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estimate clock tree delay

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kinysh

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Hi:

can anyone tell me how to estimate the delay of a clock tree for 500 register.

I have gated clock in my design which have a original clock A.
using dc, I create a clock for that clock B.
but how to set the delay of the clock B relative to clock A.

Or I should set the delay to 0,and I use the clock tree to make sure A and B change at the same phase?

Bests
 

alanray

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I think you should gen clock tree in the backend tool, and then you gen sdf file , then you can check the phycial delay of two clock, and then you
can modify diffenrent clock domain phase, this is call ipo.
 

Nobody

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Just insert some equivalent level of dummy buffer cells . Leave them for backend guys to tune for balance. However you should know it's hard to balance the phase delay in difference clock domain for every corner cases .
 

papertiger

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kinysh said:
Hi:

can anyone tell me how to estimate the delay of a clock tree for 500 register.

I have gated clock in my design which have a original clock A.
using dc, I create a clock for that clock B.
but how to set the delay of the clock B relative to clock A.

Or I should set the delay to 0,and I use the clock tree to make sure A and B change at the same phase?

Bests
Short answer: you don't need to. The backend tool will take care
of the clock, even those gated one.

If you want to have some basic idea of the number,
1->5 driven is used in our case.
5 no buffer.
25 two levels.
125 3 levels.
625 4 levels.

use you real library to get the real number.
(CLKBUFX8 as buffer cell.)
 

papertiger

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kinysh said:
Hi:

can anyone tell me how to estimate the delay of a clock tree for 500 register.

I have gated clock in my design which have a original clock A.
using dc, I create a clock for that clock B.
but how to set the delay of the clock B relative to clock A.

Or I should set the delay to 0,and I use the clock tree to make sure A and B change at the same phase?

Bests
Short answer: you don't need to. The backend tool will take care
of the clock, even those gated one.

If you want to have some basic idea of the number,
1->5 driven is used in our case.
5 no buffer.
25 two levels.
125 3 levels.
625 4 levels.

use you real library to get the real number.
(CLKBUFX8 as buffer cell.)
 

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