ModelSim question

Not exactly a VHDL question but hope someone knows the answer.

When running a simulation earlier today and looking at the wave window of
ModelSim I got the following reading when I tried to read the value of an
integer variable: ?(23) ... ?(24) ... etc

Has anyone come across this ?( ) notation before and knows what it means?

Thanks in advance.

Greg.

Grigorios Angelis

Grigorios Angelis wrote:
> Not exactly a VHDL question but hope someone knows the answer.
>
> When running a simulation earlier today and looking at the wave window of
> ModelSim I got the following reading when I tried to read the value of an
> integer variable: ?(23) ... ?(24) ... etc
>
> Has anyone come across this ?( ) notation before and knows what it means?
>
> Thanks in advance.

I've hit this too in Modeltech 5.8. Looks like an initialization thing.
Only have seen this with variables.

--
NAME: David W. Bishop INTERNET:

David Bishop

Hi there and thanks for replying.

After a lot of asking around I found the answer so I'm writing it here for
anybody else who's come across this.

In my (non-syntesisable) code I had declared a range constrained integer
variable (actually it had the same effect even when I switched that to a
signal) the upper bound of which was computed in the body of the
architecture... this means that ModelSim does not know the upper limit at
compile-time as this is computed during run-time.

This ?( ) notation (it is found in all version of ModelSim) means that
ModelSim does not (cannot) perform the check to see if the value is within
specified bounds, it just accepts it.

Greg

"David Bishop" <> wrote in message
news:2w30c.51671$...
>
>
> Grigorios Angelis wrote:
> > Not exactly a VHDL question but hope someone knows the answer.
> >
> > When running a simulation earlier today and looking at the wave window
of
> > ModelSim I got the following reading when I tried to read the value of
an
> > integer variable: ?(23) ... ?(24) ... etc
> >
> > Has anyone come across this ?( ) notation before and knows what it
means?
> >
> > Thanks in advance.
>
> I've hit this too in Modeltech 5.8. Looks like an initialization thing.
> Only have seen this with variables.
>
> --
> NAME: David W. Bishop INTERNET:
>

Grigorios Angelis