you can bang two of
them together if you need a longer cable to the monitor/keyboard.  (I
think it brings the colour lines out as well (which the VR201 ignores),
but I'm not sure.) 

>From your commemts below, it sounds like while the VR201 cable is pretty 
much standard across the board, the 241 cables have some bogosities in 
their implementations.

>VR-241 doesn't work on it at all.  Note that the recommended configuration

That will be because the VR241 doesn't listen to the mono line, and the 
mono socket of the DECmate doesn't put anything on the colour lines.  Try 
re-wiring the mono line from DECmate to the green (I think -- whichever 
one generates the sync) line of the monitor.

>I have used this cable on an actual VT-240.  It worked fine, and allowed me

Nothing changes on a VT240 whether there's a mono or colour screen on it;
it doesn't detect the 241.  Tha name "VT241" is ordering information
only; what you got when you ordered a VT241 was a box with "VT240" on the
front and a VR241 on top of it.  The 240 base unit generates both colour
and mono output, regardless of what's on the other end of the cable, and 
the ID sequence is identical.

>Anyway, the DM II cable is different!  It lacks entirely the modular socket
>in the block (and they didn't provide for the velchro stick-on).  When
>that cable is used on the VT-240, you are of course forced to connect the
>case, it comes up with an error message (forget verbiage) and then proceeds
>to otherwise work anyway.

Maybe they were lazy with that cable -- left out the "monitor present" 
jumper & didn't bring out the keyboard lines, probably.

>won't allow the DM II to come up in color primary monitor, and the cable
>doesn't allow the use of the VR-241 on the graphics board either!  Any clues
>as to what's different here?

The 241 won't work at all in the mono socket.  Don't know why it won't 
behave in the gpx socket -- time to break out a meter and look!

>Just before the recent blizzard, I received (it's somewhat "buried" at the
>moment, so this may have to wait for awhile) a bizarre cable.  This may be
>an in-house DEC special cable, but essentially, it's a cable that on one end
>looks like the Rainbow cable, complete with block and three R G B BNC leads,
>but the other end has *two* 15-pin connectors!  (And of course, it should be
>interesting figuring which 15-pin goes to which connector!)

Dunno.  Again, out with the meter!

--
Don Stokes, ZL2TNM (DS555)                        [email-masked] (home)
Network Manager, Computing Services Centre            [email-masked] (work)
Victoria University of Wellington, New Zealand              +64-4-495-5052

---

From: [email-masked] (Bob Leigh)
Date: Thu, 25 Mar 1993 15:45:59 GMT

>From the information you've given, I think you may have a Rainbow dual-monitor
cable.  Earlier in your article, you stated:
>In essence, you have a one-monitor system with the
>can have either one or the other or both...

If that's what it is, then you should have one male connector (for the
monochrome monitor) andand one female connector (for the Rainbow system box).

I've got a document called "DUAL MONITORS ON A RAINBOW" that explains how
to construct such a cable.  I don't have the author's permission to post it
here, but send me e-mail if you want a copy.

-- 
Bob Leigh	 [email-masked]		 (617) 641-2421