; r0 - state
start:
    mov r0, 0
wait:
    jnb p1.1, maybe_n
    jnb p2.1, maybe_d
    sjmp wait
maybe_n:
    lcall delay
    jnb p1.1, n
    sjmp wait
maybe_d:
    lcall delay
    jnb p2.1, d
    sjmp wait
d:
    inc r0
n:
    inc r0
    mov a, r0
    add a, -3 ; add a, 253
    jnc ov, wait
    ; open door here
    sjmp start