Subject: Re: [stella] That .byte thing From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx> Date: Fri, 25 Sep 1998 15:39:46 +0200 |
At 19:39 24.09.98 -0500, you wrote: >I want to draw an X on the background using the Player0 graphic. >I have some problems. I do not know how to do that .byte thing and when I >do it the hard way (see below) I require 2 STA WSYNCs in order to see >something draw on the screen. Will the .byte command help me out? The RESP0 register is used to position player0 horizontaly. The position depends on when in the scanline RESP0 is hit. The position will remain the same untill it is changed again. Therefore it is not nessessary to hit RESP0 in every scanline. In a scanline, where RESP0 is hit, the player0 graphics will not be displayed. That's why you need two scanlines to see something in your program. The .byte pseudoopcode will insert a byte value at the current address in the ROM. In DASM it can take values in decimal, binary, hexadecimal and octal. For graphics the binary representation would be the best. A routine to read those values and put them into the GRP0 register could look like this. LDX #7 L1: STA WSYNC LDA GRAPHICS,X STA GRP0 DEX BPL L1 GRAPHICS: .byte %00000000 .byte %11000011 .byte %01100110 .byte %00111100 .byte %00011000 .byte %00111100 .byte %01100110 .byte %11000011 In this routine X contains the counter. Since it counts backwards, the graphics data has to be stored upside down. Ciao, Eckhard Stolberg -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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