Answers Database

Viewlogic Simulation: Forcing a value to a signal and then releasing will cancel any FLOATVAL attributes


Record #110

Product Family:  Software

Product Line:  ViewLogic

Problem Title:
Viewlogic Simulation:  Forcing a value to a signal and then releasing
will cancel any FLOATVAL attributes



Problem Description:



Solution 1:


When simulating a design, if a node that has a FLOATVAL attribute is forced
and then released, the FLOATVAL value will not be restored.  Once released, the
node will go to high impedance.

For example, the global set/reset signal for the XC4000 family of devices known
as GSR has a FLOATVAL=0.  Before asserting GSR, and after simulating for some
amount of time, GSR will take on the FLOATVAL value of '0'.  Once GSR is asserte
d
to '1', if it is released using the 'r' command, it will take on the value of 'Z
'.
Because this value is unacceptable, GSR must be driven Low to de-assert it so th
at
it takes on the value of '0'.





End of Record #110