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whisper
Visitor
Visitor
12,716 Views
Registered: ‎04-07-2014

Get a gate delay in xilinx (verilog)

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Hello,I am a Xilinx beginner

And I already get the gate delay in my program

But I have some question about why the delay time was not bigger than (9.157*3)ns

I have call the module "Look ahead adder "three time, but why?

 

program:

 

Program LM.PNG

 

module Look_Ahead_Adder's delay:

 

Timing Detail LA.PNG 

 

moudle Look_Ahead_Multiplier's delay:

Timing Detail LM.PNG

 

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gszakacs
Instructor
Instructor
20,793 Views
Registered: ‎08-14-2007

The total delay being reported is from pad to pad.  If you look at the details, a large portion of this (about 4.5 ns) is actually delay through the input and output buffers.  Adding another module in series does not add more input or output buffers, so the additional delay will be smaller.  Also note that routing delays can be larger than logic delays, especially if your input and output pins are not located near eachother.

 

And by the way it's not a "program" but a hardware description.

-- Gabor

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gszakacs
Instructor
Instructor
20,794 Views
Registered: ‎08-14-2007

The total delay being reported is from pad to pad.  If you look at the details, a large portion of this (about 4.5 ns) is actually delay through the input and output buffers.  Adding another module in series does not add more input or output buffers, so the additional delay will be smaller.  Also note that routing delays can be larger than logic delays, especially if your input and output pins are not located near eachother.

 

And by the way it's not a "program" but a hardware description.

-- Gabor

View solution in original post

whisper
Visitor
Visitor
12,368 Views
Registered: ‎04-07-2014

Appreciate your answer

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pulim
Xilinx Employee
Xilinx Employee
12,351 Views
Registered: ‎02-16-2014

Hi Whisper,

 

If the gabor's post answered your question please close the thread by marking the post as accepted solution.

This is good forum practice and it will help the other forum users also.

 

Thanks,

Manusha.

 

 

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whisper
Visitor
Visitor
12,318 Views
Registered: ‎04-07-2014

Thank you for your suggestion

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