Local Skew & Global Skew

[kumar_eee]

global skew

What is local skew & global skew?

 

[handsome]

local skew

locak skew: skew between the launch reg's clock and the capture reg's clock

global skew: the max skew in the clock tree

If any error,please correct me

 

[kapil_vlsi1]

local skew global skew

Local Skew : Source and Destination flop insertion delay is called local skew.

Global Skew : Max insertion delay minus Min Insertion Delay is called Global Skew.

 

[arjun1110]

local skew and global skew

Hi Kapil,

What is the significance of Global skew.

Regards,

 

[kapil_vlsi1]

what is global skew

Significance of Global Skew is it finds out the delay of the clock tree in such a way that it removes the setup violation as well as Hold violation. In this context, we have to use skew balancing to get the required slack.

Hope this helps...

 

[arjun1110]

why global skew?

Hi Kapali,

>>Significance of Global Skew is it finds out the delay of the clock tree in such a way that it removes the setup violation as well as Hold violation.

I am not clear with above statement? How global skew removes the setup and hold violation. Please will elobarate.

Regards

 

[raju3295]

skew balancing

good point to discuss, generally even a cts algoritham quality is estimated on the basis of the global skew, but i dont get why it is of importance, if a local skew b'wen adjusant registers is small that will help in timing

 

[zhipeng]

No idea why global skew is of any importance at all...

Local skew should be generally minimized, or sometimes could be increased for a too slow path between two registers. And skew between registers driving synchronous output should be generally minimized? Is that correct? Is there any situation where global skew matters at all?

 

[rca]

the EDA speaks also of the useful/local/global skews
useful is as you call the local skew
the local skew is the skew in a sub-group
global skew is the skew that include all clocks pins.

 

[wkong_zhu]

How to report local skew?
It seems that Primetime can only report global skew.

 

[rca]

that's right, PrimeTime can not repot local/skew skew.
But the most important is the setup/hold.... checks passed.

the skew/clock reports some info on the clock tree quality, that's all.

 

[semi_jl]

In my opinion, if you are working on a chip (flat design), the global skew is not important if you can close timing, especially for hold.
Buf if you are working on a block and it is a full chip clock domain, the global skew will make effect at full chip timing for global clock balance. You need to meet the latency &. skew requirements for chip timing close.