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119 lines
2.8 KiB
ArmAsm
119 lines
2.8 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 06.08.1998
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;
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; void cputcxy (unsigned char x, unsigned char y, char c);
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; void cputc (char c);
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;
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.export _cputcxy, _cputc, cputdirect, putchar
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.export newline, plot
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.import popa, _gotoxy
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.include "pet.inc"
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_cputcxy:
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pha ; Save C
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jsr popa ; Get Y
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jsr _gotoxy ; Set cursor, drop x
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pla ; Restore C
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; Plot a character - also used as internal function
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_cputc: cmp #$0A ; CR?
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bne L1
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lda #0
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sta CURS_X
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beq plot ; Recalculate pointers
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L1: cmp #$0D ; LF?
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beq newline ; Recalculate pointers
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; Printable char of some sort
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cmp #' '
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bcc cputdirect ; Other control char
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tay
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bmi L10
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cmp #$60
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bcc L2
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and #$DF
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bne cputdirect ; Branch always
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L2: and #$3F
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cputdirect:
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jsr putchar ; Write the character to the screen
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; Advance cursor position
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advance:
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cpy SCR_LINELEN ; xsize-1
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bne L3
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jsr newline ; new line
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ldy #$FF ; + cr
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L3: iny
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sty CURS_X
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rts
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newline:
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lda SCR_LINELEN ; xsize-1
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sec ; Account for -1 above
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adc SCREEN_PTR
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sta SCREEN_PTR
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bcc L4
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inc SCREEN_PTR+1
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L4: inc CURS_Y
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rts
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; Handle character if high bit set
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L10: and #$7F
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cmp #$7E ; PI?
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bne L11
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lda #$5E ; Load screen code for PI
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bne cputdirect
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L11: ora #$40
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bne cputdirect
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; Set cursor position, calculate RAM pointers
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plot: ldy CURS_Y
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lda ScrLo,y
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sta SCREEN_PTR
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lda ScrHi,y
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ldy SCR_LINELEN
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cpy #40+1
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bcc @L1
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asl SCREEN_PTR ; 80 column mode
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rol a
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@L1: ora #$80 ; Screen at $8000
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sta SCREEN_PTR+1
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rts
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; Write one character to the screen without doing anything else, return X
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; position in Y
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putchar:
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ora RVS ; Set revers bit
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ldy CURS_X
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sta (SCREEN_PTR),y ; Set char
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rts
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; Screen address tables - offset to real screen
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.rodata
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ScrLo: .byte $00, $28, $50, $78, $A0, $C8, $F0, $18
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.byte $40, $68, $90, $B8, $E0, $08, $30, $58
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.byte $80, $A8, $D0, $F8, $20, $48, $70, $98
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.byte $C0
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ScrHi: .byte $00, $00, $00, $00, $00, $00, $00, $01
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.byte $01, $01, $01, $01, $01, $02, $02, $02
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.byte $02, $02, $02, $02, $03, $03, $03, $03
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.byte $03
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