🚀 go-pugleaf

> I currently own a (lowly) TRS80 CoCo running OS9.
I assume this apology is for net.amiga only! ;-)

> Like all sensible people, I really want n Amiga,
> but like many sensible people, can't afford one.
What's wrong with Atari ST?  Not that I should talk,
having just bought a Coco III (very sensible, non?)

> One possibility is to buy the new CoCo III that
> has just been released by Radio Shack.  The CoCo III
> uses an analog RGB monitor, just like the Amiga.
> Well, not quite, the CoCo has separate RGB and sync
> signals, whereas (if my info is correct) the Amiga
> tacks sync onto the G (green) line.  Is this true?
> Is there anyway to adapt the two?  This would allow
> me to buy a CoCo now, and later expand to the Amiga
> while not losing the greater part of my investment.

Good idea.  I can't speak for most monitors, but my
lowly (really -- lo-res TV dot-pitch) Zenith 131 that
I paid $150 for has both composite and analog (whew!) 
RGB inputs.  These have two pins each for either polarity
of separate H and V synch.  However, the manual says you
"must apply composite sync to both H and V."
I suspect you could just feed the Amiga Green signal
to both +sync pins.

I 'scoped my Coco III RGB outputs and found that both syncs
are positive TTL (full 5 V) pulses, whereas the video RGB
leads are much less.  The Amiga could certainly superimpose
5-volt pulses on top of the Green; the right monitor would ignore
the low-level video but trigger on the pulses.

Find out what the Amiga G & Sync looks like.  If it's as above,
then both computers should be able to share a monitor whose
sync thresholds are high enough.

Be sure to get a monitor with separate sync inputs and strap
the G to both of them.  That is, Radio Shack's monitor may
work with the Amiga, but not the reverse!

A friend is looking into your same question wrt the ST,
and I'm making up a cable to run the COco III into my Zenith.
Will keep you "posted" -- mike k
-- 
Mike J Knudsen    ...ihnp4!ihwpt!knudsen
Bell Labs (AT&T)   (312)-979-4132 (work)
Nobody pays for my opinions, which are mine alone.
"A mind is a terrible thing to waste, but the pay is good."

In a previous article, someone asks about RGB signals on the Amiga...
I've lost track of who (sorry).  I originally replied via mail, but
to prevent this from generating too much traffic and (mis-) information...
(at least, misinformation I didn't start :-)

(original question:)
>> Well, not quite, the CoCo has separate RGB and sync
>> signals, whereas (if my info is correct) the Amiga
>> tacks sync onto the G (green) line.  Is this true?
>> Is there anyway to adapt the two?  This would allow
>> me to buy a CoCo now, and later expand to the Amiga
>> while not losing the greater part of my investment.
 

     THE AMIGA DOES HAVE SEPARATE SYNC OUTPUT AVAILABLE.
     --------------------------------------------------

I am using a DEC VR241 color monitor (an industrial monitor which gives
a really beautiful picture).  SYNC is driven from the composite sync
output on the Amiga.  The Amiga also has separate horizontal and vertical sync
outputs, although I haven't used these.

I don't *think* SYNC is also superimposed on the GREEN line, although I've 
never actually checked this.  If it is, then my monitor certainly fails to
pick it up.  Of course, since I got it free from someone who thought it was
broken, anything is possible :-)

> Keywords: Monitor
> Xref: cbmvax net.micro.6809:248 net.micro.amiga:3453

> The CoCo III uses an analog RGB monitor, just like the Amiga.
> Well, not quite, the CoCo has separate RGB and sync
> signals, whereas (if my info is correct) the Amiga
> tacks sync onto the G (green) line.  Is this true?
> Is there anyway to adapt the two?  This would allow
> me to buy a CoCo now, and later expand to the Amiga
> while not losing the greater part of my investment.
> 
> Comments are appreciated.
> 
> ....!ihnp4!alberta!calgary!ingoldsby
> 
>      Terry Ingoldsby

The Amiga has available at its video connector Horizontal, Vertical, and
composite sync signals; they're not mixed in with G.  The Amiga will work
with virtually any NTSC standard analog RGB monitor.  If the CoCo III
does as well, then you'd be in business for a potential upgrade later
on.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dave Haynie	{caip,ihnp4,allegra,seismo}!cbmvax!daveh

	"Laws to supress tend to strengthen what they would prohibit.
	 This is the fine point on which all the legal professions of
	 history have based their job security."
						-Bene Gesserit Coda

These opinions are my own, though for a small fee they may be yours too.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

> > has just been released by Radio Shack.  The CoCo III
> > uses an analog RGB monitor, just like the Amiga.
> > Well, not quite, the CoCo has separate RGB and sync
> > signals, whereas (if my info is correct) the Amiga
> > tacks sync onto the G (green) line.  Is this true?
> 
I don't believe that the amiga camps the sync on the Green line, and hauled out
the schematic package to check.  With all of the options the designers gave us
for outputs, it should be possible to hook up nearly any monitor, though many 
will obviously not be "up to amiga standards" of dot pitch, etc.

Looking at the schematic of the Amiga, the following signals are available
on the rear-panel d-connector that normally has the amiga monitor connected:

R, G, and B on pins 3, 4, and 5 (respectively)  These are the standard
	amiga outputs (analog rgb)

DR, DG, DB, and DI on pins 9, 8, 7, and 6 (respectively)  These appear to
	be "digital rgb and Intensity" outputs ala the ibm pc, but I haven't
	tried them as such yet.

QCSY* on pin 10, A composite sync.

HSY* on pin 11, a horizontal sync.

VSY* on pin 12, a vertical sync.

In addition, there is a composite video output on the backpanel (rca phono
	style jack) and the rf modulator output jack with another buffered
	output of the same composite signal plus left and right audio 
	channels.

Hope this helps out a bit.....

8-)                  8-)               8-)           8-)              8-)
By the way, there was a "discussion" about hooking up a monochrome monitor
	for those of the "amiga:vs:mac" wars.  I simply plugged a composite
	monitor into the rca jack composite out of the amiga, and there I
	was, "instant mac", same little 9 inch screen, monochrome image.
	no roll, horizontal tear, jitter or other hassles, just plug-n-play.
	Don't like the tall letters of the amiga on a 16" screen?????
	just plug in a 9" monochrome and see how the "resolution of the mac
	compares"			(-8        (-8       (-8        (-8


	


The schematic I am using for these signals is part of the schematics and
expansion specifications available from Commodore (don't have the address
any more, sorry)  
-- 
--Rick Frazier--  DISCLAIMER: The above is individual opinion (the result of my
imperfect recall of facts, real or imagined) in no way representing anyone else.
UUCP:  {decvax,ucbvax,ihnp4}!decwrl!mips!rick         DDD: 408-720-1700 x278