CSYNC with VGA driver

Ken Peterson

I'm using the VGA driver to provide an analog RGB signal with composite sync.· I have seen in other threads that you can combine HSYNC AND VSYNC using an XOR gate or resistor and diode (wired-OR).·

I found that by changing two lines in the VGA driver, I can have VSYNC and HSYNC going out on the VSYNC pin, effectively doing the XOR in software.

My question is this:· I want to re-claim the HSYNC pin to use it for something else.· If I set the PINS field in VCFG to 11111101, I can do this, right?

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The more I know, the more I know I don't know.· Is this what they call Wisdom?

deSilva

It most likely will.. which means, I have not yet tried it, but it is consistent with my understanding of how the Video Logic works

Another possibility would be to OVERRIDE the hsync, forcing the corresponding bit in the 8 bit video-out to zero and setting it when needed by a different OUTA instruction or counter. However this would not allow it to be configured as an input pin...

Ken Peterson

I suppose I can do some experimentation to determine if I can use that pin or not.

I just changed the VGA object so that instead of toggling the HSYNC pin when doing the horizontal sync, it toggles the VSYNC pin instead. Checked the SYNC on the scope and it gives me just what I wanted. It works because it uses XOR to do the toggling.

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The more I know, the more I know I don't know.· Is this what they call Wisdom?