Subject: [stella] FWD: help with Indirect Indexed Addressing From: KirkIsrael@xxxxxxxxxxxxx Date: 8 Sep 2003 03:22:30 -0000 |
Sorry if this is a repost...it didn't seem to go through? Aargh, this is maddening. On my way to something like skipdraw, I realized that I was going through too much logic to figure if I should draw the wingup or the wingdown graphic, I needed to set a 2 byte pointer to current graphics frame in the VBLANK. I just started with P0: I set up a 2 byte variable: pointerP0Graphic ds 2 In my initialization I set up the second byte of that with the page I'm putting all the graphics on: LDA #>GraphicsPage ;grab the hight byte of the graphic location STA pointerP0Graphic+1 later, I either do LDA #<WingUpGraphic+1 ;add in the low byte of the graphic location STA pointerP0Graphic or LDA #<WingDownGraphic+1 ;add in the low byte of the graphic location STA pointerP0Graphic Now, I'm pretty sure that that's all correct, because I can put that graphic inplace of the score, on its just about what I expect: LDA (pointerP0Graphic),Y ; LDA (pointerP0Score),Y STA GRP0 It flaps and looks ok, just a little truncated, which makes sense. Now, for now I'm using a byte, p0DrawBuffer to buffer, and then putting that in GRP0 at the begining of the line. So my logic has P0VisibleLine counting down from 8 to 0, showing which line is visible. LDA #00 ;if the p0VisibleLine is non zero, ;we're drawing it LDX p0VisibleLine BEQ FinishPlayer0 ;we're done drawing DEC p0VisibleLine LDA (pointerP0Graphic),X ;what's wrong with this??? ;LDA #%10011001 FinishPlayer0 STA p0DrawBuffer Now, because I can put the pointerP0Graphic into score, I think I'm setting it right. And that commented out LDA #%10011001 when restored, shows that the Accumlator->P0DrawBuffer ->GRP0 is working fine, because if I uncomment it I see that pattern. Commented, GRP0 seems to be random garbage that varies even with P1 flapping, so I don't know where the heck LDA (pointerP0Graphic),X is getting its data from... Is there some gotcha to use Indirect Indexing with the X register I'm missing? It's driving me nuts, because it seems to be isolated to that line... Full source and binary at the top of http://alienbill.com/joustpong/ Doggone it. I thought I was doing well to. -- KirkIsrael@xxxxxxxxxxxxx http://kisrael.com "The desires of the heart are as crooked as corkscrews." --W.H.Auden ---------------------------------------------------------------------------------------------- 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] 6 Digit Code Frustrati, Happy_Dude | Thread | Re: [stella] FWD: help with Indirec, Andrew Davie |
[stella] 6 Digit Code Frustrations, Chris Larkin | Date | Re: [stella] FWD: help with Indirec, Andrew Davie |
Month |