chriscam

Hello, First, gotta say how happy I am that you all are here! You have totally inspired me to break out my old A800 and code binge. Thank you! Hopefully you will be kind to a newbie... I have many questions but I promise not to be annoying. Ok, so, I decided to take the plunge into assembly, and am both studying and assembling the following PMG example: Assembly Language Programming for the Atari Computers, by By Mark Chasin Chapter 10, http://www.atariarchives.org/alp/chapter_10.php The Problem: Clearing out the PM area of memory doesn't really clear anything, but rather stores alot of data: The offending code: ; ****************************** ; Now clear out PM area of RAM ; ****************************** LDY #0 ;use as counter LDA #0 ;byte to be stored CLEAR STA (XLOC),Y ;clear 1st byte DEY ;is page finished? BNE CLEAR ;page not done yet INC XLOC+1 ;page is done LDA XLOC+1 ;on to next page CMP STOTOP ;are we done? BEQ CLEAR ;one more page BCC CLEAR ;keep going When I remove the above section of code, everything appears normal, meaning my little tie fighter is drawn to the screen and there are no garbage bits elsewhere in the PM area. Since this code is right out of the book, I assume it was *reasonably* tested. So, I'm at a complete loss. Anyone know what could be going on? Best regards, Chris