synchronous and asynchronous clock

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SYNCHRONOUS AND ASYNCHRONOUS CLOCK

WHAT IS CLOCK ?

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A digital clock signal is basically a square wave

CLOCK....

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A clock is generated by clock generator.

here the clock generator is oscillator which provides the square wave as output.

clock will be having two levels…

high level (1) and low level (0).

CLOCK …(CONT’D)

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clock is used in the circuits which having feedback.

it is also is used to avoid glitches.

what is glitch?

glitch is unpredictable output.

some input and for those you expect a known output, but before the output settles to what you expect, you might have one or more transitions that are not suppose to be there. These are called glitches.

CLOCK….(CONT’D)

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CLOCK…(CONT’D)

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because the inputs have to go through different gates and the propagation delay of each can be different. Therefore the results arrive to the final gates in different times

This difference in data arrival results in changes in the output until all signals settle and the output is valid.

If glitches are not eliminated, they will go to the next stage of the circuit and generate more unpredictable results.

To avoid them a clock can be used to time the signals.

CHARACTERISTICS OF CLOCK

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There are two types of characteristics of clock are :

1. frequency , 2. phase .

TYPES OF CLOCK….

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there are two types of clocks….

synchronous clock.

Asynchronous clock

SYNCHRONOUS CLOCK…

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if two clocks have same phase and the frequency may or may not be same then that clock is called synchronous clock.

To decide it as a synchronous and asynchronous will not depend on the frequency.(because of frequency only speed varies). it will be decided by the phase of the two clocks.

if the source of two clock is same then the clock be synchronous.

SYNCHRONOUS CLOCK…

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if the source of the two clocks is different then is there is a chance of asynchronous.

ASYNCHRONOUS CLOCK…

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If the two clocks are with different phase and the frequency may or may not be same then the clock is known as asynchronous signal

If the source of the two clocks is different then there is chance of phase difference then it will leads to synchronous clock.

ASYNCHRONOUS CLOCK…

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CLOCK…(CONT’D)

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But due to this asynchronous clock there is chance of glitches.

So, for this we will synchronize the clock before going to process.

To make it as synchronous we use fifo (first in first out).

By avoiding the asynchronous we will get synchronous output and the complete circuit becomes the synchronous circuit.

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