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109 lines
2.7 KiB
ArmAsm
109 lines
2.7 KiB
ArmAsm
;
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; 2003-04-13, Ullrich von Bassewitz
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; 2013-07-16, Greg King
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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
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.export setscrptr, cputdirect, putchar
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.constructor initcputc
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.import rvs
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.import popax
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.importzp ptr2
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.include "atmos.inc"
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_cputcxy:
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pha ; Save C
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jsr popax ; Get X and Y
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sta CURS_Y ; Store Y
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stx CURS_X ; Store 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 #$0D ; CR?
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bne L1
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lda #0
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sta CURS_X ; Carriage return
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rts
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L1: cmp #$0A ; LF?
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bne cputdirect
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inc CURS_Y ; Newline
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rts
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; Output the character, then advance the cursor position
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cputdirect:
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jsr putchar
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advance:
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iny
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cpy #SCREEN_XSIZE
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bne L3
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inc CURS_Y ; new line
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ldy #0 ; + cr
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L3: sty CURS_X
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rts
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; ------------------------------------------------------------------------
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; Set ptr2 to the screen, load the X offset into Y
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.code
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.proc setscrptr
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ldy CURS_Y ; Get line number into Y
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lda ScrTabLo,y ; Get low byte of line address
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sta ptr2
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lda ScrTabHi,y ; Get high byte of line address
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sta ptr2+1
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ldy CURS_X ; Get X offset
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rts
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.endproc
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; ------------------------------------------------------------------------
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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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.code
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.proc putchar
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ora rvs ; Set revers bit
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pha ; And save
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jsr setscrptr ; Set ptr2 to the screen
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pla ; Restore the character
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sta (ptr2),y ; Set char
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rts
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.endproc
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; ------------------------------------------------------------------------
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; Screen address table
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.rodata
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ScrTabLo:
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.repeat SCREEN_YSIZE, Line
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.byte <(SCREEN + Line * SCREEN_XSIZE)
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.endrep
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ScrTabHi:
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.repeat SCREEN_YSIZE, Line
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.byte >(SCREEN + Line * SCREEN_XSIZE)
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.endrep
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; ------------------------------------------------------------------------
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; Switch the cursor off. Code goes into the ONCE segment,
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; which will be reused after it is run.
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.segment "ONCE"
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initcputc:
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lsr STATUS
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asl STATUS ; Clear bit zero
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rts
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