In this tutorial, you can learn how to generate a 10Hz square wave using a timer in an 8051 microcontroller. I chose the AT89S51 microcontroller (You can select any other Keil-supported microcontroller) and demonstrated it. Generating a 10Hz square wave using a timer in an 8051 microcontroller is a common task. Here’s a basic tutorial on how to do it:
Generating a square wave is a fundamental task in electronics, often required for various purposes such as clock signals, digital communication, and waveform testing. One common way to generate a square wave is by using an astable multivibrator circuit, which typically consists of two transistors or integrated circuits like the 555 timer.
Contents
Required software
- Windows machine (Any Version)
- Keil IDE tool for 8051
- ProgISP v1.72
Required components and Programmer
- 1x AT89S51 Controller
- 1x 4Mhz Crystal
- 2x 22pf capacitor
- ISP AVR USB programmer
Note
Remember to configure the microcontroller’s clock frequency appropriately and adjust the timer values accordingly. Additionally, the exact implementation might vary depending on the specific variant of the 8051 microcontroller and the assembler you are using.
Code of 8051 Generating a 10Hz Square Wave
Assembly Code
- Configure Timer 0: Timer 0 is an 8-bit timer in the 8051 microcontroller. You need to configure it in mode 1 (16-bit mode) for generating square waves.
- Calculate Timer Value: Calculate the timer value needed to generate a 10Hz square wave. Timer value can be calculated using the formula: [ TimerValue = \frac{2^{16} – (RequiredCounts)}{CrystalFrequency} ] For a 10Hz square wave:
[ RequiredCounts = \frac{CrystalFrequency}{10} ] - Load Timer Value: Load the calculated timer value into Timer 0.
- Generate Square Wave: Configure Timer 0 in such a way that when it overflows, it generates an interrupt. Toggle a GPIO pin inside the interrupt service routine to generate a square wave.
- Repeat: The timer will continuously overflow, generating a continuous square wave.
ORG 0H ; Start of the program
MOV TMOD, #01H ; Timer 0, Mode 1 (16-bit mode)
MOV TH0, #0CH ; Load initial value for 10Hz frequency
MOV TL0, #0B0H ; (Assuming 11.0592 MHz crystal)
SETB TR0 ; Start Timer 0
MAIN: JMP MAIN ; Infinite loop
TIMER0_ISR:
CLR TF0 ; Clear Timer 0 overflow flag
CPL P1.0 ; Toggle GPIO pin P1.0
RETI ; Return from interrupt
ORG 0Hsets the origin of the code to address 0.TMODis configured for Timer 0 in mode 1.- Initial values for Timer 0 are loaded into
TH0andTL0. TR0is set to start Timer 0.- The main program is an infinite loop.
TIMER0_ISRis the Timer 0 interrupt service routine. It toggles the GPIO pin connected to P1.0.
C code
// www.aruneworld.com/
/// Tested By : Arun(20170227)
// Example Name : AEW_Blink_LED.lua
// Program to 10Hz_Square Wave generator at Port pin P1.0 (physical pin 1 of IC) using timer
#include <reg51.h> // special function register declarations for 89s51
#include<stdio.h> // prototype declarations for I/O functions
sbit pin = P1^0; // decleare a variable type sbit for P1.0
void main(void)
{
P1 = 0x00; // clear port
TMOD = 0x09; // (0x90->0b00001001) initialize timer 0 as 16 bit timer
loop: TL0 = 0xAF; // load valur 15535 = 3CAFh so after
TH0 = 0x3C; // 50000 counts timer 0 will be overflow
pin = 1; // send high logic to P1.0
TR0 = 1; // start timer
while(TF0 == 0) {} // wait for first overflow for 50 ms
TL0 = 0xAF; // again reload count
TH0 = 0x3C;
pin = 0; // now send 0 to P1.0
while(TF0 == 0) {} // wait for 50 ms again
goto loop; // continue with the loop
}
NEXT
| 8051 – Introduction |
| 8051 – Program Methods |
| 8051 – Flash HEX into 8051 |
| 8051 – USB ISP Programmer |
| 8051 – Simulators |
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| 8051 Interface – LED |
| 8051 Interface – LCD |
| 8051 Interface – 7 Segment |
| 8051 Interface – Keypad |
| 8051 Interface – Servo |
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| 8051 – UART Bit banking |
| 8051 – I2C Bit banking (Add Soon) |
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| 8051 – 10Khz Square Wave |
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| 8051 – Interview Questions |