!cpu    65816
*       =       $1000
        !as
        !rs
        jsr     L1006
        jmp     L1020

L1006   sep     #$30
        lda     $00
        beq     @L100F
        lda     #$00
        brk

@L100F  sta+3   $012345
        lda     $00
        beq     @L101A
        lda     #$00
        !byte   $85
@L101A  !byte   $8f
        eor     $23
        !byte   $01
        nop
        rts

L1020   !byte   $af