Simulator Configuration Guide for Synopsys Models

Simulator Configuration GuidevChapter 5: Using NC-Verilog with Synopsys Models$lm_unknowns Command ReferenceThe $lm_unknowns command lets you override the hardware modeler’s defaulthandling of unknown values for specified instances or pins, or for all hardware modelinstances in the simulation.Syntax$lm_unknowns (“option=value” [,”option=value”,...] [, “device_or_pin”])ArgumentsYou can use the following values for “option=value”:propagate=yes | noWhen “yes” (the default), enables the “on_unknownpropagate” statement, if there is one, in the model’s optionsfile (for example, TILS299.OPT) for the specified instance orpin, or for all hardware model instances in the simulation. Setpropagate=no if you want to disable or override the“on_unknown propagate” statement in the .OPT file for aspecific instance or pin.NoteIf there is no “on_unknown propagate” statement in the model’s .OPT file,unknown propagation is disabled even if you use” $lm_unknownspropagate=yes”. For the “propagate=yes” option to have an effect, theremust be an “on_unknown propagate” statement in the model’s .OPT file. Formore information about the on_unknown statement, refer to the ShellSoftware Reference Manual.value=previous | high | low | floatSpecifies the value to be passed to the device when anunknown value is passed to the modeler. The default is“previous”, meaning that if the simulator sets an input pin to“unknown”, the modeler drives the input to its previous value.For more information, refer to the description of set_previousin the on_unknown reference pages in the Shell SoftwareReference Manual.sequence_count=num_sequencesSpecifies the number of random sequences to propagateunknowns through the hardware model. The num_sequencessetting is an integer of value 0 (the default) through 20. TheOctober 6, 2003 Synopsys, Inc. 103