eldo_user

Setting Up An Analysis
Saving and Restarting Transient Simulations
• Skip DC operating calculation
• Skip a portion of transient simulation in subsequent run of the same design
Save/restart can also be used to backup data for long simulations, thus avoid re-simulating
design from the beginning if a power outage occurs.
There are two ways to save simulation information:
• .SAVE command saves analysis data to a file at DC, transient or end of transient
• .OPTION SAVETIME=val saves results every val CPU hours
There are three ways to read previously saved results:
• .USE command
This reads the saved DC result, and can be used as nodeset, ic, guess values.
Used to load DC or operating point information for one or more parts of the circuit to be
simulated; its application is thus in cases where a large or complex circuit is to be
simulated, and the DC or operating point data for parts of the circuit is already known.
Multiple .USE commands may be used in a simulation.
• .LOAD command
This reads the saved DC result, and can be used as nodeset, ic, guess values. Works in a
similar way to the .USE.
• .RESTART command
This reads transient and end of transient saved result. It only supports simple TRAN
simulation. .TRAN associated with .STEP, .MC, .WCASE, .NOISETRAN are not
supported. Modification of circuit topology is not allowed. Old and new waveforms are
concatenated.
The .RESTART command is different from the .USE command in several ways. Firstly,
whereas the .USE information may apply only to part of the circuit, .RESTART data
always applies to the whole circuit. In fact, the .RESTART command first checks that
the node names specified in the file used to restart the circuit, exactly correspond to
those specified in the circuit description file where the .RESTART command is placed.
The .RESTART command may be used to either load the operating (DC) point data and
thereafter perform a transient simulation, or it may be used to restart a transient
simulation from a specific point where the simulation had been interrupted in an earlier
run. To carry out a transient analysis from a specific point, the .TRAN command
parameters need to be changed to specify the new simulation times.
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Eldo® User's Manual, 15.3