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Nexxim Simulator >
Nexxim Transient Analysis >
Running Transient Analysis from the Netlist Editor >
Transient Analysis Netlist Syntax

Transient Analysis Netlist Syntax

To execute transient analysis simulation on a circuit, add a .TRAN statement to the netlist. The syntax for the basic .TRAN statement is:

.TRAN step stoptime

All transient analyses start at time 0. The step argument is a suggested initial step size and also influences the maximum step size that will be used. The stoptime argument sets the end of the transient solution interval. For example, to execute a transient analysis on an interval from time zero to one microsecond with a suggested initial step size of one nanosecond:

.TRAN 1e-9 1e-6

Transient Analysis Accuracy Syntax

Two arguments on the Transient Analysis statement provide broad control over the tradeoff between speed and accuracy:

The ERRPRESET argument overrides the settings for several options that control the tradeoff between speed and accuracy.

**Errpreset Controls**
Option	errpreset
Option	None	relaxed	moderate	strict
reltol	x1	x10	x1	/10
trtol	7	7	7	10
relref	allloc	sigglob	sigglob	allloc
method	trap	trap	trap	ndf2
maxstep	stoptime/100	stoptime/12	stoptime/50	stoptime/100
update_jacobian_period	3	3	3	1

The RELREF argument controls how the norms are computed for the delta check, function check, and LTE checks. Point-local means the norm is local to the signal and to the time step. Local means the norm is local to the signal but considers the maximums over all time-steps. Global means the norm is global for the entire circuit over all time-steps. The settings for relref are:

• pointlocal = Point-local for delta, function, and LTE

• alllocal = Local for delta, function, and LTE

• sigglobal = Local for function, global for delta & LTE

• allglobal = Global for delta, function, and LTE

Transient Analysis Noise Syntax

To enable transient noise analysis, the .TRAN statement takes additional arguments.

.TRAN step stoptime
+ NOISEFMAX=val
+ NOISESCALE=val
+ NOISESEED=val
+ NOISEFMIN=val

**Transient Noise Arguments**
Argument	Description	Unit	Default
NOISEFMAX	The highest frequency to analyze for pseudorandom noise. Must be non-zero to enable transient noise analysis. Maximum transient timestep will be set to 1/NOISEFMAX.	Hz	0
NOISESCALE	Scale factor	None	1
NOISESEED	Random number seed. Using the same seed generates the same set of random values	None	None
NOISEFMIN	Lowest frequency to analyze for noise. Below NOISEFMIN, noise power density is constant. 1/NOISEFMIN must be less than the transient analysis stoptime.	Hz	NOISEFMAX
NOISESTART	Noise start time	Second	0

Transient Analysis File Arguments

Arguments are available to read and write initial and final state information from files.

.TRAN step stoptime
+ READ_STATE=file_reference
+ WRITE_FINAL_STATE=file_reference
+ WRITE_INITIAL_STATE=file_reference

READ_STATE reads the initial values of node voltages from the specified file.

WRITE_FINAL_STATE writes the final values of node voltages to the sepcified file.

WRITE_INITIAL_STATE writes the initial values of node voltages to the sepcified file.

See File References for details on references to external files.

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