B. The Stepping Module of Minimos-NT

Stepping is a fundamental infrastructure feature of any simulation tool, since it is important for both usability and performance considerations. For example during steady-state analysis several operating points are normally of interest to extract an I-V curve. On the one hand side the user can specify these points by variables in one input-deck rather than starting the simulator again and again. On the other hand side the solution of one operating point is normally a very good initial guess for the next one, resulting in a significant speed-up of the complete simulation.

This application of stepping variables is well-known and for reasons of consistency the definition of the time or frequency domain has been based on these concepts. This allows to employ the various powerful stepping functions also for transient and small-signal analysis.

Stepping is controlled via the step function family. The main purpose of the step functions is to introduce parameters for the simulation. There are several step functions available:

Table B.1: Stepping functions provided by MINIMOS-NT.

Function	Functional Parameters
step	start and stop value, delta, log, deltaMin, deltaMax
stepN	start and stop value, number of steps, log, deltaMin, deltaMax
stepTbl	table of values
stepCrv	curvefile, parameter, response, state
stepSingle	single value
stepCond	lower boundary, upper boundary, formula, error, maxCount

Common to all different types of stepping functions are the administration parameters name, pri, slot, prev, and post:

• pri denotes the priority of the parameter. For each combination of values of the stepped parameters a single simulation is run. The parameter with the highest priority runs fastest. Default priority is -1. Overruling of the priority of time and frequency is prohibited, because these variables always get the highest priority during stepping initialization. Furthermore, it is not allowed to combine their stepping functions with other input-deck functions.

• For consecutive stepping of different parameters, the optional arguments slot, prev, and post can be used. Only parameters with the same value of slot are stepped together, while other parameters are given the value defined in prev or post, depending on whether the current slot comes before or after the value given in slot. Parameters without a value in slot are stepped in slot -1 as default. If prev and post are not specified, the first or last value of the stepping parameter is used, depending on the slot position.

Stepping control (see Appendix B.4) adjusts the standard delta within a range specified by deltaMin and deltaMax. If these optional arguments are not given, both variables are set to delta. In the case of user specified values they should fulfill deltaMin $<$ delta $<$ deltaMax. But this is not enforced by the simulator.