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PIC 16F877A output_b() problem

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John-Ove

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Hi all,

I am having some issues with the output_b() function.

I program the PIC 16F877A with output_b(255) which should put all port b pins on high level.

I tried 3 different PIC 16f877A and all of them had B3/PGM at low level.

I also tried the set_tris_b(0x00) before the output_b() method.

I have not used #use_fast_io() --> Is that something I would need?

John-Ove
 

I also tried the set_tris_b(0x00) before the output_b() method.
Click to expand...
Dear John
Hi
If you use set tris , method , it will set your pin ( or port ) as input or out put . if you set it as 0 it will be out put !
Follow below thing if you want that all of port B= out put and pin 3 at high level :
Set_tris_b(0)
out put _high ( pin_B3);
Best Wishes
Goldsmith
 

goldsmith said:
Dear John
Hi
If you use set tris , method , it will set your pin ( or port ) as input or out put . if you set it as 0 it will be out put !
Follow below thing if you want that all of port B= out put and pin 3 at high level :
Set_tris_b(0)
out put _high ( pin_B3);
Best Wishes
Goldsmith
Click to expand...

Hi...

Well.. I need to use the output_b(value), where value is an 8bit integer (0-255). This should set all the pins on port B either high or low depending on the integer value.
The problem is that no matter what value (between 0 & 255) the RB3/PGM pin is always low.

So if I enter: output_b(255); the pins on port B should all be at high level.

John-Ove
 

from page 45 of the datasheet:
"Low-Voltage ICSP Programming (LVP) is enabled by default which disables the RB3 I/O function. LVP
must be disabled to enable RB3 as an I/O pin and allow maximum compatibility to the other 28-pin and
40-pin mid-range devices."

make sure you enabled RB3
 
yuvko said:
from page 45 of the datasheet:
"Low-Voltage ICSP Programming (LVP) is enabled by default which disables the RB3 I/O function. LVP
must be disabled to enable RB3 as an I/O pin and allow maximum compatibility to the other 28-pin and
40-pin mid-range devices."

make sure you enabled RB3
Click to expand...

Hi,

Thank you for your reply.
Is it enough to set the fuses to NOLVP to enable the RB3?

Anyway.. I will check up on this when I get home..

John-Ove
 

HI John
Better try to using this fuses in your program, this may help u...

#fuses HS,NOPROTECT,NOPUT,NOCPD,NOLVP,NOWDT,NOBROWNOUT
 

you will also need to set the pin to output in TRISB, as goldsmith said
 

Hi All,

Thank you for the answers..
I got it working now.

The fuse needed was the NOLVP.

John-Ove
 

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