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What are the max and min delays in corners?

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medasunil

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Please can any one explain the below

what is min delay in max corner?
what is max delay in min corner?
 

Surfingbull

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fast slow best worst min max

min and max corners refers to extraction corners to account for different PVT.

within the same corner, there is min and max delay (or I prefer to call ealy and late delays). this is to account for OCV.

so you can use a max corner extraction and run STA with OCV at worst-case (late) and better-than-worst-case (early) operating conditions.

for a given maxtime path, the delay on the data path should be late, the delay of capture clock should be early, the delay of the launch clock should be late.

hope that makes sense.
 

    medasunil

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medasunil

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max&min

Thank you for infrmation

I would like to make clear on min & max corners.

Max corner: PVT- Slow Low High
Min corner: PVT-Fast High Low

Now :- Please correct me if iam wrong
Max corner:
setup: PVT- Slow Low High
Hold: PVT- Slow High Low or Fast High Low

Min corner:
setup: PVT- Fast Low High or Slow Low High
Hold: PVT- Fast High Low
 

Surfingbull

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clock early data late setup check

1)
Max corner: PVT- Slow Low High
Min corner: PVT-Fast High Low

Yes. Above correct.

2) I think you only need to check setup in max corner and hold in min corner. I guess if your clock tree is very imbalanced an you worry about clock skew re-distribution in max corner, then you may also need to check hold in max corner. But in that case, you would use the same "slow low high" PVT for hold check because it would still be the worst case.
 

arjun1110

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best worst library sta late early

Hi Sunil,

Your understanding regarding PVT corner is correct.

But when you are doing OCV analysis, consider path between reg to reg, the delay on the data path should be worst delay, the delay of capture clock should be best delay, the delay of the launch clock should be again worst.

The worst delay will get on Max corner and best delay will be on min corner.

This kind of analysis will lead to a too pessimistic results. So what STA tool will does is for given corner it will create two library i.e if you consider max delay corner, it will create worst of worst delay library and worst of best delay library depending upon ocv derate values. Now if consider again the same reg to reg path, the delay on the data path will be worst of worst delay, the delay of capture clock will be best of worst delay, the delay of the launch clock will be worst of worst delay.
 

medasunil

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derate ocv

Thank you Arjun i am clear now.

I am trying to understand weather it is only based in OCV derating or any other factors involved while library characterization.
 

raju3295

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sta delay corners

hi sunil,
OCV, BC_WC are for doing the STA analysis at the chip level, i dont think so these concepts will be used while library characterization,
If am wrong can any correct my words, by saying where these concepts are used while lib char
 

medasunil

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Re: Max & Min delays

Then what about

worst_max.lib
worst_min.lib

worst_max.db
worst_min.db

simillarly
best_max.lib
best_min.lib

best_max.db
best_min.db please can you explain
 

raju3295

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Max & Min delays

lib and db s are diff in format, snps tools use db format so as to have min memory and run time advantages, u can use utility lib2db to convert libs to db format, dbs are binary format.
so in overall there are only 4 libs in ur case
worst_max.lib (=worst_max.db)
worst_min.lib (=worst_min.db ) which corresponds to wrst condition libs
simlary best cond'n libs are two,
 

ydlm42

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Max & Min delays

I am leaning!!!
 

raju3295

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Max & Min delays

sorry ydlm42,,
can you be more clear,,,
 

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