# Clock Concept

Discussion in 'Digital Circuit Design' started by LiamCorcy, Feb 14, 2019.

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1. ### LiamCorcy Thread Starter New Member

Feb 14, 2019
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Hello gentlemen ;
I've started working/learning new materials on digital logic devices and there's something getting me perplexed , when I've three digital devices connected sequentially to each other like this way: 1 2 3 which every number imply the order of the device, 1- is the first device ..etc . the devices are single cycle clock.

I didn't understand why the second device needs two clocks to get started and the third device needs three clock to get started? what's perplexing that the first clock enters to the first device so the first device will be operated .. and that clock will continue to the other device - the second one- and the second one will be operated .. and will also continue to the third device so the third device will be operated .. so how actually the second device needs two clocks to be operated ? the same with third device needs three clocks to be operated .. ? may please anyone illustrate me the concept of applying clocks on digital circuit and how it works when I've sequential digital devices?

In addition, if I send many clocks to the sequential device (( 1 2 3 )) so after three clocks the three I will get the required output .. but if I have many clocks what happened to the circuit ? will the output be periodic and repeated itself every three clocks?

2. ### ericgibbs Moderator

Jan 29, 2010
8,526
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hi Liam,
Welcome to AAC.
Do you have an actual example of the type of digital devices that you are querying.?
E

3. ### BR-549 AAC Fanatic!

Sep 22, 2013
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Can you show us a circuit example? Your description is hard to follow.

4. ### atferrari AAC Fanatic!

Jan 6, 2004
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Make sure the schematic is as much complete as possible.

If there are ICs involved, make sure they are properly identifiied.

5. ### LiamCorcy Thread Starter New Member

Feb 14, 2019
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0
Alright, I'm attaching it down ; but before, may please anyone explain how the clock is working here? I'm not understanding how every device has its own number of clocks, I mean for the first device here one clock is enough to start operate, for the second device two clock is enough to start operate, for the third device here three clock is enough to start operate ... I'm not understanding why? if the first device absorbs one clock then that same clock will go to the other devices and they also will be operated .. so why we need for instance two clocks to start with the second device?! I'm not understanding the point behind using clock at all.

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6. ### AnalogKid AAC Fanatic!

Aug 1, 2013
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Each flipflop has only one clock input, labeled Ck. One of the outputs of each stage is used as the clock input for the next stage. For each stage, there is a slight time delay between when the input clock happens and when the outputs change state, called the propagation delay. This means that all of the outputs do not go to their neat state at exactly the same time. They change sequentially from left to right. For that reason, this circuit is called a "ripple counter".

The J and K inputs are controls, not clocks. They tell the flipflop what action to take when the next clock edge happens. When the "High" input is high, the stages advance; when it is low, the outputs do not change. In this way, the High input acts as a counter enable signal.

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Last edited: Feb 14, 2019

Jan 29, 2010
8,526
1,713