Re: [stella] PCAE has 263 Scanlines?

Subject: Re: [stella] PCAE has 263 Scanlines?
From: Erik Mooney <erik@xxxxxxxxxx>
Date: Mon, 19 Aug 2002 11:45:40 -0400
On Sun, 18 Aug 2002 14:32:45 -0300, you wrote:

>PCAE is puzzling me (and ruining my cycle/scanline counting as well)..
>In its debugger there's a "Scan" (CY, CRT beam Y position) variable that 
>is supposed to help the programmer to know in which scanline TIA (and the 
>TV) is. Its value ranges from -40 to 222, which sums up to 263 scanlines. 
>But, according to SPG, 3 Vsync + 37 Vblank = 40 (hence the -40 range in 
>Scan). 192 visible scanlines + 30 Overscan = 222. And, finaly, 40+222=262. 
>It seems that PCAE has an extra scanline!

The scanline count is determined by the software (your program), not the
hardware or the emulator.  If PCAE is showing 263 scanlines total, your
program is probably doing 263, and you've got a bug somewhere. :)

Also, carefully consider zero and all the off-by-one possibilities.  Does
PCAE have a scanline 0?  I'm not totally sure.

Archives (includes files) at
Unsub & more at

Current Thread