Section 14.2

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The SystemVerilog language is defined in terms of a discrete event execution model. The discrete event simulation is described in more detail in this section to provide a context to describe the meaning and valid interpretation of SystemVerilog constructs. These resulting definitions provide the standard SystemVerilog reference algorithm for simulation, which all compliant simulators shall implement. Note , though, that there is a great deal of choice in the definitions that follow, and differences in some details of execution are to be expected between different simulators. In addition, SystemVerilog simulators are free to use different algorithms than those described in this section, provided the user-visible effect is consistent with the reference algorithm.

Section 14.3

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The pre-active region is specifically for a PLI callback control point that allows for user code to read and write values and create events before events in the active region are evaluated (see section 14.4 PLI callback control points, below).

Section 14.4

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There are two kinds of PLI callbacks, those that are executed immediately whenever some specific activity occurs when some object changes value in an update event, and those that are explicitly registered as a one-shot evaluation event.

Remove editor’s note:

Editor’s Note: The preceding paragraph does not account for all types of callbacks. For example: cbStmt, cbEnterInteractive, cbStartOfReset, etc. These and some other callbacks are not logic value related, and they may occur more than one time after being registered.