How to avoid glitch in a logic that selects CLK or CLK_invert?

• Sep 28, 2005

• #1

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abhishek_elec

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I have a logic which selects CLK or CLK_invert based on a select signal.

If select = 1 then, o/p => CLK
else o/p => CLK_invert

When the clock switches from one to the other, what is the way to avoid the glitch.

 

• Sep 28, 2005

• #2

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AlexWan

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glitch removal

Hi abhishek_elec,

Please detail the information of relationship between two input clocks.

 

• Sep 28, 2005

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abdulsalam

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Re: glitch removal

are there any higher frequency clocks available.?

 

• Sep 28, 2005

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abhishek_elec

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Re: glitch removal

relationship of clocks is:

CLK_invert = not (CLK);


There are no other clocks available.

 

• Sep 28, 2005

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jjww110

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glitch removal

only if curent clock is slow and the next clcok is low , you can swtich.

 

• Sep 28, 2005

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abhishek_elec

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Re: glitch removal

jjww110,
this is not possible in this scenario. At any instant of time, both clocks are in opposite states to each other.
This kind of situation is very common in designs where u have to select either CLK or its invert based on some signal.
My question is , how do u switch such that there is no glitch ??

 

• Sep 28, 2005

• #7

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lcf0451

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Re: glitch removal

What is the relation of the select signal and the clock?

 

• Sep 29, 2005

• #8

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jjww110

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glitch removal

hi,abhishek_elec
sorry,i have not noticed the relation between two clocks,under this situation, i think this is not a good design and may change design to avoid it ,what's your comment?

 

• Sep 29, 2005

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abhishek_elec

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Re: glitch removal

jjww110,
I can't change the design. This type of clock selection does exist in many designs, this is not uncommon.

 

• Sep 29, 2005

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jjww110

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glitch removal

hi,abhishek_elec
you can mix posedge ff with negedge ff in your design, instead of swtich clock.

 

• Sep 29, 2005

• #11

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abhishek_elec

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Re: glitch removal

jjww110,
the requirement is to switch the clock at the run time. It;s not a static selection of clock. So while designing u can't determine which flops will clock at neg-egde and which at pos-edge.

 

• Sep 29, 2005

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abdulsalam

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Re: glitch removal

it would be helpful if you tell something more about your project

 

• Sep 29, 2005

• #13

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nemolee

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Re: glitch removal

Dear Sir,

I even discussed this topic. You can find it by searching "clock mux" this kind of key words. In this topic, you can also watch the related circuit for your reference.

Best Regards.

 

• Sep 30, 2005

• #14

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soccer

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glitch removal

i think your problem is focus on synchoronous.