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Modeling >> Behavioral Models >> (*instrument_module*) usage
https://designers-guide.org/forum/YaBB.pl?num=1424781208

Message started by ranjang on Feb 24^th, 2015, 4:33am

Title: (*instrument_module*) usage
Post by ranjang on Feb 24^th, 2015, 4:33am

Hi All,

I was going through verilog ams periods.vams model and I see at the top (*instrument_module*).

I wanted to know what is the purpose of using this and If I don't keep this what the changes in the result also is it part of verilog ams language.

Thanks,

Title: Re: (*instrument_module*) usage
Post by Ken Kundert on Feb 24^th, 2015, 11:30am

It disables an error message in Spectre that would prevent the model from being used in SpectreRF. SpectreRF cannot handle hidden state if that state affects the behavior of the model. Spectre has a way of examining the model to determine if it contains hidden state, but it is not sophisticated enough to determine if that state affects the behavior of the model. By adding the instrument_module attribute, you are saying any hidden state the model contains is innocuous.

Other that that it in no way affects the behavior of the model, and you can feel free eliminating it if you do not plan to use the model in SpectreRF.

-Ken

Title: Re: (*instrument_module*) usage
Post by ranjang on Feb 25^th, 2015, 4:14am

Thanks Ken for the detailed explanation.

You talked about spectre RF is it different from normal spectre and what for what kind of designs this simulator to be used.

Title: Re: (*instrument_module*) usage
Post by Ken Kundert on Feb 25^th, 2015, 3:49pm

I cannot process that last sentence. Is it a question?

-Ken

Title: Re: (*instrument_module*) usage
Post by ranjang on Feb 25^th, 2015, 9:34pm

Yes this is a question.I wanted to know how the spectre and spectre RF tools different? Also normally we will use spectre or ultrasim solver for normal designs like SMPS,LDOs,ADC,PLL etc but where is this spectre RF simulator used?

Title: Re: (*instrument_module*) usage
Post by Ken Kundert on Feb 26^th, 2015, 2:24pm

SpectreRF is a collection of new analysis that are available in Spectre. They are very powerful and very useful. They were originally targeted for RF circuits but their capabilities are general and they have found wide applicability in analog, mixed-signal and even digital circuits.

Perhaps aspect of the RF analyses of SpectreRF that is the most important is that they extend the small-signal analyses (AC and noise primarily) to periodically driven circuits. All of the circuits you mentioned are periodically driven and so benefit from RF analysis. For example, SpectreRFs' PNoise analysis allows you to predict the noise performance of both the components that make up a PLL (oscillator, pfd/cp, divider, etc.) as well as the PLL itself. As another example, people are now using the Pstability analysis to determine whether switch-mode power supplies are stable. If you browse the Analysis section of this website you will find several application notes that describe how to apply SpectreRF to traditional analog and RF circuits.

-Ken

Title: Re: (*instrument_module*) usage
Post by Geoffrey_Coram on Mar 19^th, 2015, 6:53am

ranjang wrote on Feb 24^th, 2015, 4:33am:

also is it part of verilog ams language.

This is an attribute, which are a sort of magic comment; attributes are part of the language. They are intended to help the simulator work more efficiently, and the language reference manual states that simulators should simply ignore attributes they don't understand (rather than giving an error).