Strange PIC problem as I can't get the output from port b

hi
I am trying to code a simple program like this
W equ 00h
STATUS equ 03h ;Address of the STATUS register
TRISB equ 86h ;Address of the tristate register for port A
PORTB equ 06h ;Address of Port A

;****Set up the port****

bsf STATUS,5
movlw 00h ;Set the Port A pins
movwf TRISB ;to output.
bcf STATUS,5
Start
movlw b'11111111'
movwf PORTB
goto Start
end
I am programming using a jdm programmer and the pic gets verified correctly.
but when i put it in breadboard i am not getting an o/p from port b. I hvae checked everything and tried changing parts also in the circuit.
i have previously used this programmer succesfully on many programs
I cant understand wht is wrong this time

Strange PIC problem

Firstly use an include statement instead of manually defining the registers.
Secondly which PIC are you using? Do you have a crystal (assuming it needs one)

Re: Strange PIC problem

Start
movlw b'11111111'
movwf PORTB
goto Start
end

Click to expand...

1. You have mentioned that you are not getting an output. If the PIC is executing the code, the o/p will always be high as per your code.
2. If you have enabled WDT in the configuration fuses, the watchdog will reset the PIC since you are not clearing the WDT.

Cheers

Ravi

Strange PIC problem

1. i will try the include statement and come back
2. yes i use a crystal i set it in icprog when programming the pic
3. i used PIC16F84A and PIC16F870
4. The output is that PortB Pin shd be high. But I dont get anything in PORTB Pins
5. i have disabled WDT in icprog.

Added after 11 minutes:

I tried the include option but to no avail
here is the new code
#include<C:\Program Files\Microchip\MPASM Suite\P16F84A.INC>
bsf STATUS,5
movlw 00h
movwf TRISB
bcf STATUS,5
Start
movlw b'11111111'
movwf PORTB
goto Start

end
and here is the hex file
:020000040000FA
:0E0000008316003086008312FF30860004282D
:00000001FF

Re: Strange PIC problem

Your program is working fine on PIC Simulator with the posted new code


hex code :

Assebly listing:

try the hex i provided since it differs from your post

Hope this helps

Nishal

Re: Strange PIC problem

tijoseymathew said:

1. i will try the include statement and come back
2. yes i use a crystal i set it in icprog when programming the pic
3. i used PIC16F84A and PIC16F870
4. The output is that PortB Pin shd be high. But I dont get anything in PORTB Pins
5. i have disabled WDT in icprog.

Click to expand...

One issue, check if the oscillator is actually oscillating. At 4MHz, you should be able to check with a scope.

Cheers

Ravi

Re: Strange PIC problem

tijoseymathew said:

hi
I am trying to code a simple program like this
W equ 00h
STATUS equ 03h ;Address of the STATUS register
TRISB equ 86h ;Address of the tristate register for port A
PORTB equ 06h ;Address of Port A

;****Set up the port****

bsf STATUS,5
movlw 00h ;Set the Port A pins
movwf TRISB ;to output.
bcf STATUS,5

Click to expand...

I highlighted your line above. The address 00h occupied by INDF register and cannot be assigned to other file.

On the other hand, your code does not change status of the output port pins.

Re: Strange PIC problem

nguyennam said:

tijoseymathew said:

hi
I am trying to code a simple program like this
W equ 00h
STATUS equ 03h ;Address of the STATUS register
TRISB equ 86h ;Address of the tristate register for port A
PORTB equ 06h ;Address of Port A

;****Set up the port****

bsf STATUS,5
movlw 00h ;Set the Port A pins
movwf TRISB ;to output.
bcf STATUS,5

Click to expand...

I highlighted your line above. The address 00h occupied by INDF register and cannot be assigned to other file.

Click to expand...

No, if you declare it in the source code or not, W has the value of 00.

It is implemented as follows ---> movf counter,w

You can use movf counter,0 ... it still remains the same.

On the other hand, your code does not change status of the output port pins.

Click to expand...

The original issue is that the output DOES NOT go high. The code is ok. It runs well on the simulator.

Please check the oscillator to see if it is running. Device could be ok but the crystal or capacitor could be bad.

Cheers

Ravi

Re: Strange PIC problem

nguyennam said:

The address 00h occupied by INDF register and cannot be assigned to other file.

Click to expand...

W equ 00h ... isn't adress, it is constant, and this definition is in all original Microchip Pxxxx.inc files.
This isn't error.

Re: Strange PIC problem

Try this. It has the __CONFIG and LIST directives plus the important and missing ORG statement and it does work with a 4MHz crystal.

Re: Strange PIC problem

Hi check the following is your TOCKI and MCLR pulled high? on bread boards it is always a good move to place a 10mf cap directly between Vss and Vdd, I always use a 10mf 16v tant across the chip as close to the 2 pins as possible