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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: TheGoose on February 12, 2009, 06:50:43 PM

Title: RGB output sync?
Post by: TheGoose on February 12, 2009, 06:50:43 PM

Hey,

Is the Amiga RGB output separate or a combined sync?

What does this mean 'separate or commbined' sync - any technical takers?

 

Title: Re: RGB output sync?
Post by: Damion on February 12, 2009, 07:14:33 PM

Amiga RGB has a separate horizontal and vertical sync output. Combined sync (composite sync, or "sync on green") combines them both on one output. I imagine something like an XOR gate is used to combine the signals, but someone else would have to expand on that. :)

*edit* Found a basic glossary here (http://www.monitorservice.com/faqs1.html) (applies mostly to CRTs). BTW - depending on the required input, RGB + csync also works fine.

Title: Re: RGB output sync?
Post by: Speelgoedmannetje on February 12, 2009, 07:20:02 PM

IIRC the horizontal/vertical sync is only for digital RGB, which outputs max. 16 colours, so that's of no use.
Combined sync it is.

Title: Re: RGB output sync?
Post by: Damion on February 12, 2009, 07:30:23 PM

Quote

Speelgoedmannetje wrote:
IIRC the horizontal/vertical sync is only for digital RGB, which outputs max. 16 colours, so that's of no use.
Combined sync it is.

Either separate or combined will work (no color restriction using separate sync signals).

Title: Re: RGB output sync?
Post by: meega on February 12, 2009, 07:55:36 PM

Quote

TheGoose wrote:
Hey,

Is the Amiga RGB output separate or a combined sync?

What does this mean 'separate or commbined' sync - any technical takers?

 

It's both.  ;-)

The standard RGB sync is combined H/V (X+Y) on one pin, active "high" iirc. That is the only one you need for "normal" screens. There is also a V (Y only) signal on another pin, active "low", again iirc. If you use them both (suitable monitor and selected screenmode required) then they give separate control of the H and V scan rates.

Title: Re: RGB output sync?
Post by: TheGoose on February 13, 2009, 12:10:58 AM

Thanks guys. I think that helps me. Want to ask this too, if the composite out on an A1000 works (all color represented) does that mean the machine's RGB is working ok?

Put another way, could you have a functioning composite out and a broken RGB out?

 :-?

Title: Re: RGB output sync?
Post by: Daedalus on February 13, 2009, 12:34:31 AM

Yeah, you can have your RGB port damaged but composite will still work fine. It means your video generation circuitry is working just fine, and the fault lies somewhere close to the RGB port itself. The signals are there, they're just not getting out of the port properly. Check the motherboard for cracked joints around the RGB connector, damaged traces nearby, and check the actual RGB cable and plugs to make sure they're ok.

Title: Re: RGB output sync?
Post by: Skippy on February 13, 2009, 01:55:07 AM

Daedalus is absolutely correct.

I've had numerous a1200s in the past with either fried RGB ports, damaged RF, etc and the alternate port has been fine.

In fact my current a1200 build I use via the RGB port and the composite, but the RF is faulty.

Skippy.

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Title: Re: RGB output sync?
Post by: TheGoose on February 13, 2009, 05:06:41 PM

Damn! Maybe this is why my neobitz never really worked. And, maybe my 1950 monitor really isn't broken! And maybe the A1000 was to blame this whole damn time!

Great Scotts!



  :lol: