IntHandler:
    jp  (iy)

Gray1:
    exx
    ex  af,af'
    ld  a,(hl)
    inc l
    xor (hl)
    and c
    xor (hl)
    inc hl
    out ($11),a
    ex  af,af'
    exx
    .db $FD
    ld  l,Gray2
    ret

Gray2:
    exx
    ex  af,af'
    ld  a,(hl)
    inc l
    xor (hl)
    and d
    xor (hl)
    inc hl
    out ($11),a
    ex  af,af'
    exx
    .db $FD
    ld  l,Gray3
    ret

Gray3:
    exx
    ex  af,af'
    ld  a,(hl)
    inc l
    xor (hl)
    and e
    xor (hl)
    inc hl
    out ($11),a
    ex  af,af'
    exx
    .db $FD
    ld  l,Gray1
    ret