Revision as of 11:56, 22 August 2016

In this tutorial, we are going to discuss the Timer module of 8051.
First, we will see what are timers, their working and later we will configure the 8051 timers to generate the delay of 100ms and 500ms respectively. At the end, we will see how to use the ExploreEmdedded Timer library.

Timer Basics

As the name suggests these are used to measure the time or generate the accurate time delay. The microcontroller can also generate/measure the required time delays by running loops, but the timer/counter relieves the CPU from that redundant and repetitive task, allowing it to allocate maximum processing time for other tasks.

The timer is nothing but a simple binary counter that can be configured to count clock pulses(Internal/External). Once it reaches the Max value, it will roll back to zero setting up an OverFlow flag and generates the interrupt if enabled.

8051 Timer Module

8051 has two indepenndent timer which can be used as timer,Counters.
Below table provides the details of the 8051 Timers.

Video Tutorial

Timer Basics

Generating 50ms Delay with Timer 0, Mode 1

Timer Operation

fig 1:Basic Timer

Timer Tick

Timer Registers

Timer Register T0/T1

TMOD Register

TCON Register

fig 2:Mode 0

fig 3:Mode 1

fig 4:Mode 2

Timer Example

#include<reg51.h>
void delay_t0(void);// function prototype
 
void delay_t0()
{
   TMOD = 0x01; //Timer zero mode 1  
   TH0 = 0X4B; 
   TL0 = 0XFF;
   TR0 = 1; //turn ON Timer zero
   while(TF0 == 0);
   TF0 = 0; //clear the timer
   TR0 = 0;
}
void main()
{
  P3 = 0x00; //set port as output  
  while(1)
  {
   P3 = 0XFF;
   delay_t0();
   P3 = 0X00;
   delay_t0();
  } 
}

PREVIOUS TUTORIAL

NEXT TUTORIAL

{{#seo: |title=8051_Timers |titlemode=append |keywords=8051,AT89s51,at89c51,p89v51rd2,XploreLabz,Timer,Timers,8051 timers/counters,8051 timer operation,8051 Timer registers,TMOD Register,TCON register |description=8051 Timers }} Would like to have your feedback and suggestions here;