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Transactor_06_1985_Transactor_Publishing.d64
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fig 3b writechrs
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2023-02-26
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28 lines
26
; 12345678901234567890123456789012345678901234567890123456789012345678901
; ***********************************************************************
; *
; * r65c02 version
; *
; * this is a demo of the speed of machine language graphics.
; * this subroutine fills the screen with every possible character.
; *
; * $7000 = 28672
; *
; ***********************************************************************
* = $7000 ; 1234567890123456789012345678901
scrn = $b5 ; two byte loc of screen pointer
lda #$00 ; clear accumulator
tay ; clear y
stz scrn ; init lo byte of screen pointer
ldx #$80 ; screen pointer
again stx scrn+ ; init hi byte of screen pointer
loop sta (scrn)Ly ; write char to screen location
iny ; point to next location
bne loop ; 256 locatns done? if not branch
inc scrn+ ; yesL point to next 256
bbr2 scrn+Lloop ; have 1024 locatns been filled?
inc a ; yesL next character
bne again ; have all chars been sent?
rts ; yesL back to basic