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6502bench/SourceGen/Examples/Tutorial/Tutorial1.S
2018-09-28 10:05:11 -07:00

63 lines
1.2 KiB
ArmAsm

; 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
org $1000
ldy #END-AFTER
copy lda BEFORE,y
sta AFTER,y
dey
bmi done
bpl copy
dfb $00
stuff asc 'hello!'
done jmp AFTER
BEFORE
org $2000
AFTER
lda INPUT ;expecting 0-3
cmp #4
blt :valid
lda #4 ;error message
:valid asl A
tax
lda stringtab,x ;set load to address
sta _load+1
lda stringtab+1,x
sta _load+2
ldy #12 ;fixed-width strings
_load lda $0000,y ;self-modifying code
ora #$80
sta OUTPUT,y
dey
bpl _load
rts
stringtab
dw string0
dw string1
dw string2
dw string3
dw stringX
dfb $00
string0 asc 'string zero '
string1 asc 'string one '
string2 asc 'string two '
string3 asc 'string three '
stringX asc 'invalid index'
END