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Virtuoso AMS Environment User Guide

Variables for ams.env Files

scmethod

Specifies the integration method to use.

Syntax

amsDirect.simcntl scmethod cyclic "traponly" | "gear2" | "euler" | "trap" | "gear2only" | "trapgear2"

Values

 

traponly

Uses almost exclusively the trapezoidal rule method.

gear2

Uses the backward-Euler and second-order Gear method.

euler

Uses exclusively the backward-Euler method.

trap

Uses the backward-Euler and the trapezoidal rule methods.

gear2only

Uses almost exclusively Gear’s second-order

 

backward-difference method.

trapgear2

Allows all three integration methods to be used.

Description

This variable determines the value assigned to the tran method option in a generated simulation control file.

Example

You set the variable

amsDirect.simcntl

scmethod

cyclic "traponly"

In response, the generated simulation control file contains

amsAnalysis tran

+stop = 0.001

+method = traponly

April 2004

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Product Version 5.3

Virtuoso AMS Environment User Guide

Variables for ams.env Files

scmodelevaltype

Specifies whether standard SPICE-like equations or table (accelerated) models are used to evaluate bsim3v3 and bsim4 models.

Syntax

amsDirect.simcntl scmodelevaltype cyclic "s" | "a"

Values

 

s

Instructs the simulator not to use table models for any instances.

 

This is the default.

a

Instructs the simulator to use table (accelerated) models

 

whenever possible. This global option applies to the entire

 

simulated design. You can override this instruction on specific

 

model cards by setting mos_method = s as an option on those

 

cards.

Description

This variable determines the value assigned to the mos_method option of the options statement in a generated analog simulation control file. AMS Designer writes the mos_method option to the analog simulation control file only when thescusemodeleval variable is set to t. For additional information, see “scusemodeleval” on page 543.

Example

You set the variables

amsDirect.simcntl

scusemodeleval

boolean

t

amsDirect.simcntl

scmodelvaltype

cyclic

"a"

In response, the generated analog simulation control file contains

amsOptions options + mos_method = a

April 2004

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Product Version 5.3

Virtuoso AMS Environment User Guide

Variables for ams.env Files

scmosvres

Specifies the voltage increment for the mosfet table model interpolation grid. Smaller values reduce the interpolation error, but might increase memory consumption. A value of 20mV is appropriate for analog circuits that are extremely sensitive to small model parameter variations, and subthreshold and substrate currents.

Syntax

amsDirect.simcntl scmosvres string "vresolution"

Values

vresolution

The default value is 0.50.

Example

amsDirect.simcntl scmosvres string "0.02"

Sets the interpolation grid value to 20mV.

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Virtuoso AMS Environment User Guide

Variables for ams.env Files

scnarrate

Narrates the simulation.

Syntax

amsDirect.simcntl scnarrate boolean t | nil

Values

 

t

The simulator narrates the simulation. This is the default.

nil

The simulator does not narrate the simulation.

Description

This variable determines the value assigned to the options narrate option in a generated simulation control file.

Example

You set the variable

amsDirect.simcntl

scnarrate

boolean nil

In response, the generated simulation control file contains

amsOptions options + narrate = no

April 2004

507

Product Version 5.3

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