What is CCS and NLDM:
CCS stands for Composit Current Sourse Model, and
NLDM stands for Non-Linear Delay Model. Both CCS & NLDM are delay
models used in timing analyze.
Difference between CCS & NLDM:
- NLDM uses a voltage source for driver modeling
- CCS uses a current source for driver modeling
Why prefer CCS to NLDM:
The issues with NLDM modeling is that, when the
drive resistance RD becomes much less than Znet(network load impedance),
then ideal condition arises i.e Vout=Vin. Which is impossible in
practical conditions.
So with NLDM modeling parameters like the cell delay calculation, skew calculation will be inaccurate.
That is the reason why we prefer CCS to NLDM
In present 22nm technology ccs is using?
ReplyDeleteyes we use these ccs libs only..
DeleteCould you be more specific ?
ReplyDeletewhat you want to know?? please post your full query here.. i will guide you for sure..
Delete@syed yes we use these ccs libs only..
ReplyDeletebro can i have you are mail id?
DeleteIn NLDM delay is calculated based on input slew and output load. According to you ,if output load is equal to its drive strength then it is ideal condition , which is not possible at practical conditions. So we are using ccs library.
ReplyDeletePlease correct me if understood wrongly.
How cell delay is calculated in ccs library ?
bro can i have you are mail id pls?
Deletehow timing is calculated at synthesis stage(rtl to gate level netlist) actually I heard they use wire load models instead of nldm / ccs. But as they are inaccurate now a days we are doing physical aware synthesis . What is it and how is it done
ReplyDelete