Subject: Re: [stella] Illegal opcodes...another question From: "Dennis Debro" <ddebro@xxxxxxxxxxxxx> Date: Tue, 14 Jan 2003 00:14:09 -0500 |
Hi Andrew, > It's a real elegant piece of code, Dennis. I agree with you there. I've been using skipDraw (without the illegal opcodes) for Climber for a while now. I'm now trying to understand the illegal opcode way to see if it can save me some cycles. > If the carry flag is set then we branch to the > actual draw code... the y register holds the line number (presumably) > on the screen This is the part I don't understand. When doing skipDraw without the illegal opcodes I see where the y-register is used to keep track of the scanline count. In this piece of code though I don't see where y is updated each scanline. When he skips to the next scanline, the y-register is not updated. The code snippet I posted deals with GRP0. On the next scanline Thomas deals with GRP1 without updating the y-register :confused: Wouldn't the y-register decrement (or increment) per scanline? Take care, Dennis ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
RE: [stella] RE: Illegal opcodes..., Andrew Davie | Thread | [stella] VDELPx, Thomas Jentzsch |
[stella] RE: Illegal opcodes...anot, Dennis Debro | Date | Re: [stella] Collaboration, Glenn Saunders |
Month |