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look up table in verilog-A and spectre support (Read 16361 times)

rajdeep Senior Member Offline Posts: 220 UK	look up table in verilog-A and spectre support Feb 27^th, 2009, 3:28am Hi all, I heard once that Verilog-AMS supports look-up tables. Can it be done in Verilog-A and does Cadence Spectre support this? If yes, can someone post me a small code section how a look-up table can be implemented in verilog-A? Thanks much! Rajdeep
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Geoffrey_Coram

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Re: look up table in verilog-A and spectre support
Reply #1 - Feb 27^th, 2009, 6:41am

$table_model is part of the Verilog-AMS LRM, so it should be supported. Here's an example, copied from the LRM:

Code:

module example_tb(a, b);
  electrical a, b;
  inout a, b;
  analog begin
    I(a, b) <+ $table_model(V(a,b),"sample.dat");
  end
endmodule

and a completely fabricated data file:
Code:

#sample.dat
0 0
1 1
2 4
3 9
4 16

If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: look up table in verilog-A and spectre support Reply #2 - Feb 27^th, 2009, 6:57am spectre has supported this for several years. Regards, Andrew.
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rajdeep Senior Member Offline Posts: 220 UK	Re: look up table in verilog-A and spectre support Reply #3 - Feb 27^th, 2009, 7:31am Thanks a lot Geoffrey! It's working! I could not find this table_model in the Verilog-A LRM, so thought to ask about it straight away in the forum, and as expected got a quick and effective reply. :) Thanks, rajdeep
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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: look up table in verilog-A and spectre support Reply #4 - Feb 27^th, 2009, 8:16am Rajdeep, I assume you must be looking in the wrong LRM? If it's the VerilogA LRM that's shipped with the Cadence tools, then it's in IC5141's VerilogA Reference Manual, and all MMSIM versions. Andrew.
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rajdeep Senior Member Offline Posts: 220 UK	Re: look up table in verilog-A and spectre support Reply #5 - Feb 27^th, 2009, 9:19am Hi Andrew, I downloaded it from web couple of years back and still use that one. It could be that the one that comes with Cadence is a more complete one. thanks for your hint. I will try start using that one from now on..... Rajdeep
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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: look up table in verilog-A and spectre support Reply #6 - Feb 28^th, 2009, 9:59am The Verilog AMS LRM is also on this site - look at the Verilog-AMS link at the top of the page... Regards, Andrew.
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Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: look up table in verilog-A and spectre support Reply #7 - Mar 3^rd, 2009, 6:49am Indeed, $table_model was not in the Verilog-A LRM, nor in Verilog-AMS LRMs until version 2.2. It was donated by Cadence, though, so it was likely in Spectre for a while before that. You ought to get the latest LRM; it's free!
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Dracon Junior Member Offline Posts: 11	Re: look up table in verilog-A and spectre support Reply #8 - Mar 8^th, 2009, 5:44am And what if you want to use $table_model that could change your signal with frequency? I know, you may say that laplace_nd function can be used but is there possibility to create linear changing attenuation?
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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: look up table in verilog-A and spectre support Reply #9 - Mar 8^th, 2009, 8:53am Dracon wrote on Mar 8^th, 2009, 5:44am: but is there possibility to create linear changing attenuation? What do you mean by "linear changing attenuation" ? Attenuation depending on frequency is linear value or dB value ? If it is linear, show me example of dependencies of attenuation.
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Dracon

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Re: look up table in verilog-A and spectre support
Reply #10 - Mar 8^th, 2009, 2:55pm

Yes you are right it is not linear, and this is not what I meant to write. What I want to achieve is to have some kind of impact on attenuation, in modelling cable for example, and express that as 2D look-up table(frequency, attenuation).
As far as I know the $noise_table is very flexible on this aspect but only for noise.

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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: look up table in verilog-A and spectre support Reply #11 - Mar 8^th, 2009, 3:11pm Dracon wrote on Mar 8^th, 2009, 2:55pm: What I want to achieve is to have some kind of impact on attenuation, in modelling cable for example, and express that as 2D look-up table(frequency, attenuation). See http://www.designers-guide.org/Forum/YaBB.pl?num=1227194040
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