ModelSim Warning

Kiran

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Jun 5, 2002, 12:17:50 AM6/5/02

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Whenever I use '+' operand in my code, I get the following warning
during simulation

** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand,
the result will be 'X'(es).
# Time: 0 ps Iteration: 1 Instance: /testbench/inst1/instsub1

I always activate the Reset signal in the beginning. Before the reset
has any effect some of the signals are uninitialized and cause the
above warning. How do I get rid of this.

Thanks in advance.

Tom Verbeure

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Jun 5, 2002, 12:27:35 AM6/5/02

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Somewhere hidden in the options or configurations menu of Modelsim, there
is a flag that allows you to disable these warnings...
You can also set this with tcl, see the manual. I would disable the warning
for the first few ns or soo and then enable them again, to avoid masking
real problems...

Tom

k...@semel.fi.spam.wonderful.spam

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Jun 5, 2002, 2:12:02 AM6/5/02

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kira...@msn.com (Kiran) writes:

If the warning comes from the test bench side assign your signals
initial values. It does not matter if your signals are registered or
not you can always assign an initial value. I run into similar
problems with signals that were driven by combinatiorial
logic. Assigning an initial values made warnings go away and did not
affect simulation results because proper values were assigned by logic
rigth after reset. You can do that also with code that you are going
to synthesize but then your synthesis tool is likely to warn you about
that.

Srinivasan Venkataramanan

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Jun 5, 2002, 4:03:41 AM6/5/02

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Hi,
Try the following within VSIM prompt (you could also set this in
modelsim.ini file).

set IgnoreWarning 1

After few ns do

set IgnoreWarning 0

(You could also put the above sequence to a tcl script and load it
automatically every time).

HTH,
Srinivasan

--
Srinivasan Venkataramanan
ASIC Design Engineer
Software & Silicon Systems India Pvt Ltd. - an Intel company
Bangalore, India

I don't speak for Intel
"Tom Verbeure" <tom.ve...@verizon.no.sp.am.net> wrote in message
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Nicolas Matringe

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Jun 5, 2002, 4:18:06 AM6/5/02

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Hi
This is only a warning, you can safely ignore it. It just means that your signal
are not initialized, which is quite normal at 0ps.
You can assign an initial value to your signals (which may cause a synthesis
warning) to get rid of this simulation warning.

--
Nicolas MATRINGE IPricot European Headquarters
Conception electronique 10-12 Avenue de Verdun
Tel +33 1 46 52 53 11 F-92250 LA GARENNE-COLOMBES - FRANCE
Fax +33 1 46 52 53 02 http://www.IPricot.com/

Benjamin Todd

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Jun 5, 2002, 6:07:02 AM6/5/02

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afaics you dont. I always get that warning, its the ones after 0ps you
should worry about

"Kiran" <kira...@msn.com> wrote in message
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Mike Treseler

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Jun 5, 2002, 12:42:36 PM6/5/02

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You can also put your parallel '+' expression inside a process.
The warning is about *adding* 'U's at time 0.

-- Mike Treseler

Jbhasker7

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Jun 13, 2002, 4:36:38 PM6/13/02

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FYI, the message is coming from the "+" overloaded operators defined in the
NUMERIC_STD packages. What is
happening is that during initialization (all
processes execute once), a "+" op
is being performed and at that time, one
of the operands has a metalogical
value.

- bhasker