#71
#81
Help->Debug

@JohnInTX I am trying to simulate behavior of timer0 & mode1

1 tick take 1.085 us
100 * 1.085 = 108.5 us
65535 - 100 = 65435 ( 1111111110011011)
TH0 = 0xFF
TL0 = 0x9B

Timer will overflow at every 108.5 us

Program suppose to toggle port2 pin0 at each timer overflow

#include<reg51.h>

sbit PIN =  P2^0;

void main (void)  // Program start
{
    P0 = 0;
    P1 = 0;
    P2 = 0;
    P3 = 0;
 
    TMOD = 1;         //Timer mode1
   
      TH0 = 0xFF;      
    TL0 = 0x9B;
   
      TR0 = 1;          // Start timer0
   
      TF0 = 0;          // clear timer overflow flag
 
  while(1)
  {
       if (TF0 == 1)   // check Timer0 overflow flag
        {                      
           PIN =~ PIN;               // Toggle PIN P2^0 //                                                          
           TF0 = 0;                // clear Timer0 overflow flag
                   
                      TH0 = 0xFF;      
            TL0 = 0x9B;
         }
  }// while
}//main

 

'States' refers to internal CPU cycles. You can ignore that.
Time is shown on the status bar at bottom of the main window labeled 'sec'

 

Use the method in
https://forum.allaboutcircuits.com/...t-turning-off-8051-timers.172425/post-1547621

Time is about right for the way you’re using the timer.

 

Use the method in
https://forum.allaboutcircuits.com/...t-turning-off-8051-timers.172425/post-1547621

Time is about right for the way you’re using the timer.

I am trying to understand what happens when I set breakpoints at line 27. It appears that flag is set and LED is off at line 27

What's the time 9.96203?

 

It is your code, what do you think it is?
#61

 

It is your code, what do you think it is?
#61

Program : Turn ON LED when button will pressed

#include<reg51.h>

sbit LED = P2^0;
sbit Button = P3^7;

void Wait(int); //Function prototype declaration


void main (void)
{
  Button = 1; // Button PIN input
  LED = 0; //LED off initially

  while(1) //infinite loop
  {
    if(Button == 0 ) //If Button pressed
    {
            Wait(2000); //Delay
            if(Button == 0 ) //If Button pressed
            {             
        LED = 1; //LED ON
        Wait(2000); //Delay
        LED = 0; //LED OFF
  
      }         
        }
  }
}

void Wait (unsigned long int DelayTime)    /* Function to generate delay time */
{
    unsigned long int Count = 0;

    for (Count = 0; Count < DelayTime; Count++)
    {
        /* Do nothing */
    }
}

I think 2000 value gives 106401us (106ms) delay ?






@JohnInTX When I run program LED is ON for forever ?

 

Code is faulty. Debug it.

 

Code is faulty. Debug it.

#include<reg51.h>

sbit LED = P2^0;
sbit Button = P3^7;

void Wait (long unsigned  int DelayTime)    /* Function to generate delay time */
{
    unsigned long int Count = 0;

    for (Count = 0; Count < DelayTime; Count++)
    {
        /* Do nothing */
    }
}

void main (void)
{
  P0 =0x00;
    P1 =0x00;
    P2 =0x00;
    P3 =0x80;


  while(1) //infinite loop
  {
    if(Button == 0 ) //If Button pressed
    {
       Wait(1000); //Delay
         if(Button == 0 ) //If Button pressed
            {             
              LED = 1; //LED ON
              Wait(5000); //Delay
              LED = 0; //LED OFF
 
            }         
     }
  }
}

I don't understand why code stuck at line 26 in simulation

 

Program waits until Button input changes to zero, check Port 3 state

 

Program waits until Button input changes to zero, check Port 3 state

Have I corrected mistake ?

#include<reg51.h>

sbit LED = P2^0;
sbit Button = P3^7;

void Wait (long unsigned  int DelayTime)    /* Function to generate delay time */
{
    unsigned long int Count = 0;

    for (Count = 0; Count < DelayTime; Count++)
    {
        /* Do nothing */
    }
}

void main (void)
{
  P0 =0x00;
    P1 =0x00;
    P2 =0x00;
    P3 =0x80;


  while(1) //infinite loop
  {
    if(Button == 1 ) //If Button pressed
    {
       Wait(1000); //Delay
         if(Button == 1) //If Button pressed
            {             
              LED = 1; //LED ON
              Wait(5000); //Delay
              LED = 0; //LED OFF
 
            }         
     }
  }
}

 

Have I corrected mistake ?

#include<reg51.h>

sbit LED = P2^0;
sbit Button = P3^7;

void Wait (long unsigned  int DelayTime)    /* Function to generate delay time */
{
    unsigned long int Count = 0;

    for (Count = 0; Count < DelayTime; Count++)
    {
        /* Do nothing */
    }
}

void main (void)
{
  P0 =0x00;
    P1 =0x00;
    P2 =0x00;
    P3 =0x80;


  while(1) //infinite loop
  {
    if(Button == 1 ) //If Button pressed
    {
       Wait(1000); //Delay
         if(Button == 1) //If Button pressed
            {            
              LED = 1; //LED ON
              Wait(5000); //Delay
              LED = 0; //LED OFF

            }        
     }
  }
}

I don’t think so...I’m assuming/thinking that you are simulating the code. I.e., you haven’t wired up the hardware.

So, how are you simulating the button press? What do you do in the simulator to “press the button”?

 

What do you do in the simulator to “press the button”?

From #81 :

You can simulate what happens when an input bit changes by setting or clearing simulated bits in one of the Parallel Port windows that you have open.

Just a reminder for TS.

 

FWIW,
in #119:
Wait(1000) delays about 87ms
Wait(5000) delays about 424ms

As long as P3.7 is high, the LED will be ON about 424ms because of Wait(5000) and OFF about 87ms because of Wait(1000)
If P3.7 is low, the LED will stay OFF

It looks like Wait(1000) is part of a debouncer and as such shouldn't be used to time LED off. IMHO.

Good luck!

 

FWIW,
in #119:
Wait(1000) delays about 87ms
Wait(5000) delays about 424ms

As long as P3.7 is high, the LED will be ON about 424ms because of Wait(5000) and OFF about 87ms because of Wait(1000)
If P3.7 is low, the LED will stay OFF

It looks like Wait(1000) is part of a debouncer and as such shouldn't be used to time LED off. IMHO.

Good luck!

I think following code should be work but I don't understand why don't LED On/off 424ms when I press button ? why its stay on forever

#include<reg51.h>

sbit LED = P2^0;
sbit Button = P3^7;

void Wait (long unsigned  int DelayTime)    /* Function to generate delay time */
{
    unsigned long int Count = 0;

    for (Count = 0; Count < DelayTime; Count++)
    {
        /* Do nothing */
    }
}

void main (void)
{
  P0 =0x00;
    P1 =0x00;
    P2 =0x00;
    P3 =0x80;


  while(1) //infinite loop
  {
    if(Button == 0 ) //If Button pressed
    {
       Wait(1000); //debounce 87ms
         if(Button == 0) //If Button pressed
            {         
              LED = 1; //LED ON
              Wait(5000); //Delay for 424ms
              LED = 0; //LED OFF
              Wait(5000); //Delay for  424ms

            }     
     }
  }
}

Edit : We have pull up resistor that's why checking to 0

when I change if(Button == 1) into if(Button == 0) LED is continuously blinking ?

 

In #123 by inspection:
While button is 0, it will flash the LED 424ms ON and (424+87)ms OFF.
If button is 1, it will just hang on line 26 waiting for button == 0.

A quick turn through the simulator confirms this action.

 

Could you tell me what code will run on real hardware?

It should flash if the hardware is correct.

Schematic?

 

Check the button and LED are connected to right ports. Check MCU datasheet for output capabilities, are outputs push-pull or open collector type? Open collector output can only sink current.

 

The second sentence under Port3 heading says that it is a push/ pull (sink/source). Sink means switching to ground and source means switching to Vdd. If you want LED on by writing 1 to output then you should connect LED in series with resistor between output pin and ground.

To test MCU working state is simplest method to write simple LED flashing program. If it works it means MCUs clock is working and output is connected correctly. Then you can test programs with buttons.

 

Test button with simple program: if button pressed, turn LED on, else turn LED off. Then you can see if input works and in which level activates LED output.

 

Test button with simple program: if button pressed, turn LED on, else turn LED off. Then you can see if input works and in which level activates LED output.

I have done but I have not been successful yet #123