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Text File  |  1996-12-24  |  2KB  |  88 lines
  1. *_____________________________*
  2. *                             *
  3. *       Mini-Scroll Plus      *
  4. *_____________________________*
  5. *                             *
  6. *   written by Bob Thrasher   *
  7. *     Copyright(c) 1988       *
  8. *     MicroSPARC, Inc.        *
  9. *     Concord, MA 01742       *
  10. *_____________________________*
  11. *                             *
  12. *   created with Merlin Pro   *
  13. *_____________________________*
  14. *                             *
  15.           ORG $0300
  16.  
  17. Source    EQU $26
  18. Dest      EQU $00
  19. Top       EQU $06
  20. Bottom    EQU Top+1
  21. Left      EQU Bottom+1
  22. Right     EQU Left+1
  23. Color     EQU $19
  24.  
  25. Up        LDX Top        ;Scroll up routine
  26. :1        TXA
  27.           TAY
  28.           INY
  29.           JSR Xfer
  30.           INX
  31.           CPX Bottom
  32.           BNE :1
  33.           RTS
  34.  
  35. Down      LDX Bottom     ;Scroll down routine
  36. :1        TXA
  37.           TAY
  38.           DEY
  39.           JSR Xfer
  40.           DEX
  41.           CPX Top
  42.           BNE :1
  43.           RTS
  44.  
  45. Clear     LDX Bottom     ;Clear a screen portion
  46. :1        TXA
  47.           PHA
  48.           LDY #$00
  49.           JSR $F411
  50.           PLA
  51.           TAX
  52.           LDY Right
  53.           LDA Color
  54. :2        STA (Source),Y
  55.           CPY Left
  56.           BEQ :3
  57.           DEY
  58.           BPL :2
  59. :3        CPX Top
  60.           BEQ :4
  61.           DEX
  62.           JMP :1
  63. :4        RTS
  64.  
  65. Xfer      STY YSAV
  66.           TXA
  67.           PHA
  68.           LDY #$00
  69.           JSR $F411
  70.           LDA Source
  71.           STA Dest
  72.           LDA Source+1
  73.           STA Dest+1
  74.           LDA YSAV
  75.           LDY #$00
  76.           JSR $F411
  77.           PLA
  78.           TAX
  79.           LDY Right
  80. :1        LDA (Source),Y
  81.           STA (Dest),Y
  82.           DEY
  83.           CPY Left
  84.           BGE :1
  85.           RTS
  86.  
  87. YSAV      EQU *
  88.