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Simulation Problem

 
 
Naimesh
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      06-29-2004
I am using XILINX ISE 6.1 and Modelsim for simulation. when I run the
simulation I get follwoing warning.

Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand, the
result will be 'X'(es).
# Time: 0 ps Iteration: 0 Instance: /testbenchcmedmain/uut/dpll1
# ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic
operand, the result will be 'X'(es).
# Time: 0 ps Iteration: 0 Instance: /testbenchcmedmain/uut/dpll1

Now when I see the WAVE window I dont get any X'es in any signal. How
do I find out which signal is creating the problem.

Thanks for any help.

Naimesh
 
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Tim Hubberstey
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      06-29-2004
Naimesh wrote:

> I am using XILINX ISE 6.1 and Modelsim for simulation. when I run the
> simulation I get follwoing warning.
>
> Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand, the
> result will be 'X'(es).
> # Time: 0 ps Iteration: 0 Instance: /testbenchcmedmain/uut/dpll1
> # ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic
> operand, the result will be 'X'(es).
> # Time: 0 ps Iteration: 0 Instance: /testbenchcmedmain/uut/dpll1
>
> Now when I see the WAVE window I dont get any X'es in any signal. How
> do I find out which signal is creating the problem.


It's not a problem. Note that they are warnings and occur at time = 0.
This is typically the result of doing an integer conversion (either
directly or implicitly) on an std_logic_vector or unsigned/signed in
combinational logic.

e.g. n:1 mux
out <= input_vector(to_integer(unsigned(select_vector));

These vectors are 'X' at time=0, hence the warnings. It is possible to
disable them but unless there are a huge number of them, I usually just
ignore them.
--
Tim Hubberstey, P.Eng. . . . . . Hardware/Software Consulting Engineer
Marmot Engineering . . . . . . . VHDL, ASICs, FPGAs, embedded systems
Vancouver, BC, Canada . . . . . . . . . . . http://www.marmot-eng.com

 
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ALuPin
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      06-29-2004
http://www.velocityreviews.com/forums/(E-Mail Removed) (Naimesh) wrote in message news:<(E-Mail Removed). com>...
> I am using XILINX ISE 6.1 and Modelsim for simulation. when I run the
> simulation I get follwoing warning.
>
> Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand, the
> result will be 'X'(es).
> # Time: 0 ps Iteration: 0 Instance: /testbenchcmedmain/uut/dpll1
> # ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic
> operand, the result will be 'X'(es).
> # Time: 0 ps Iteration: 0 Instance: /testbenchcmedmain/uut/dpll1
>
> Now when I see the WAVE window I dont get any X'es in any signal. How
> do I find out which signal is creating the problem.
>
> Thanks for any help.
>
> Naimesh



Are you sure that you displayed all signals?

Are your registered signals resetted so that they start up in a defined
state?
 
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Naimesh
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      06-30-2004
(E-Mail Removed) (ALuPin) wrote in message news:<(E-Mail Removed). com>...

I think I displayed all the signals and all are reseted with the RESET signal.

The entity in which I m getting error i.e. Instance: /testbenchcmedmain/uut/dpll1


does have a integer conversion from std_logic_vector. How do I remove it.


> Are you sure that you displayed all signals?
>
> Are your registered signals resetted so that they start up in a defined
> state?

 
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