You can use the report_drivers
Tcl command to
determine what signal is driving a value on an HDL
object. The syntax is as follows:
report_drivers <hdl_object>
The command prints drivers (HDL statements doing the assignment) to the Tcl Console along with current driving values on the right side of the assignment to a wire or signal-type HDL object.
You can also call the report_drivers
command from
the Object or Wave window context menu or text editor. To open the context menu (shown in the
following figure), right-click any signal and click Report
Drivers. The result appears in the Tcl console.
Figure 1. Context Menu with Report Drivers Command Option