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Re: [N8VEM-S100:785] Re: Help with S-100 VDP board VGA output
Couldn't you just use a LM1881 synch separator on the CSYNC signal. CSYNC
should basically be just the signal without any video related data.
> Hi, it is possible that if CSYNC* = HSYNC* AND VSYNC* then VSYNC* =
> CSYNC* XNOR HSYNC*
> Leon, would you please confirm that CSYNC* and HSYNC* pins on the
> V9938 are TTL level outputs?
> If they are TTL outputs and you happen to have 74LS86 XOR and 74LS04
> inverter chips available would you please test to see if we can
> reconstitute VSYNC* signal?
> Thanks and have a nice day!
> Andrew Lynch
> On Apr 1, 8:41 pm, "Andrew Lynch" <LYN...@YAHOO.COM> wrote:
>> I've been working to update the S-100 VDP with the AY-3-8910 sound
>> and convert to VGA output.
>> However, I've hit a major roadblock and need some help to move forward
>> this project.
>> It turns out the V9938 does not generate a separate VSYNC signal. It
>> generates HSYNC and a CSYNC signals separately however both CGA and VGA
>> require separate VSYNC and HSYNC signals.
>> I imagine there is some relationship between CSYNC and HSYNC where you
>> synthesize VSYNC but after much studying the V9938 datasheet and
>> Google searches I don't know how to do it.
>> Please take a look at the V9938 datasheet and let me know if generating
>> VSYNC is possible and how to do it. Without a separate VSYNC we lose
>> hope of even partial VGA compatibility!
>> Thanks and have a nice day!
>> Andrew Lynch
>> Printing S100_VDP-sch.pdf