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C program Time delay help!

Bill Thompson over 11 years ago

Dear sirs and madams

I present the following program to which i am simulating on a 8051 MCU

#include <reg51.h>

#include <stdio.h>
#define output P0

void main ()
{ unsigned int x;

while(1) { output = 1;

for(x=0; x<65000; x++) {

}

output = 0; for(x=0; x<65000; x++) {

}

My problem is that i am attempting to learn timing delays. For this program the P0 goes from 0 to 1 with a delay between. When i debug the program and run it with peripheral P0 open, it switches the value from 0 to 1 BUT the problem is its going to fast no matter how much delay i am putting in.

Please help me

Parents

0 Elvis Simmons over 11 years ago in reply to ImPer Westermark

I think you should look at your P0 access. Do you realise you're accessing 8 bits?

For your timing, the following might be worth some experimentation:

#include <reg51.h>

#include <stdio.h>

#include <intrins.h>

#define output P0

void main ()
{
  unsigned int x;

  while(1)
  {
    output = 1;

    for(x=0; x<65000; x++)
    {
      _nop_();
    }

    output = 0;

    for(x=0; x<65000; x++)
    {
      _nop_();
    }
}

Reply

0 Elvis Simmons over 11 years ago in reply to ImPer Westermark

I think you should look at your P0 access. Do you realise you're accessing 8 bits?

For your timing, the following might be worth some experimentation:

#include <reg51.h>

#include <stdio.h>

#include <intrins.h>

#define output P0

void main ()
{
  unsigned int x;

  while(1)
  {
    output = 1;

    for(x=0; x<65000; x++)
    {
      _nop_();
    }

    output = 0;

    for(x=0; x<65000; x++)
    {
      _nop_();
    }
}

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