Dear ronan
see the code below
xtal:12Mhz

WITH INTERNAL LOOP YOU HAVE 50 msec delay
WITH SECOND LOOP YOU HAVE 100*50 msec=5 sec delay
WITH 3'd LOOP YOU HAVE 4*5=20 sec delay

and you can have another loop or higher value in R6,R7
for increasing delay.







MOV A,#1
START0:
MOV R6,#8
START1:
MOV P2,A
RL A
LCALL DELAY1
DJNZ R6,START1
SJMP START0


DELAY1:
PUSH 7
push 6
MOV R6,#4
STP1:
MOV R7,#100
STP0:
MOV TMOD,#00000001B
MOV TH0,#3CH
MOV TL0,#0B0H
SETB TR0
TF0?:
JNB TF0,TF0?
CLR TR0
CLR TF0
DJNZ R7,STP0
DJNZ R6,STP1
POP 6
POP 7
RET