Liberty files: [Input Pin] Capacitance, Rise/Fall Capacitance Ranges Attributes
Hi all,
I'm was trying to understand all aspects of the liberty file and I came across some questions.
I'm looking at the input/inout pin attributes - capacitance, rise/fall capacitance, rise/fall capacitance range and would like to know more about them. From what I understand, I know that the pin capacitance attribute is the measured capacitance that is measured directly in SPICE calculations and the rise/fall capacitance values/ranges are calculated based on the pin capacitance value for rising and falling waveforms.
I assume that the pin capacitance value is measured at the high/low levels of the signal whereas the rise/fall capacitance values are related to their respective edges, correct?
As a rule of thumb, do the capacitance and rise/fall capacitance values have to be within the rise/fall capacitance ranges? It makes sense that the rise/fall capacitance value has to be within the rise/fall capacitance ranges but what if I come across a (just) capacitance value that is outside of the rise/fall capacitance ranges?
Thanks in advance!