LISTING6.TXT

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**********************************************************************
*                                                                    *
*                68000 ASSEMBLER COURSE ON ATARI ST                  *
*                                                                    *
*                      by The Ferocious Rabbit (from 44E)            *
*                                                                    *
*                            Second series                           *
*                                                                    *
*                         Listing number 6                           *
**********************************************************************

         INCLUDE   "B:\START.S"
         
         MOVE.L    #MESSAGE,-(SP)    hello and clear screen
         MOVE.W    #9,-(SP)
         TRAP      #1
         ADDQ.L    #6,SP

         DC.W      $A000             A-line initialization

* Using A0 (return from function $A000) we get
* the address of the different arrays
* 4(A0) gives the address of the Contrl array
* 8(A0) gives the address of the Int_in array
* 12(A0) gives the address of the Ptsin array
* 16(A0) gives the address of the Intout array
* 20(A0) gives the address of the Ptsout array

         MOVE.L    8(A0),A3          save address of Int_in
         MOVE.L    12(A0),A4         save address of Ptsin

* We pass the coordinates of the point whose color we want
* Of course, we pass these coordinates in Ptsin.

         MOVE.W    #100,(A4)
         MOVE.W    #122,2(A4)
         DC.W      $A002             request color of a pixel

* Function $A002 returns the color of the pixel in D0, we then recolor
* another pixel with the color of the first

         MOVE.W    #100,(A4)
         MOVE.W    #123,(A4)
         MOVE.W    D0,(A3)           color of course in INT_IN
         DC.W      $A001             coloring of a pixel

         MOVE.W    #7,-(SP)          wait for key press
         TRAP      #1
         ADDQ.L    #4,SP
         MOVE.W    #0,-(SP)          and bye bye
         TRAP      #1
*---------------------------------------*
         SECTION DATA
MESSAGE  DC.B      "Pixel coloring with A-line",0

         SECTION BSS
         DS.L      100
PILE     DS.L      1
         END

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