Dear All,
I saw the Cadence-post (please see at the end of this post) titled:- What is difference between "node" and "nodetoground" captab output, and how to access captab results.
It says that one can use the OCEAN command 'pv' to find the node-to-node and node-to-ground capacitance.
I ran a dcOP analysis and then I opened the calculator. I typed pv("/I0/ref_core/in: vssa" "Fixed" ?result "captab"). /I0/ref_core/in and vssa are two nodes in the schematic.
But, it did NOT show any value in the calculator. Perhaps I am missing something.
Could anybody please tell how to use the OCEAN command 'pv' either in calculator or in OCEAN script to find the captab results.
Kind Regards,
What is difference between "node" and "nodetoground" captab output, and how to access captab results
Problem
You are using the captab option with dc or transient analysis in spectre. This gives a table of node capacitance for the circuit. You can choose either "node", "nodetoground" or "nodetonode" detail options for this table.
"spectre -h info" gives following:
***
9 detail=node
How detailed should the capacitance table be?
Possible values are node, nodetoground or nodetonode.
***
What is the difference between the "node" and "nodetoground" ?
How to access capacitance values from captab results?
Solution
The "node" capacitance is the total node capacitance, which is the sum of node to ground (reference to ground) capacitance, and node to other nodes (reference to other nodes) capacitance.
So, if I have this topology
c1 (NODE 0) 5pf
c2 (NODE a) 1pf
c3 (NODE b) 2pf
and there are no other capacitances, then
"node" capacitance for NODE is
5pf + 1pf + 2pf = 8pf.
"nodetogroud" capacitance for NODE is
5pf
"nodetonode" will list out c2 and c3 values of 1pf and 2pf.
The spectre netlist will contain something like:
captabInfo info what=captab detail=node where=rawfile
You can then use in ADE -> Results->Print Capacitance Table to access the captab results. You can also access the results in the Results Browser and calculator.
To access results in Results Browser, open psf/raw directory and check results created in folder like captab-info.captab.
To access results in calculator, you can use ocean ‘pv’ function something as mentioned below:
pv("NODE: NODE" "Total" ?result "captab")
or
pv("NODE: NODE" "Variable" ?result "captab")
or
pv("NODE: NODE" "Fixed" ?result "captab")