What is the purpose of a Crystal oscillator?

Answer 1

Crystal oscillators are made of a piezoelectric material that vibrates at a very precise frequency. A crystal oscillator in a digital circuit is used primarily for generating a clock signal. A clock signal is a square-wave signal that goes between a maximum and minimum voltage (usually between 5V and 0V or between 3.3V and 0V) at a precise frequency generated by the crystal oscillator.

This clock signal is used for coordinating and/or controlling events in a digital circuit. In a digital watch, the current time is set and clock cycles are counted to measure the passage of time. As a second passes, the display is incremented to show that a second has passed. In a CPU, a program counter (which is used to keep track of which line of machine code the computer is at in a computer program) is incremented with each cycle of the clock. The faster the clock, the faster the program is executed. That is why CPU speed is measured in megahertz or gigahertz. There are other factors in program execution speed such as memory speed, read/write speeds, etc. but CPU clock speed is one of them.