Regarding Prime time Static Timing analysis

Hi people,

I found the following lines of code in the timing library file which is input to the Prime time



Can someone help me as to what the look up table is about as I am very confused with the variable 1,2 and the index_1 and 2 value


Regards
Arvindh.S

a liberty file provide the timing (also area, power...) of internal path of a cell/macro.
for example the timing to go from a input A to output Q of a buffer is function of the input transition on seen on pin A, and the output load seen by the pin Q, then the tools based on the trans/load, used the lock-up table to know the propagation delay, rise/fall time...

in your case, the value provided could be for info, you need to check in the file where "delay_template_6x6" is used which values are given for index_1 and index_2, sometime there are similar, sometime completely different.

as well, the max value in the index_1 is normaly the max_transition, and similarly the max value of the index_2 is the max_capacitance, to indicate to the designer, that the timing is out the lock-up table, and the extrapolation could be (or is) erronous.

Hi
Thank you for the reply. But I couldn't understand what you meant by capacitance value in index 2.
The max transition in index 1 is because of the capacitance value right?

Arvindh19 said:

Hi people,

I found the following lines of code in the timing library file which is input to the Prime time

Code:

lu_table_template(delay_template_6x6) {
    variable_1 : input_net_transition;
    variable_2 : total_output_net_capacitance;
    index_1 ("1000.0, 1001.0, 1002.0, 1003.0, 1004.0, 1005.0");
    index_2 ("1000.0, 1001.0, 1002.0, 1003.0, 1004.0, 1005.0");

Can someone help me as to what the look up table is about as I am very confused with the variable 1,2 and the index_1 and 2 value


Regards
Arvindh.S

Click to expand...

Hi Arvindh ,

The index_1 represents the value for variable_1 ie input_net_transition
Similar;y , index_2 represents output cap.

These values are derived using experiments and load spec .

By using this combination you will calculate the delays.
Eg : for 1000 input net tranistion and 1000 cap what is the delay?

You will have 6 X 6 matrix representing the delay values for these combination of slew and load