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:
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 figure below), right-click any signal and click Report Drivers. The result appears in the Tcl console.