How to calculate/interpolate delay values from the Liberty file 3-D lookup table?

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amphibionics

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Anybody knows how to interpolate delay values from the 3-D lookup table in the Liberty file?

here are some sample template:

Code: 
/* 3-D table template f(i_trans, o_cap, r_cap) */
lu_table_template( f_itrans_ocap_rcap ) {
        variable_1 : input_net_transition;
        variable_2 : total_output_net_capacitance;
        variable_3 : related_out_total_output_net_capacitance;
        index_1 (" 0.0000, 1.0000 ");
        index_2 (" 0.0000, 1.0000 ");
        index_3 (" 0.0000, 1.0000 ");
}

/* 3-D table template f(d_trans, c_trans, r_cap) */
lu_table_template( f_dtrans_ctrans_rcap ) {
        variable_1 : constrained_pin_transition;
        variable_2 : related_pin_transition;
        variable_3 : related_out_total_output_net_capacitance;
        index_1 (" 0.0000, 1.0000 ");
        index_2 (" 0.0000, 1.0000 ");
        index_3 (" 0.0000, 1.0000 ");
}

Thank you.;-)
 
Last edited by a moderator:

Loopup table here is a reference, depend on your logic, each net/pin/port will have fixed load and fan-out , depend on that load and fan-put , pin transition and output capacitance will calculated and based on that value, same positional value will be taken in timing analysis.
 

Thanks Rahul.
Unfortunately, I already know the basic of characterization with Liberty files which you are mentioning above.
What I really do want is the mathematical interpolation expression for 3-D lookup table.
Ex.
D0 = (tr20*c20)*D11 + (tr20*c01)*D12 + (tr01*c20)*D21 + (tr01*c01)*D22

where D0 is the interpolated delay value from a 2-D table.

I believe that interpolation methodology is a proprietary thing.
I hope somebody could share.

Thanks.
 

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