[stella] VBLANK or VSYNC first?

Subject: [stella] VBLANK or VSYNC first?
From: ben <ben@xxxxxxxx>
Date: Tue, 23 Oct 2001 00:54:46 +1000

The stella docs say that there should be 3 lines of VSYNC, followed by
VBLANK for 37 lines.  But it seems combat sets the VBLANK first, then WSYNC
for 3 lines, then VSYNC start, then 3 lines then VSYNC stop.  Which seems
to me like VBLANK is used to 'skip' a frame and get back to the start ready
for an RSYNC?

If not, what is the purpose of writing to VBLANK start?  What actually is
used to allow the programmer to set the real start of the frame (ie
scanline 0, position 0), VBLANK or VSYNC, or both?  It is clear WSYNC is to
wait for the start of the scanline, but can anyone clear up the frame
start/stop easily for me please?

In my emulator, I have managed to RSYNC to the start of the frame, WSYNC to
start of scanline, and sure enough, 3 scanlines later rsync was stopped,
but VBLANK was not following the rules :)


PS: I have read the archives, but could not get an exact answer from an
emulation view, so please excuse me if this has been asked alot :)

Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/

Current Thread