Subject: [stella] Any guru to solve a problem with the ROL instruction ? From: Christian Bogey <khryssun@xxxxxxxx> Date: Sat, 17 Apr 2004 20:38:46 +0200 (CEST) |
Hi, I wrote a little demo to try to make some effects using playfield and I've got a bug in my program but I can't find why it occurs :-( Maybe one of the 6502 gurus here may help me ;-) I'm using the ROL instruction to modify the patterns of PF0 and PF2 (I'am using shadows number in ram) and I noticed : * Using the ROL instruction 1 time gives a good result. * Using it 2 times makes a total mess in the Playfield display. * Trying to compile with the first line only, gives a good result (ROL PF0 Value). * Trying to compile with the second line only, gives a good result (ROL PF2 Value). * Trying to compile both lines and it's a total mess ! * BTW I noticed the problem doesn't occur if I'm using ROL for the 1st line and ROR with the 2nd (maybe a hint to find the cause of the problem ?) Does anybody can explain me where I'am wrong ??? I've join the source : the bug is located under the line 103 labeled : ;-------------- PROBLEM STARTS HERE-------------------- Thanks, Chris Yahoo! Mail : votre e-mail personnel et gratuit qui vous suit partout ! Créez votre Yahoo! Mail sur http://fr.benefits.yahoo.com/ Dialoguez en direct avec vos amis grâce à Yahoo! Messenger !Téléchargez Yahoo! Messenger sur http://fr.messenger.yahoo.com
Attachment:
Demo.asm
Description: Demo.asm
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