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Liberate_AMS for .lib generation.

Hi,

I'm having Liberate_AMS for characterization of AMS blocks. Can I use the same for the characterization of a std cell library ?

The main difficulty involved is in generating the input stimulus files which need to be given in the form of tables in Liberate_AMS whereas it can be included with the attribute -vector inside the template file (in case of Liberate).

Still I managed to manually create those table files for ** number of cells. After that I included those tables using the define_table command in the template file. I had to give ** define table commands (1 for each cell) . But I'm getting an error regarding "delay_template" not defined.

After all , I wanted to know, if characterising multiple cells (by including multiple input stimulus files) is possible in Liberate_AMS ? Or is it a futile attempt trying to do that ?

Is there an inherent limitation on the number of cells that can be characterized using Liberate_AMS in a single run ? (other than the brute force way of characterising 1 cell at a time and merging all of them- as I have huge number of cells - typically the number of cells usually present in a std cell library).

Guangjun Cao over 7 years ago

Liberate_AMS does one cell characterisation in each run. It is for AMS/Analog block or large IO block characterisation.

For standard cell characterisation, Liberate is the right choice, which can automatically generate all valid arcs after pre-characterisation analysis by the tool using InsideView technology.
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anandmohan over 7 years ago

Hi,

I'm using Liberate_AMS for characterising an AMS block....Even though my desired arc is getting characterised, the log file is getting filled with the error message attached below:

I'm attaching the screenshot of the same.

I'm not aware of what this feature 'Spectre_char_opt' is all about. Where am I inadvertently invoking it ?

Guys, any help wud b great....
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Guangjun Cao over 7 years ago in reply to anandmohan

Liberate has this variable, spectre_use_char_opt_license, which is a common setting for all Liberate tools. By default it is "1", ie. "on". You can use set_var spectre_use_char_opt_license 0 to turn this off, if you do not have the required license for char_opt feature.
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anandmohan over 7 years ago in reply to Guangjun Cao

Thanks Guangjun....Could you let me know what is the functionality of this feature ?
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Guangjun Cao over 7 years ago in reply to anandmohan

Hi Anand,

Below is what's said in the Liberate manual,

---------

This parameter enables Liberate to checkout
Spectre_char_opt licenses upfront instead of MMSIM
licenses, which are only checked out by Spectre. This will
minimize the overhead associated with checking out of Spectre
licenses.

--------

It is a basically a different license package that offers better integration of Cadence characterization/simulation tools.

I hope this helps.

Guangjun
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anandmohan over 7 years ago in reply to Guangjun Cao

Thanks Guangjun...
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anandmohan over 7 years ago in reply to anandmohan

Hi,

I'm confused on the attributes setup_rising, hold_rising, setup_falling, hold_falling....apart from that I see rise_constraint, fall_constraint within each of those attributes. Whats the meaning of each of those attributes. Not getting a clear cut understanding from the user manual....

I'm having a clk signal with the active edge as the rising edge.
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Guangjun Cao over 7 years ago in reply to anandmohan

setup/hold_rise/falling are time_attribute value, which describes timing constraint between pin and related_pin when the signal at related_pin rises/falls (this depends on effective edge or level of clock). Depending on the data value, the output signal may rise or fall, hence the rise/fall_constraint section. All these are defined/explained in Liberty syntax manual. They are not Liberate-specific, therefore, not necessarily documented in Liberate manual.
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anandmohan over 7 years ago in reply to Guangjun Cao

Ok..So if I've understood correctly, if my active clk edge is rising edge, only setup_rising and hold_rising are valid attributes right ?........
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Guangjun Cao over 7 years ago in reply to anandmohan

yes.
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