Re: [stella] does the processor stop during VSYNC?

Subject: Re: [stella] does the processor stop during VSYNC?
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 06 Apr 1998 17:28:27 +0200
At 22:21 05.04.98 -0500, you wrote:

>When you do a VSYNC, does the processor wait until it's really time for
>the next frame to begin before processing resumes (like a WSYNC), or
>does it just send the sync signal to the TV and keep on running
>regardless of how many scan lines have passed since the last time?  I'm
>hoping it's the former, of course, but I'm guessing it's probably
>really the latter.  The emulator I'm using (Stella 0.7) seems to think
>any number of scan lines in a frame is fine, but I don't know how much
>faith I should put in its emulation.

Unlike the Wsync register, Vsync is not a strobe register. Instead
it lets you turn the vertical sync signal on and off. So what you 
have to do to get a stable picture is: make sure the correct number
of scanlines have passed, turn on Vsync, wait for 3 scanlines via 
Wsync and turn off Vsync.

Ciao, Eckhard Stolberg

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