Resistance measurement from SPEF file

[arp]

Hi,
For calculating the NET RC component,
in spef they are providing the lumped capacitance.
Is there any methods for finding the approx. resistance of the node with out going to another tool!!!
plz help me regarding this..
thanks
arp

 

[dynamicdude]

For extracting the RC values for all nodes, the only way is to use the extractors for modelling them.
RC extraction is one of the most expensive runtime intensive areas of the flow and so sometimes we even get only approximate answers from the tool itself!

For example in a trasistor with 1 million instances, you might have wires maybe upto 5 meters!! and so modelling every piece of interconnect becomes important for Noise/Em/Timing closure. And so approximations might end up in trouble later.

 

[arp]

Thanks Dynamicdude for the quick reply..

Actually I want to calculate the approximate R from the SPEF without going to the tools. for example this is the SPEF definiton of a net

*D_NET *2069 166.454

*CONN
*I *6022:SI I *C 13668.6 13352.2 *D SDFFRHQX1
*I *5720:B I *C 13667.7 12506.9 *D MX2X1
*I *6086:Q O *C 13663.5 13348.9 *D SDFFSX4
*I *5830:A I *C 13638.2 13348.9 *D MX2X1

*RES
1 *2069:285897 *5720:B 140.235
2 *2069:285897 *2069:154377 137.204
3 *2069:154377 *6022:SI 1.97179
4 *2069:154377 *5830:A 19.8711
5 *2069:154377 *6086:Q 2.52875
6 *6086:Q *5830:A 16.7464
*END

In this I want to calculate the delay due to the net between 5830 and 6086.
For measuring the Resistance its showing two resistance paths... one is of 16.74 ohms and other is of 21 ohms... why there is a difference btw these two!!! why there are two paths from 6086 to 5830!!!

 

[utmseng]

Refer to your above question, have you found out how to find the R from the SPEF file? Can you please share if you found it?

I do not see the 21 ohm in the SPEF file you given. Are you referring the 21 ohm as the resistance number given by your delay calculator?

I am using Prime time, and I found that the R calculated by the tool is different from the number given by the SPEF. Any one having any experience on that?

 

[arp]

Hi utmseng

Actually I am writing a script that which finds the values R and C for each net for the same block with different routes.
I just want to get quick check on the percentage change of R&C's by changing the placement.
I am just approximating the net resistance from the spef file.

So in the given spef, to find out the R between 5830 and 6086-- it has two paths then how should i find out from this.... one is directly given as 16 ohms (approx)
other one is through the node 2069.154377 which gives the value approx of 21 ohms..

so can you plz tell me the procedure to get this data from the spef with out going for other delay calculators!!!!!

thanks
arp