Encore SIM EDITOR SOFTWARE User's Guide download pdf (Page 334)

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101

12-8

Event Origin

Debug with Event Origin

For a register variable (reg, integer, time, or real), a value

change always results from the execution of a procedural statement.

For a signal declared as a net data type (wire, tri1, etc.), a value

change usually results from a change in the output of a driving

primitive gate or continuous assign statement (often in a different

scope of the hierarchy from the net declaration itself), or may result

from a procedural force statement.

Since force statements are done outside the logic of the HDL

source code, doing an Event Origin on a force statement may

give misleading results. If line trace information was not saved,

all the drivers of the affected net will be listed but may not be

the cause of the change if the force occurred after the driver was

executed. If line trace information was saved there are two

possible outcomes.

1. A driver was executed at the same time the force was entered.

This case is similar to when line trace data was not saved. The

driver(s) will be displayed but if the force was entered after a driver

executed, that driver would not be the cause of the change.

2. No drivers were executed at the time the force was entered. VirSim

will display the Event Origin.

For a net driven by a single primitive or continuous assign (with the

exception of a procedural force to the net), the event origin is fixed.

For nets and register variables with multiple drivers, the event origin

may change. One or more drivers may be responsible for a particular

net value change, and the set of responsible drivers varies. Since the

drivers may reside in any scope. It can be problematic to establish

the underlying cause of the net value change.

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