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Bill Lange

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Posts posted by Bill Lange


  1. Have these been archived?

     

    CX6009 A Side 1 Great Classics Caesar / Macbeth

    CX6009 A Side 2 Great Classics Ivanhoe / Treasure Island

    CX6009 B Side 1 Great Classics Mutiny / Two Cities

    CX6009 B Side 2 Great Classics Crusoe / Mohicans

    CX6009 D Side 1 Great Classics Musketeers / 20,000 Leagues

    CX6009 D Side 2 Great Classics Red Badge / William Tell

     

    post-188-0-25110400-1532630447_thumb.jpg post-188-0-75801800-1532630460_thumb.jpg

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  2. Hi folks. I know this is an incredibly old thread, but I am also going through the Atari Roots book and have a question about the code listed above. In particular, I'm confused about the .word directives right in the middle of the DL. Can someone please explain why that's there and what it does? It seems like it would totally mess up the display list. Thanks in advance!!

     

     

    0350 .BYTE $70,$70,$70,$70,$47; LMS, ANTIC MODE 7

    0360 .WORD LINE2; (TEXT LINE: "THE BIG PROGRAM")

     

    In line 350, the last byte, $47, is actually two nibbles. The "4" means LOAD MEMORY SCAN. The "7" means ANTIC MODE 7. The LOAD MEMORY SCAN is a 3-byte command. So typically, the $47 would be followed by a two byte address such as $47,$20, $7C ... with the data to be displayed beginning at address $7C20 ($20, $7C). In this case, line 360, says to look at the two byte address (a two byte .WORD instead of a one byte .BYTE) LINE2 to find the data to be displayed. It is just using a label instead explicit memory address to find the data to display.

     

    If you had pre-stored the data for the text string beginning at memory address $7C20, you could have deleted line 360 and just used

     

    350 .BYTE $70,$70,$70,$70,$47,$20,$7C

     

    The LOAD MEMORY SCAN just needs to know where the data to be displayed is. You can provide the address in different ways.

     

    Bill

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