Square Wave Generation Using PIC16F877

by
Square Wave Generation Using PIC16F877 2

Square Wave Generation Using PIC16F877: In this post ,the methods of square wave generation using PIC16F877 Micro controller is explained. The applications of square wave also listed. Programming of PIC16F877 for sqaure wave generation also can be read in another post, will link it HERE.

Methods of square wave generation


A square wave is a periodic waveform that alternates between two voltage levels (logic HIGH and LOW) with a 50% duty cycle in the simplest case. It is widely used in clock signals, digital timing, switching circuits, and waveform generation.


The PIC16F877 microcontroller can generate a square wave using two main approaches:

  1. Software delay method – toggling an I/O pin in a loop with delay routines.
  2. Hardware timer/PWM method – using on-chip timers and CCP (Capture/Compare/PWM) modules for accurate waveform generation.

(a) Software Delay Method


• Any digital output pin (e.g., RB0) can be set HIGH and LOW alternately in program code.
• Delays are introduced between transitions to control frequency.
• Simple, but frequency depends on instruction execution time and is less precise.
Frequency formula:
f=12⋅Tdelayf = \frac{1}{2 \cdot T_{delay}}f=2⋅Tdelay1
where TdelayT_{delay}Tdelay is the software delay used.

(b) Timer-Based Method


• PIC16F877 has Timer0, Timer1, and Timer2 which can generate periodic interrupts.
• The interrupt service routine (ISR) toggles an output pin → square wave output.
• This method gives better accuracy compared to software delays, since timers run with the oscillator clock.
Half-period time:
Thalf=(Prescaler×(256−TMRx_preload))×TcyT_{half} = (Prescaler \times (256 – TMRx_preload)) \times T_{cy}Thalf=(Prescaler×(256−TMRx_preload))×Tcy
where Tcy=4FoscT_{cy} = \frac{4}{F_{osc}}Tcy=Fosc4.

(c) PWM Using CCP Module


• The CCP (Capture/Compare/PWM) module can directly generate a square wave on CCP1 pin (RC2).
• By setting duty cycle to 50%, a symmetric square wave is obtained.
• Frequency is controlled by Timer2 and PR2 register.
PWM frequency formula:
fPWM=Fosc4⋅N⋅(PR2+1)f_{PWM} = \frac{F_{osc}}{4 \cdot N \cdot (PR2+1)}fPWM=4⋅N⋅(PR2+1)Fosc
where
• FoscF_{osc}Fosc = oscillator frequency,
• NNN = Timer2 prescaler,
• PR2 = period register.

Square Wave Generation Using PIC16F877
Square Wave Generation Using PIC16F877

Applications of Square Wave Using PIC16F877


• Generating clock pulses for other circuits.
• Driving stepper motors and DC motors (PWM speed control).
• Producing tones in buzzers.
• Carrier signal generation in communication.
• Timing and synchronization in embedded systems.

Advantages of Using PIC for Square Wave


• Multiple frequency ranges (software, timer, PWM).
• High accuracy with hardware timers.
• Minimal CPU load when using CCP PWM.
• Easy frequency adjustment via register values.

Read Also on PIC PIC16F877

  1. PIC16F877

More on Microcontrollers

  1. Features of AVR|AVR Microcontrollers
  2. 8051 ARCHITECTURE|8051 Microcontroller Architecture
  3. 8051 Microcontroller Architecture|RISC and CISC CPU Architectures|HARVARD & VON- NEUMANN CPU Architecture
  4. Microprocessor VS Microcontroller| Comparison of Microprocessor and Microcontroller|Difference between Microprocessor and Microcontroller
  5. Addressing modes of 8051 Microcontroller|8051 Addressing Modes
  6. 8051 Microcontroller Instruction Set|KSEB Sub Engineer Notes
  7. 8051 Microcontroller MCQ|8051 Questions and Answers
  8. Microcontroller|Types of microcontroller
  9. 8051 Microcontroller Notes pdf|8051 microcontroller pdf
  10. Interrupts in 8051|Interrupts in 8051 Microcontroller

Join EEE Made Easy Whatsapp Channel

Join EEE Made Easy Telegram channel

Download EEE Made Easy Ebook PDF Free

Latest Posts in EEE Made Easy

Leave a Comment