TABLE OF CONTENTS Since quantities in an analog model are continuous functions of time, there are an infinite number of quantity values in any given time interval. An analog solver in a VHDL-AMS simulator approximates the quantity values by solving the model equations at a finite number of time steps. The solution at each time step is called an analog solution point. In order to give tool vendors some flexibility, the VHDL-AMS language definition does not specify the details of how the analog solver computes analog solution points. In particular, the definition does not specify the times and frequency with which analog solution points are computed. Simulator vendors may use whatever techniques they consider appropriate to achieve high performance and accuracy.
For some models, however, we may wish to ensure that analog solution points will occur within some time window or with some minimum frequency. We can accomplish this in VHDL-AMS using a step limit specification. The syntax is
step_limit_specification <span class="unicode">?</span> <b class="bold">limit</b> {<i class="emphasis">quantity</i>_name{ , <span class="unicode"> </span> } <b class="bold">others</b> <b class="bold">all</b>): type_mark <b class="bold">with</b> <i class="emphasis">real</i>_expression ;A step limit specification allows us to identify one or more quantities by their names and type, and to specify the maximum interval between analog solution points for those quantities. The step limit specification must appear in the same list of declarations as the quantity declarations to which it refers. The real-valued expression in the step limit specification is the maximum number...
