What is timing in P&R ?

I see many places "we have to meet the timing " while doing P&R.

Can someone please explain me :
1. What is timing as related to P&R
2. Where the timing info is set
3. What are the min timing requirements that need to be met.
4. What if we don't get the required timing ?

Thanks
Disney

Re: What is timing ?

HI Disney,

Timing is a very important aspect in chip design.Meeting the timing means "whether our design meets the required operating frequeny or not apecified according to the specifications"

People are very concerned at every stage in the design about timing bcoz as we as we proceed in the design stage the timing gets deteriorated bcoz of unwanted parasitics.

during the synthesis stage itself we give some timing constraints(SDC) conveying the tool not to violate the constraints so that we can can meet the timing.So like this at every stage we have procedures to make sure the timing is met(i.e design is working at required operating frequency)

Re: What is timing ?

Can someone help me in understanding other timing related questions

Thanks
Disney

Re: What is timing ?

1. What is timing as related to P&R
-- Placement decides location of each instances
-- CTS decides the clock networks
-- Routing decides wire of each interconnects
--> Parasitic RC is decided by P&R.

Therefore, there are timing-driven Placement & timing-driving routing.
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2. Where the timing info is set
-- In most case, timing constraints are defined in the SDC(Synopsys Design Constraint) File.
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3. What are the min timing requirements that need to be met.
-- At least, the clock definition is necessary.

-- After clocks have been defined, setup time & hold time of sequentical cells/blocks will be checked.
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4. What if we don't get the required timing ?
-- First, ensure those timing constraints are correct.

-- Then, hold time must be met.

-- If setup time can not be met after using all possible optimization techniques,
maybe only refine the timing constraints (slow down).

Re: What is timing ?

Thank you very much for your time .
I understood most of your comments.

What if the timing is not met by the P&R tool ( I mean after optimization )? How one will fix it ?

Thanks in advance