Hi everyone,

my project is to switch on/off led one by one from P1,P3,P2,P0 with 1 seconde delay.

When i try my code, it's working very well on P1,P2 and P3 but for P0, the leds are blinking one by one and it never stops.
The portion of the code for Port 0 never exits.

here is the code:

 org 0000h
Loop:
mov p1,#00h
mov a,#01h
mov p1,a
mov p3,#00h
mov p2,#00h
mov p0,#0FFh

cpl a
L7:
rl a
mov p0,a
call delay
jb p0.7,L7
clr p0.7

Thank you very much if someone could help me,
ps: i use the 8051

 

You have not shown the full listing of your code.
Your code is incomplete.
Where does your code initialize the port direction register?
Where is delay?
How does the code loop back?

 

OK, here's the full code:

 org 0000h
Loop:
mov p1,#00h
mov a,#01h
mov p1,a
mov p3,#00h
mov p2,#00h

mov p0,#0FFh

lcall delay

;From P1.0 to P1.7
L1: 
rl a
mov p1,a
call delay
jnb p1.7, L1
clr p1.7
;From P3.0 to P3.7
mov a,#01h
mov p3,A
LCALL DELAY
L2:
rl a
mov p3,a
call delay
jnb p3.7, L2
clr p3.7
;From P2.0 to P2.7
L4:
rl a
mov p2,a
call delay
jnb p2.7,L4
clr p2.7


;From P0.0 to P0.7
cpl a
L7:
rl a
mov p0,a
call delay
jb p0.7,L7
clr p0.7


;-----------------------------------------
;Reverse From P0.7 to P0.0
cpl a
L8:
rr a
mov p0,a
call delay
jb p0.0,L8
clr p0.0


;Reverse From P2.7 to P2.0

L3:
rr a
mov p2,a
call delay
jnb p2.0,L3
clr p2.0
;Reverse from P3.7 to P3.0
L5:
rr a
mov p3,a
call delay
jnb p3.0,L5
clr p3.0
;Reverse from P1.7 to P1.0
L6:
rr a
mov p1,a
call delay
jnb p1.0,L6
clr p1.0

;--------------------
ljmp Loop
delay: mov r0,#14
m1:MOV TMOD,#01H ; initialise TMOD
MOV TL0,#76H ; initialise TL0
MOV TH0,#01H ; initialise TH0

SETB TR0 ; start timer
Wait: JNB TF0,Wait ; wait for TF0
; stop timer
CLR TF0 ; clear TF0
djnz r0,m1
ret
end

 

First you have jnb as your exit clause... But with P0 you are using jb

There is no need for LCALL as your code is small ( you have mixed "call delay" and "lcall delay") It isn't a problem... I just wondered

 

An 8051 does not have any "Port Direction Registers". When you write a 1 to the data latch it enables a weak pullup that makes it a quasi bi-directional pin.

Writing a 0 to the data latch makes it an open-drain output and disables the weak pullup.

 

Thank you
i replaced lcall by call, it was just a small mistake.
,tried to 0FFh or 00h to P0.
,replaced JB by JNB now the loop L7 exits but all leds are lit
i put VCC on the anode of P0 leds and the cathode directly to Port0

so the same problem exists
thank you

 

You can't hook LEDs directly to port pins. You need a current limiting resistor.

 

Yes i know but it's in the simulator (Proteus)
and i tried with resistor.

I think the problem is in the JB or JNB.


Thank you

 

i think we can't fix this problem with port0, so i will just avoid to use this port.
i asked to an expert around me, they can't recolve.

but i'm ready to try any other solutions

Thank you

 

Can you post me your schematic.... I'll have a go..

 

Here is the image of the schematics, i try to attach the .dsn file for proteus, it failed
Thank you

 

When i try my code, it's working very well on P1,P2 and P3 but for P0, the leds are blinking one by one and it never stops.
The portion of the code for Port 0 never exits.

here is the code:

 org 0000h
Loop:
mov p1,#00h
mov a,#01h
mov p1,a
mov p3,#00h
mov p2,#00h
mov p0,#0FFh

cpl a
L7:
rl a
mov p0,a
call delay
jb p0.7,L7
clr p0.7

The reason the program keeps looping on Port 0 is because port 0 has "open drain" outputs. You knew it and that's why you connected the LEDs to Vcc using Lo to light them. But the output pin is not low enough to be detected
as Logic Low without 10K pull-up resistors.

I simulated your circuit on proteus and though the LED did get lighted up but the logic on the pins are still at "Hi". Try pull up resistors parallel with your LED and the program should exit the loop.

Allen

 

Thank you so much absf, now the program exits from the loop.
i have to look for why leds do not light enough.
Your answer was usefull for me.

 

If the LED are too dim. Right-click on the resistor pack and change the property to "digital".

Allen

 

I tried to change the resistor's property from analog to digital but in digital, the program stay in the loop.
PY01A0080

 

Sorry absf, now it's working well.
i think i forgot to refresh windows or something like that.
It's perfect now, i know how to use the port0.
Thank you very much
PY01A0080

 

Always use pull up resistors with PORT0 of 8051. It doesn't have internal pull up circuit like other ports on it.

 

I think you have to connect a pull up register for Port 0. For the better understanding of Port 0 and the concept of pull up register, check this out.

https://www.youtube.com/watch?v=t9bN-2nFNEs