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polomint

MathsStuff

Jan 12th, 2022
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  1. ; MATH ZP LOCATIONS
  2. MATHWORKSPACE = &A0 ; 160d, START OF MATH ROUTINES WORKSPACE BLOCK
  3. ; MATH WORKSPACE BLOCK LAYOUT
  4. ;MATHWORKSPACE
  5.     MWS_INPUT1  = MATHWORKSPACE + 0      ; (b)
  6.     MWS_INPUT2  = MATHWORKSPACE + 1      ; (b)
  7.     MWS_INPUT3  = MATHWORKSPACE + 2      ; (b)
  8.     MWS_INPUT4  = MATHWORKSPACE + 3      ; (b)
  9.     MWS_OUTPUT1 = MATHWORKSPACE + 4     ; (b)
  10.     MWS_OUTPUT2 = MATHWORKSPACE + 5     ; (b)
  11.     MWS_OUTPUT3 = MATHWORKSPACE + 6     ; (b)
  12.     MWS_OUTPUT4 = MATHWORKSPACE + 7     ; (b)
  13.  
  14. ;
  15. ; ADD16
  16. ;   INPUT:  MWS_INPUT1 (w), MWS_INPUT3 (w)
  17. ;   OUTPUT: OUTPUT1 (w)
  18. .MATH_ADD16
  19. {
  20.     PHA
  21.     CLC
  22.     LDA MWS_INPUT1
  23.     ADC MWS_INPUT3
  24.     STA MWS_OUTPUT1         ; store sum of LSBs
  25.     LDA MWS_INPUT2
  26.     ADC MWS_INPUT4          ; add the MSBs using carry from
  27.     STA MWS_OUTPUT2         ; the previous calculation
  28.     PLA
  29.     RTS
  30. }
  31.  
  32.  
  33. ;
  34. ; SUBTRACT16
  35. ;   INPUT:  MWS_INPUT1 (w), MWS_INPUT3 (w)
  36. ;   OUTPUT: OUTPUT1 (w)
  37. .MATH_SUBTRACT16
  38. {
  39.     PHA
  40.     SEC                     ; set carry for borrow purpose
  41.     LDA MWS_INPUT1
  42.     SBC MWS_INPUT3          ; perform subtraction on the LSBs
  43.     STA MWS_OUTPUT1
  44.     LDA MWS_INPUT2          ; do the same for the MSBs, with carry
  45.     SBC MWS_INPUT4          ; set according to the previous result
  46.     STA MWS_OUTPUT2
  47.     PLA
  48.     RTS
  49. }
  50.  
  51.  
  52. ;
  53. ; MULTIPLY8
  54. ;   INPUT:  MWS_INPUT1 (b), MWS_INPUT2 (b)
  55. ;   OUTPUT: OUTPUT1 (w)
  56. .MATH_MULTIPLY8
  57. {
  58.     ; A * 256 + X = MWS_INPUT1 * MWS_INPUT2
  59.     PUSHAXY
  60.     LDA #$00
  61.     LDX #$08
  62.     CLC
  63. .m0
  64.     BCC m1
  65.     CLC
  66.     ADC MWS_INPUT2
  67. .m1
  68.     ROR A
  69.     ROR MWS_INPUT1
  70.     DEX
  71.     BPL m0
  72.     LDX MWS_INPUT1
  73.     ; store A, X in MWS_OUTPUT2, MWS_OUTPUT1
  74.     STA MWS_OUTPUT2
  75.     STX MWS_OUTPUT1
  76.     POPAXY
  77.     RTS
  78. }
  79.  
  80.  
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