Write a short note on oscillator circuit.

Subject : Embedded Systems Design

Topic : Fundamentals of Embedded System

Difficulty level : Low

1 Answer
  • Clock pulses are required any digital systems. Microprocessor embedded system digital system. Some microcontrollers have on chip oscillator circuit and require only a crystal to be connected externally, while some require external oscillator circuit.
  • 8051 has an on chip oscillator but needs and external clock to run it.
  • The oscillator circuit generates the clock pulses so that all the internal and external operations are synchronized.
  • The pins XTAL1 & XTAL2 are used to connect crystal. The Crystal is always connected along with the capacitors as shown in figure.
  • 8051 microcontroller are available in market with varying range of operation from 1MHz to 16 MHz
  • Generally 11.0592 MHz crystal oscillators are used so that the 8051 microcontroller systems are compatible with the serial port.
  • One machine cycle comprises of 12 oscillator periods. Hence to find the time for one machine cycle we need to consider 1/12th of Crystal frequency.

    Oscillator Circuit

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