The RC network is incomplete for net

[stevenv07]

Hello Everyone,

I have a problem when extracting the timing report (after postRoute). The Cadence Innovus tool shows some warnings as follows:

*WARN: (IMPESI-3014): The RC network is incomplete for net ... As a result, a lumped model will be used during the delay calculation which may compromise the timing accuracy. To resolve this, check parasitics for completeness, re-extraction may be required.

Could you help me explain this issue?

Thanks so much.
Steve.

 

[BradtheRad]

Should we surmise incomplete for net means that you need to alter wiring or components in your netlist? Is the capacitor connected directly across supply rails? It may help to install a resistor inline with the capacitor. Then the simulator can calculate a usable RC time constant.

Or change your capacitor to a model that contains some amount of ESR.

Your error message suggests the simulator is unhappy with your model. So it reports that it shall substitute a different model.

 

[ThisIsNotSam]

Should we surmise incomplete for net means that you need to alter wiring or components in your netlist? Is the capacitor connected directly across supply rails? It may help to install a resistor inline with the capacitor. Then the simulator can calculate a usable RC time constant.

Or change your capacitor to a model that contains some amount of ESR.

Your error message suggests the simulator is unhappy with your model. So it reports that it shall substitute a different model.

I don't think this is it. I have seen this error message when there were problems during routing, but still you asked the tool to do extraction.

In most cases, these were benign. In other cases, it actually represented an open somewhere which the tool did not know how to address. for some reasons it happened a lot with the nets that are routed from the IO cells to the core, as if there was some issue figuring out their connectivity.

And let's not forget this is a warning. Not necessarily something that will kill your chip.