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how to solve a setup hold conflicting path

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preethi19

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can any1 tell plz how to solve a setup hold confliting path in the same corner. Normally for a setup path, one of the possibility is to skew the clock. Skewing clock is usually done at the capture flop CK pin. But I was suggested from my senior that another way is also that we can even borrow from the previous path (if there is enough margin). Its like cutting a point in the clk tree.. This would give enough margin for setup so then hold can be fixed. I didn't understand this part.. Can plz explain me.
 

preethi19 said:
can any1 tell plz how to solve a setup hold confliting path in the same corner. Normally for a setup path, one of the possibility is to skew the clock. Skewing clock is usually done at the capture flop CK pin. But I was suggested from my senior that another way is also that we can even borrow from the previous path (if there is enough margin). Its like cutting a point in the clk tree.. This would give enough margin for setup so then hold can be fixed. I didn't understand this part.. Can plz explain me.
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setup fix means to make the path faster or to allow more time for a slow path to compute. you can do buffering, logic restructuring, cloning, retiming, clock skewing... all of which could help. Your 'senior' was talking about retiming.
 

Borrowing is basically splitting your flop in positive level latch and negative level latch. Read about time borrowing and you will figure it out.
 

preethi19 said:
can any1 tell plz how to solve a setup hold confliting path in the same corner. Normally for a setup path, one of the possibility is to skew the clock. Skewing clock is usually done at the capture flop CK pin. But I was suggested from my senior that another way is also that we can even borrow from the previous path (if there is enough margin). Its like cutting a point in the clk tree.. This would give enough margin for setup so then hold can be fixed. I didn't understand this part.. Can plz explain me.
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HI Preethi,
How much violation you are seeing?
And how many paths?
What are setup/hold slacks?

Regards
Shareef
 

preethi19 said:
can any1 tell plz how to solve a setup hold confliting path in the same corner. Normally for a setup path, one of the possibility is to skew the clock. Skewing clock is usually done at the capture flop CK pin. But I was suggested from my senior that another way is also that we can even borrow from the previous path (if there is enough margin). Its like cutting a point in the clk tree.. This would give enough margin for setup so then hold can be fixed. I didn't understand this part.. Can plz explain me.
Click to expand...

Hi,
you are getting setup hold conflicting path because the end point in violation has two paths coming to the same end point - one with large path delay and the other with less path-delay passing through a common logic before ending into end-point. You need to trace the path upwards and find the common divergent path. from here, you need to fix the setup in large delay segment and hold in short delay segment.

Saket
 
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