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6502bench/SourceGen/Examples/Tutorial/Source/Tutorial2.S

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; Copyright 2018 faddenSoft. All Rights Reserved.
; See the LICENSE.txt file for distribution terms (Apache 2.0).
;
; Assembler: Merlin 32
INPUT equ $3000
OUTPUT equ $0400
PTR1 equ $02
PTR2 equ $04
START equ $2000
org START-2
dw START
sec
ror A
bmi skipstr
string0 asc 'first string',00
string1 asc 'another string',00
string2 asc 'string the third',00
string3 asc 'last string',00
skipstr
lda #<stringtab
sta PTR1
lda #>stringtab
sta PTR1+1
jsr thing
and #$03
asl A
tay
lda (PTR1),y
sta PTR2
iny
lda (PTR1),y
sta PTR2+1
ldy #$ff
]loop iny
lda (PTR2),y
beq copydone
ora #$80
sta OUTPUT,y
bne ]loop ;always taken
stringtab
dw string0
dw string1
dw string2
dw string3
copydone
jsr PrintInlineZString
asc 'Embedded!',00
lda #$ff ;self-modifying code example
sta _mod+1
_mod lda #$00
bne skipbrk
middat ds 4
outdat ds 1
skipbrk
lda middat ;nearby-label example
ora middat+1
and middat+2
eor middat+3
ldx #$00 ;embedded instruction example
dfb $2c
rebr ldx #$01
sta outdat
lda INPUT
lsr A
lsr A
lsr A
lsr A
sta INPUT
bne rebr
rts
thing
lda INPUT
rts
PrintInlineZString
pla
sta PTR1
pla
sta PTR1+1
ldy #$01
:loop lda (PTR1),Y
beq strend
ora #$80
jsr $FDED
iny
bne :loop
strend tya
clc
adc PTR1
sta PTR1
lda PTR1+1
adc #$00
pha
lda PTR1
pha
rts