Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!caen!uwm.edu!linac!att!cbfsb!cbnewsc!rls From: rls@cbnewsc.att.com (richard.l.schieve) Newsgroups: sci.electronics Subject: Re: Analog RGB->NTSC ? Summary: Composite sync is available Message-ID: <1991Jun18.125835.14619@cbnewsc.att.com> Date: 18 Jun 91 12:58:35 GMT References: Distribution: na Organization: AT&T Bell Laboratories Lines: 46 In article , mrapple@quack.sac.ca.us (Nick Sayer) writes: > I've managed to obtain at a rediculously low price > a motherboard for the grand old video game "Robotron: 2084". > I know it generates analog R, G, and B signals, and separate TTL > horizontal and verticle sync outputs. Fine and dandy. Setting aside > for the moment concerns about losing definition, is there a way > (I know it won't be easy) to convert this signal into an NTSC > format? Monochrome will do, by the way. > > If not, all is not lost. I know that the Apple IIgs monitor is an > Analog RGB monitor, but it needs a composite sync signal. My bright > idea is to send the TTL H and V sync into the control pins of a pair > of CD4066 "digital switch" elements, whose inputs attach to > a pair of pots, and outputs connect together and go to the > composite sync output. Will this plan work? > > -- > Nick Sayer | Official Scapegoat for the | RIP: Mel Blanc > mrapple@quack.sac.ca.us | MC68HC11 Mailing List. | 1908--1989 > N6QQQ | To subscribe, send mail to | May he never > 209-952-5347 (Telebit) | mc68hc11-request@quack.sac.ca.us | be silenced. Well, this will be the third time I tried to reply to this. If this is the 3rd time you have seen it, my appologies (sp), but as far as I can tell it is not getting out. First of all, I hope you mean board set not board as Robotron is a four board set, ROM, Input, Sound, and Video/CPU. Second, a composite sync is already available, just normally not used. Check out the schematics that show the connector that has the horizontal/vertical syncs and you will find an unused pin. On the schematic for the Video/CPU board you will find that this is a composite sync output. If you do want to make a composite sync out of seperate horizontal and vertical syncs, this is often done by connecting both syncs to inputs of an exclusive-or gate and the output is used as a composite sync. Sometimes some inversions are needed depending on whether you need active low or active high syncs. I hope this helps, Rick Schieve rls@ihlpb.att.com