Answers Database

NGD2EDIF M1.3: WARNING:basnu - This design contains the undriven net "<net name>"


Record #2244

Product Family:  Software

Product Line:  Merged Core

Problem Title:
NGD2EDIF M1.3: WARNING:basnu - This design contains the undriven net
"<net name>"



Problem Description:
Keywords: NGD2EDIF, GSR, GTS, GLOBALSETRESET, GLOBALTHREESTATE,
undriven

Urgency: Hot

General Description:

NGD2EDIF may report the following warning:

WARNING:basnu - NOTE: This design contains the undriven net "GSR" which you must
 drive during simulation to get valid results.

This warning may apply to any of the following signal names:

   GSR
   GTS
   GLOBALSETRESET    (Mentor Graphics)
   GLOBALTHREESTATE  (Mentor Graphics)


Solution 1:

Even though you may not be using the global set/reset or global
three-state signal in your implemented design, these signals still
exist in the timing simulation model that NGD2EDIF writes.  To
initialize simulation correctly, these nets should be driven at the
start of simulation as follows:

GSR/GLOBALSETRESET:    Asynchronous set/reset of all flip-flops
		       Logic 1 at time 0
		       Logic 0 after time Tmrw*

GTS/GLOBALTHREESTATE:  Three-state control of all user outputs
		       Logic 0 at time 0

*Tmrw: Minimum master-reset pulse width as given in the Programmable
Logic Data Book under CLB Siwtching Characteristic Guidelines.



End of Record #2244