How to init your circuit when power turned on?

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How to init your circuit when power turned on?

Post by admin » Wed Jun 17, 2009 10:19 am

If you have some state holding circuits in your circuit project like flip-flops you’ve probably noticed that when you turn power on they all flipped to some random state. Of course such flip-flops usually have a reset input and you want to send a reset signal to that input after the power gets on.
But how you can determine the moment when your circuit get powered? Well there is a hack to do this.
It is based on implementation of clock gate. So the clock gate always generates 1 after power turned on. So we can use this in order to catch an initial reset signal. Here is circuit you can use for this purpose.
PowerOnLatch.PNG
PowerOnLatch.PNG (4.29 KiB) Viewed 14052 times
It will generate 1 one cycle of clock right after you turn your project on and then it will flip to 0 indefinitely.

anders
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Re: How to init your circuit when power turned on?

Post by anders » Fri Mar 08, 2013 10:23 am

Can we have alternate circuit for power on reset. As it requires one AND Gate in the circuit, there are four logic AND Gates in an IC. We have to use 14pin IC for one AND Gate and we can reduce the layout space by using other small circuit.

circuit card assembly
Last edited by anders on Tue Jun 18, 2013 8:19 am, edited 3 times in total.

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Re: How to init your circuit when power turned on?

Post by admin » Fri Mar 08, 2013 11:11 am

I am afraid I do not quite understand you. Can you please rephrase you question?

strong
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Re: How to init your circuit when power turned on?

Post by strong » Thu Jul 06, 2017 5:34 pm

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I designed two or latch, one with or gate, and other one with transistors, but the one i designed with transistors wont work as expected.

I've tried and thought so much time to find bug but I couldn't !!!

Can anyone please tell me if it has a logical problem or "logisim" cause that problem ?

here is the image :

!http://imgur.com/a/B4p36

I used "logisim" app to create these circuits.

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Re: How to init your circuit when power turned on?

Post by admin » Tue Jul 11, 2017 11:38 am

Hi,
First of all if you want people see your questions try to create separate topic with clear title instead of adding your question to unrelated topic.
Second this forum mostly related to LogicCircuit program not logisim.
Finally, I am not sure what transistors are meant to be in logisim, but you can try to look at some other schematics like:
https://www.google.com/search?q=or+latc ... ransistors

Regards,
Eugene

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