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The negative edge triggered FFs

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khaila

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The refernce of Setup/Hold Time in FFs with POSEDGE is the rising edge of its CLOCK.

But!!!
When we have FFs with NEGATIVE edge, what is the clock reference??? is it the rising edge or the negative edge???
 

ieropsaltic

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Re: FFs with Negedge!!!

If you mean by the reference is the edge for which to measure the setup and hold time, then for negative edge triggered FFs, you should use the falling edge .
 

    khaila

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nav_vlsi

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Re: FFs with Negedge!!!

The moment we say it as a negative edge triggered FF, Negative or falling edge of clock become the reference point, we have to measure both setup and hold time only with reference to this falling edge of clock
 

    khaila

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sanjay298

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Re: FFs with Negedge!!!

For the negative edge triggered FFs all the timing parameters are measured with reference to the falling edge or the negative edge of the clock
 

pilu.sandeep

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Re: FFs with Negedge!!!

For the negative edge triggered flipflops the setup and hold time analysis is done with respect to the falling edge of the clock.
 

damn

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Re: FFs with Negedge!!!

w.r.t to edge timing analysis. ha ha its simple
 

shiv_emf

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FFs with Negedge!!!

is thr any spl application for using -ve edge FF??

is thr any performance difference between +ve edge n -ve edge?
 

funster

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Re: FFs with Negedge!!!

it's negedge for negedge DFF's clock reference.




khaila said:
The refernce of Setup/Hold Time in FFs with POSEDGE is the rising edge of its CLOCK.

But!!!
When we have FFs with NEGATIVE edge, what is the clock reference??? is it the rising edge or the negative edge???
 

vinun_7

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Re: FFs with Negedge!!!

Normally during synthesis, the tool will invert the clock and still use a posedge flop.
Not sure whether all tools will do this every time. But seen this with synopsys power compiler.
 

spauls

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Re: FFs with Negedge!!!

tool will add inverter in clock path
 

phoenixfeng

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FFs with Negedge!!!

i agree with spauls
u need not to consider negative edge of clk, just using it when necessary
 

shaikss

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Re: FFs with Negedge!!!

Hi Buddy,
Its simple..
For -ve edge triggered flipflops, timing parameters setup and hold time are calculated w.r.t -ve edge or the falling edge of the clock
 

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