Generating one second delay using internal timers of 8051(89c51,89c52) Microcontroller

In this tutorial i am going to teach you about how to generate one second delay using internal timer registers of 8051(89c51,89c52) series microcontrollers. Normally we use for-loops to generate delay. The delay generated by running loops is arbitrary. No fixed time delay is generated by loops. Loops are only suitable if you want an arbitrary delay in your program and not a proper fixed time delay. In order to generate proper delays you have to use the internal timers of 8051(89c51,89c52) microcontroller. 8051 series microcontrollers have two build in timers(Timer-0 & Timer-1). Each Timer is 16-bit wide. You can use them for generating delays, as counters and to generate baud rate for UART(Universal Asynchronous Receiver Transmitter) of microcontroller. In order to become familiarize with the internal register’s dedicated for timers and their functioning I recommend you to please first take a tutorial on

How to use internal timers of 8051 micrococntroller?

1 second delay with 8051 microcontroller – Diy project

I am going to blink an led after every 1 second using 89c51 microcontroller. 1 second delay is accurately generated by using the internal timers of 8051 micrococntroller. Below is a the code for blinking an LED(light emitting diode) after each second using 8051 microcontroller. Port-1 Pin#0 is declared as output and our led is connected to this pin. Code is very simple(If you are already familiar with the syntax of C-language used for 8051 series microcontrollers programming).

8051 microcontroller one second delay -Project code

First in code i included the header file <reg51.h>. reg51.h is the header file necessary to be included in every project which is using keil(software) for writing and compiling code. Then the statement sbit led=P1^0 is assigning Port-1 bit#0 a variable led.

Coming to main function. Statement P1=0x00 is initializing Port-1 as Output. Then led=1 is making our led to glow. delay() function is something that is the topic of this tutorial. led=0 is switching off our led after 1 second. This means led will glow for 1 second and then turn off for 1 second. Whole of this part is placed in while(1) loop making the Statements to execute for ever.

The main thing in the code is delay() function & how is it working? To understand it you should know about the internal timer registers and i hope you take the tutorial mentioned above. You can calculate the values for TH and TL registers by using the formula given in the tutorial. Also you will be able to know about the TMOD(Timer Mode) register bits. If you don’t go through the lesson then hurry up and take it

How to use internal timers of 8051 microcontroller for generating fixed delays.

Now if you took the tutorial you are thinking what’s going on in delay() function. Actually i calculated the delay values for 2 ms and loaded the calculated values for TH and TL registers in them.

One Second Delay generating with Internal Timer Registers of 8051(89c51,89c52)

Now if i run 2 ms delay for 500 times it will generate 1-Second Delay. The same thing is written in delay function. While loop is running for 500 times and generates 1 second delay. This 1 second delay can further be used to generate 1 minute delay.

Circuit diagram of the project is given below.

8051 microcontroller one second delay blink led

Project Circuit Diagram

In the while loop its not necessary to always initialize the TMOD, TH and TL registers. You can initialize these registers once in the main code and in the while loop you can only run and stop the timer using TR0 and TF0 interrupt flags. Again and again initialing the TMOD, TH and TL registers in while loop will increase the delay time by the factor of initialing the registers 500 times in each second.

I further generated one minute delay on the same principle listed above. You can also check out the project below. Source code of the project is also open source.

1 minute delay with timers of 8051 microcontroller

Download the Project Files & code(C, Hex) compiled in keil u Vision-4 and if have any questions regarding Post or Code. Write your Queries Below

Generating Fixed Delay Using Internal Timers of 89c51