Writing to a PORT does not change its state

Asked Apr 23 '16 at 08:16

Active Apr 23 '16 at 15:07

Viewed 231 times

I have the following program - Using XC8 C Compiler on MPLAB and the microcontroller is PIC16F877.

int main()
{
  TRISB = 0x00;
  while(1)
  {
    PORTB = 0xFF;
    __delay_ms(1000);
    PORTB = 0x00;
    __delay_ms(1000); 
  }
  return 0;
}

I have LED connected to the output pins of PORTB. BUT there is no blinking.

However, when I do this on individual pins, it works perfectly: Eg:

RB0 = 1;
RB1 = 0;
RB2 = 1;

What am I doing wrong?

asked Apr 23 '16 at 08:16

Nujufas

1

Try writing 0x07 and 0x00 to PORTB instead of 0xFF. – Swanand Apr 25 '16 at 12:25
Did you check visually or with an oscilloscope ? If something is wrong with the timing it might blink too fast. – Marco van de Voort Jul 12 '17 at 09:22
1

Possibly over current? Have you tried setting all your PORTB on with the individual flags? Ex. `RB0 = 1; RB1 = 1; RB2 = 1; ...` – Mathieu L. Mar 07 '18 at 13:52
try to disable the comparators to get sure they are really off. For me it solved a simular problem. – Mike May 03 '19 at 11:33

0 Answers0