Help needed on 8051 programming

[ClouDxv1]

Im writing a programme for my Atmel 89S51.
But i cant seem to get it right. As u can see frm the picture, i can jump to SWITCHON when P2.1 is grounded but i cant jump to SWITCHOFF when P2.2 is grounded.
Can anyone help me pls... this is urgent its for my FYP
Thx


**broken link removed**

FYI this is a simple programme i wrote for testing purpose.. but i cant get it working nicely.

 

[vibeeshpv]

make u r P2 port as in put for that u just give 0xff value to the port
mov p2,#0ffh

k...all de best

 

[Hero]

Hi,

8051 IO ports are bidirectional. To read from port you need to configure port for reading first. To do this you need to write 0xff to port or 1 to selected bit of port.

Another possible problem is bad physical connection.

 

[ClouDxv1]

Hi,

8051 IO ports are bidirectional. To read from port you need to configure port for reading first. To do this you need to write 0xff to port or 1 to selected bit of port.

Another possible problem is bad physical connection.

Thx for the replies..
how to i write 0xff to the ports?
Sorry im still a beginner in this programming on 8051

 

[IanP]

Try the following code:

                       1    $NOPAGING
                       2    $MOD252
                       3    
0000                   4                    ORG     0000h
                       5    
0000 75A0FF            6                    MOV     P2, #0FFh
                       7    
0003 759000            8    START:          MOV     P1, #00000000b
0006 30A102            9                    JNB     P2.1, SWITCH_ON
0009 80F8             10                    JMP     START
                      11    
000B 7590F8           12    SWITCH_ON:      MOV     P1, #11111000b
000E 30A2F2           13                    JNB     P2.2, START
0011 80F8             14                    JMP     SWITCH_ON
                      15    
                      16                    END

VERSION 1.2h ASSEMBLY COMPLETE, 0 ERRORS FOUND
P1 . . . . . . . . . . . . . . .  D ADDR  0090H  PREDEFINED  
P2 . . . . . . . . . . . . . . .  D ADDR  00A0H  PREDEFINED  
START. . . . . . . . . . . . . .  C ADDR  0003H  
SWITCH_ON. . . . . . . . . . . .  C ADDR  000BH

Regards,
IanP

 

[budhy]

Aftar reset P0, P1,P2 & P3 is automatically set to 0xFF, it mean all port are as input already!

JNB P2.2,SWITCHOFF
i cant jump to SWITCHOFF when P2.2 is grounded.

it mean P2.2 always in 'high' position, even you ground it!

As Hero said :

problem is bad physical connection

check P2.2 volatge when you turn on/off your switch

 

[ClouDxv1]

Try the following code:

                       1    $NOPAGING
                       2    $MOD252
                       3    
0000                   4                    ORG     0000h
                       5    
0000 75A0FF            6                    MOV     P2, #0FFh
                       7    
0003 759000            8    START:          MOV     P1, #00000000b
0006 30A102            9                    JNB     P2.1, SWITCH_ON
0009 80F8             10                    JMP     START
                      11    
000B 7590F8           12    SWITCH_ON:      MOV     P1, #11111000b
000E 30A2F2           13                    JNB     P2.2, START
0011 80F8             14                    JMP     SWITCH_ON
                      15    
                      16                    END

VERSION 1.2h ASSEMBLY COMPLETE, 0 ERRORS FOUND
P1 . . . . . . . . . . . . . . .  D ADDR  0090H  PREDEFINED  
P2 . . . . . . . . . . . . . . .  D ADDR  00A0H  PREDEFINED  
START. . . . . . . . . . . . . .  C ADDR  0003H  
SWITCH_ON. . . . . . . . . . . .  C ADDR  000BH

Regards,
IanP

Thx for the reply.
But i use the code u giv me and load it into the MC but it still cant jump to START when P2.2 is grounded

 

[budhy]

But i use the code u giv me and load it into the MC but it still cant jump to START when P2.2 is grounded:

I am sure it is a hardware problem.
Onece again : check P2.2 volatge when you turn on/off your switch

 

[IanP]

If you are sure that P2.2 is properly grounded and P2.1 is not grounded at the same time (if it is, you will have square wave on P1.7, .. , P1.3) and the micro doesn't want to go to START, then try another pin, say, P2.3 ..
Maybe, although very unlikely, P2.2 is damaged for some reasons ..

Regards,
IanP

 

[ClouDxv1]

I've check the voltage on P2.2 it shows only 0.02v while the rest of the ports shows reading of 4.97v.
So that means my P2.2 is spoilt?

 

[budhy]

Don't use P2.2 any more, try with all other pin except P2.2

 

[adnan_wns]

use pull up resistor

 

[budhy]

use pull up resistor

Sorry adnan_wns, P2 has internal pull up already!