Answers Database

Viewsim: About ? Nodes in Timing Simulations


Record #101

Product Family:  Software

Product Line:  ViewLogic

Problem Title:
Viewsim: About ? Nodes in Timing Simulations


Problem Description:
Here is a list of solutions to resolve "?" during timing simulation.

Keep in mind that "?" are not fatal; the simulation will be correct for
values that are displayed.


Solution 1:

XSIMMAKE was not used. You should use XSIMMAKE functional flow to prepare
a design that contains XBLOX, Xabel, or MEMGEN components for simulation.



Solution 2:

XSIMMAKE was used, but XNFBA failed to completely back-annotate the design.
This can happen if you use the CLB or IOB symbols in XC3000 designs.



Solution 3:

Invert Sense in ViewDraw is being used.  Invert Sense in Viewdraw attaches
a "~" to the front of the netname.  This is not a valid xnf netlist symbol,
so WIR2XNF changes it to a "-". The net names no longer match, and the
question marks appear.	There are two solutions to this problem.  The first
solution is to avoid using the Change Sense feature in Viewdraw. The second
solution is to run XNF2WIR with the <design>.crs file.	The .crs file has
the net name translations from WIR2XNF. Use the following syntax:
	
xnf2wir	-x -c filename.crs filename.xnf	



Solution 4:

Global nets are being used with any version of ViewDraw prior to version 5.
This includes 4.1.2 and 4.1.3.	Powerview, PROseries and Workview Office fix
this.  The problem is with the annotator in ViewDraw. When it annotates the
values back to schematic, if the global net is on the top level, it will be
able to find it.  If it is in a lower level (under a symbol) it won't find
the net.



Solution 5:

Using /'s or \'s in netnames. Don't use these characters in names. This
causes a problem with the translation tools, as these characters are used
to indicate hierarchy.



Solution 6:

Design is an CPLD design.  Currently, there is no back-annotation tool for
CPLD schematic designs.  Most internal nets will be marked "?". CPLD
designs tend to undergo alot of collapsing during the fitting process and
many of the original nets no longer exist.



Solution 7:

One final possible cause is adding the attribute "LABEL" to the macro.
This is not the same as using "ADD->Object Label" from PROcapture, for
example, which does not cause problems.

Strip your macro of the attribute "LABEL=xxxx", if it has been specified.



End of Record #101