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AR# 994

Foundation: Improper Netlist error while loading functional simulation

Description

This problem mainly occurs with Foundation 6.0.0, but may
also occur with 6.0.1.

While executing a functional simulation on a schematic
design, the tools report that you have an improper netlist
for gate array.

This error may be issued because the XNF file(s) generated by
XABEL and/or XVHDL have EQN symbols in them. These EQN
symbols are not simulatable and the tools issue the netlist
error.

Another cause of the error is using the "FPGA symbol" option
when creating macro symbols. This option should only be used
for board-level simulation.

Solution

1

During XABEL and VHDL synthesis, the IMPROVEX program creates
files named <module_name>.XNF and <module_name>.XAS. The XAS
file is functionally equivalent to the XNF file, but does not
contain EQN symbols.

Before performing functional simulation, make a backup copy
of the XNF file, renaming it to <module_name>.XN2. Then
rename the XAS file to XNF and then run functional
simulation.

After functional simulation, rename the XN2 file back to XNF
for the implementation and timing simulation steps.

2

One other cause of this problem can be if a symbol on the
schematic is set to type "FPGA Symbol". To check this, select
the symbol in the schematic editor and type Ctrl-E. This
will bring up the Symbol Editor. In the upper right hand
corner is a checkbox labeled "FPGA symbol". Uncheck this box
and try the simulation again.

3

For VHDL modules you can choose not to run IMPROVEX (uncheck
the IMPROVEX box in Synthesis->Options). This will produce
an XNF file without EQN symbols. If you do not run IMPROVEX
before functional simulation, before the translation step it
is strongly recommended that you recompile the VHDL module(s)
and run IMPROVEX.
AR# 994
Date Created 05/08/1996
Last Updated 01/02/2000
Status Archive
Type General Article