about clock in digital circuit?

alfacliff

Joined Dec 13, 2013
2,458
usually with a crystal oscilator and several counters used as deviders. sometimes the o=scilator is seperate from the mcu, and sometimes it is internal. some older home clocks used the line frequency 50 or 60 hz to provide timing for the clock.
 

crutschow

Joined Mar 14, 2008
34,201
what is clock ? why it is necessery ? how to generate it?
Most complex digital circuits are sequential, where the logic is performed in discrete steps (such as a computer). A timing pulse signal (called a clock) is used to control the operational steps and keep all the circuitry in proper sequence. (An example of a common clocked circuit element is a flip-flip.) This clock is a digital pulse train and normally operates at a constant high frequency, limited only by the operational speed and propagation delay of the various circuit paths. The clock has to allow enough time for all the circuits to settle to their new state before the next clock arrives.

The clock can be generated by a simple RC relaxation oscillator, or by crystal oscillators if the frequency is critical to maintain an accurate time sequence for the logic outputs.
 

ScottWang

Joined Aug 23, 2012
7,397
>what is clock ?

A regular high low sequence as square wave.

>why it is necessary ?

It is like the heart for human, the heart compressing and pushing the blood, so we have a blood circulation in our whole body, and the same, the clock as the heart to pushing the high low signal to where they should go according to the designation.

>how to generate it?

google CD4069 oscillator, ne555 oscillator, crystal oscillator, and to see my blog.
 

MrChips

Joined Oct 2, 2009
30,621
There are two classes of digital circuits, combinational and sequential.

In a combinational circuit, the behaviour of the circuit is determined by input parameters.
For example, if there are four input parameters a, b, c, d, the output Q of the circuit can be expressed as a function of a, b, c, and d:

Q = f(a, b, c, d)

In a sequential circuit, the element of time and the current state of Q must be considered. Hence the next outcome of Q at time n+1 can be expressed as:

Qn+1 = f(a, b, c, d, Qn)

Thus the transition from Qn to Qn+1 is dependent on time. That is the purpose of the CLOCK signal. The CLOCK determines when the transition from one state to the next state occurs.
 

Thread Starter

Anikets

Joined Aug 6, 2014
15
Most complex digital circuits are sequential, where the logic is performed in discrete steps (such as a computer). A timing pulse signal (called a clock) is used to control the operational steps and keep all the circuitry in proper sequence. (An example of a common clocked circuit element is a flip-flip.) This clock is a digital pulse train and normally operates at a constant high frequency, limited only by the operational speed and propagation delay of the various circuit paths. The clock has to allow enough time for all the circuits to settle to their new state before the next clock arrives.

The clock can be generated by a simple RC relaxation oscillator, or by crystal oscillators if the frequency is critical to maintain an accurate time sequence for the logic outputs.
sir could you please tell me practical example for this?
 
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