Subject: [stella] What I've got so far From: Pete Holland <petehollandjr@xxxxxxxxx> Date: Wed, 7 Jul 1999 17:15:49 -0700 (PDT) |
Okay, gang. Here's what I've got. First up, supposing I use a BEQ, writing it as: BEQ #0 (I believe #0 means numeric value zero, right?) Does the computer check the last value to be changed against the value or location I list after the BEQ command, like if I Decrement X (DCX?), or does it compare the X, Y, and A registers all against the value after the BEQ? I don't have the commands handy, but I recall commands that allowed me to INCrement or DECrement things held in actual memory locations. With this in mind, how close is this to what I need to do for the solitaire game? WSYNC VBLANK During this VBLANK, I put a couple of commands--nothing heavy. I then VBLANK again, start the next command, etc. I do this thirty-seven times, breaking up the commands to fit within the VBLANK times. Next, I start drawing the screen. Assuming I can DEC a value in memory location and compare that instead of constantly shifting the values into and out of the X or Y registers, I do this: LDX #192 STX LINECNT Draw screen commands here. DEC LINECNT BEQ #0 JMP Two commands down Clear all carry flags (just to make sure) JMP Back to the draw screen commands. Clear all carry flags LDX #30 STX LINECNT VBLANK Do any extra game calculations I can here. DEC LINECNT BEQ #0 JMP Two commands down Clear all carry flags JMP back to VBLANK command JMP back to top of all this, start the cycle over Am I getting closer, or no? Also, some other questions. Erik Mooney wrote that during the first set of VBLANK commands, I have time for 800-1000 commands. A FAQ I boosted off the 'Net says I have time for 80-100. Did someone misplace a zero, or are both answers correct and I'll discover how to do both with practice? What color is produced by VBLANK? If I need extra time to complete game calculations, like in the Columns example about a month ago, can I start VBLANKing as soon as I draw the last part of the screen needed, buying myself a little more time to work on things? To save time, I'm envisioning in the mental flowchart I came up with then starting the VBLANK after VSYNC with checking for a joystick input. If none, it just bounces through to the screen drawing part. If there is, if first checks what kind it is. If I put the "check what it is" subroutines here, I should be able to just have the computer do a subroutine when needed, and that won't tie up the processor during the VBLANK because, if done right, only a couple of commands will be needed and I can send the program right back to the VBLANK cycle before the beam reaches the edge, right? Am I getting closer, or am I getting all this royally wrong? "We don't need no new set of standards, "We don't need no new set of rules." Operation Ivy -"Take Warning" (With apologies, I know I took that completely out of context.) _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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Re: [stella] Networkable Atari., Kevin Horton | Thread | Re: [stella] What I've got so far, Erik Mooney |
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