Loud Speaker

( Membunyikan Loud Speaker / Palang Pintu Kereta Api )
$mod51
org 00h
jmp mulai
org 0bh
jmp hitung

hitung: cjne r5, #00h, maju
mov r5, #14
maju: dec r5
cjne r5, #00, exit
cjne r7, #50, maju2
mov r7, #00
maju2: inc r7
exit: reti

mulai: mov a, #00h
mov p0, #00h
mov p1, #00h
mov p3, #00h
mov r5, #20h
mov tmod, #81h
mov tcon, #00h
mov ie, #00h
setb ie.7
setb ie.1
setb tr0

loop: mov a, r7
jnb acc.0, nada1
acall beep2
nada1: acall beep
jmp loop

beep: mov r1, #150
ulang: dec r1 ;12 siklus
setb p0.0 ;12 siklus
cjne r1, #00h, ulang ;24 siklus
mov r2, #150
ulang2: dec r2
clr p0.0 ;12 siklus
cjne r2, #00h, ulang2
ret

beep2: mov r1, #200 ( Nilainya Semakin Kecil Frekuensinya Semakin Tinggi / Melengking )
ulang3: dec r1
setb p0.0
cjne r1, #00h, ulang3
mov r2, #200
ulang4: dec r2
clr p0.0
cjne r2, #00h, ulang4
ret
end