Re: More VHDL issues..

"rickman" <> wrote in message
news:...
> I added a variable to calculate a time for a wait statement in a
> testbench and am not getting this error from ModelSim...
^^^ now??

>
> Signal arm_command is read by the VITAL process but is NOT in the
> sensitivity list
>
> This is the line of code producing the error...
>
> WaitTime := (ARM_command.RelTime - (now - CurrentTime));
>
> I follow this up with a check for negative values before using in
the
> wait. ARM_command is a signal and WaitTime and CurrentTime are
> variables. And of course all these objects are of type time. This
same
> calculation done directly in the wait statement gives no error.
>

It sounds like Modelsim is confused. Is it actually an error, or just
a warning? Having a signal read that is not in the sensitivity list
is not an error. Can you disable Modelsim's synthesis checks?

If it's a warning, just ignore it.

If it's an error, it sounds like a bug.

regards

Alan

p.s. I know it's nothing to do with this error, but I'd check for
negative values before assigning, just because I am paranoid (!). In
particular I wonder what happens if you assign a negative time value
to a variable of type time?
e.g.

assert ( (ARM_command.RelTime - (now - CurrentTime)) >= 0 ns )
report "negative time value";

waittime := ...

p.p.s.
Reading the LRM shows I really am being paranoid, as type TIME is
guaranteed to include the range -2**9+1 to 2^9-1, so negative
time values in variables of type TIME are ok.





--
Alan Fitch
Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * Perl * Tcl/Tk * Verification * Project
Services

Doulos Ltd. Church Hatch, 22 Market Place, Ringwood, Hampshire, BH24
1AW, UK
Tel: +44 (0)1425 471223 mail:

Fax: +44 (0)1425 471573 Web:
http://www.doulos.com

The contents of this message may contain personal views which are not
the
views of Doulos Ltd., unless specifically stated.

Alan Fitch

Alan Fitch wrote:
>
> "rickman" <> wrote in message
> news:...
> > I added a variable to calculate a time for a wait statement in a
> > testbench and am not getting this error from ModelSim...
> ^^^ now??

Yes, now, not "not".

> >
> > Signal arm_command is read by the VITAL process but is NOT in the
> > sensitivity list
> >
> > This is the line of code producing the error...
> >
> > WaitTime := (ARM_command.RelTime - (now - CurrentTime));
> >
> > I follow this up with a check for negative values before using in
> the
> > wait. ARM_command is a signal and WaitTime and CurrentTime are
> > variables. And of course all these objects are of type time. This
> same
> > calculation done directly in the wait statement gives no error.
> >
>
> It sounds like Modelsim is confused. Is it actually an error, or just
> a warning? Having a signal read that is not in the sensitivity list
> is not an error. Can you disable Modelsim's synthesis checks?
>
> If it's a warning, just ignore it.
>
> If it's an error, it sounds like a bug.
>
> regards
>
> Alan
>
> p.s. I know it's nothing to do with this error, but I'd check for
> negative values before assigning, just because I am paranoid (!). In
> particular I wonder what happens if you assign a negative time value
> to a variable of type time?
> e.g.
>
> assert ( (ARM_command.RelTime - (now - CurrentTime)) >= 0 ns )
> report "negative time value";
>
> waittime := ...
>
> p.p.s.
> Reading the LRM shows I really am being paranoid, as type TIME is
> guaranteed to include the range -2**9+1 to 2^9-1, so negative
> time values in variables of type TIME are ok.

The possibility of being negative was why I was using a variable instead
of just sticking it in the wait statement. I thought it would be better
to calculate it once and then test it and set to zero if negative. So
now I have to do the calculation twice.

I am getting the same error from a different assignment now. The common
point is that a signal is on the right hand side of the assignment and a
variable is on the left. I am using the variable assignment operator,
":=". This is reported as an error, not a warning.

Last_Bus_Action := Bus_Command.Bus_Action;

In both cases, part of the right hand expression is an element in a
record. The error reports the record "Bus_Command" as missing from the
sensitivity list, not the element! Could the VITAL process have a bug
in regards to dealing with record elements? This doesn't sound likely
to me. But then I don't even know what the VITAL process is.

Maybe I need to contact Mentor about ModelSim.

--

Rick "rickman" Collins


Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX

rickman

<snip>
> >
> > p.p.s.
> > Reading the LRM shows I really am being paranoid, as type TIME is
> > guaranteed to include the range -2**9+1 to 2^9-1, so negative
> > time values in variables of type TIME are ok.
>
That should have been -2**31+1 to 2**31-1, sorry.

> The possibility of being negative was why I was using a variable
instead
> of just sticking it in the wait statement. I thought it would be
better
> to calculate it once and then test it and set to zero if negative.
So
> now I have to do the calculation twice.
>
OK, sounds sensible.

> I am getting the same error from a different assignment now. The
common
> point is that a signal is on the right hand side of the assignment
and a
> variable is on the left. I am using the variable assignment
operator,
> ":=". This is reported as an error, not a warning.
>
> Last_Bus_Action := Bus_Command.Bus_Action;
>
> In both cases, part of the right hand expression is an element in a
> record. The error reports the record "Bus_Command" as missing from
the
> sensitivity list, not the element! Could the VITAL process have a
bug
> in regards to dealing with record elements? This doesn't sound
likely
> to me. But then I don't even know what the VITAL process is.
>
That is weird. I thought that VITAL was a label you'd used in your
code, e.g.

vital: process...

But if it's not?

If it's vital as in "VITAL - VHDL Initiative Toward Asic Libraries"
then
I'd only expect to see it referred to if you were doing back-annotated
gate level simulation?

> Maybe I need to contact Mentor about ModelSim.
>
Sounds like a good idea.

regards

Alan


--
Alan Fitch
Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * Perl * Tcl/Tk * Verification * Project
Services

Doulos Ltd. Church Hatch, 22 Market Place, Ringwood, Hampshire, BH24
1AW, UK
Tel: +44 (0)1425 471223 mail:

Fax: +44 (0)1425 471573 Web:
http://www.doulos.com

The contents of this message may contain personal views which are not
the
views of Doulos Ltd., unless specifically stated.

Alan Fitch

On Tue, 05 Aug 2003 12:18:31 -0400, rickman <>
wrote:

>Alan Fitch wrote:
>>
>> "rickman" <> wrote in message

>> > This is the line of code producing the error...
>> >
>> > WaitTime := (ARM_command.RelTime - (now - CurrentTime));
>> >

>> It sounds like Modelsim is confused. Is it actually an error, or just
>> a warning? Having a signal read that is not in the sensitivity list
>> is not an error. Can you disable Modelsim's synthesis checks?

>I am getting the same error from a different assignment now. The common
>point is that a signal is on the right hand side of the assignment and a
>variable is on the left. I am using the variable assignment operator,
>":=". This is reported as an error, not a warning.
>
> Last_Bus_Action := Bus_Command.Bus_Action;

If that's the case, then assigning the record field to an intermediate
signal would probably "fix" it. Not nice, but as an expedient to (a)
keep moving and (b) home in on the real problem, maybe worth trying.

-- parallel signal assignment
tempAction <= Bus_Command.Bus_Action;

-- within process or whatever
Last_Bus_Action := tempAction;

Assuming it works, then a support call to ModelSim, asking why one
works, but not the other, would be very worthwhile.

- Brian

Brian Drummond

Brian Drummond wrote:
>
> On Tue, 05 Aug 2003 12:18:31 -0400, rickman <>
> wrote:
>
> >Alan Fitch wrote:
> >>
> >> "rickman" <> wrote in message
>
> >> > This is the line of code producing the error...
> >> >
> >> > WaitTime := (ARM_command.RelTime - (now - CurrentTime));
> >> >
>
> >> It sounds like Modelsim is confused. Is it actually an error, or just
> >> a warning? Having a signal read that is not in the sensitivity list
> >> is not an error. Can you disable Modelsim's synthesis checks?
>
> >I am getting the same error from a different assignment now. The common
> >point is that a signal is on the right hand side of the assignment and a
> >variable is on the left. I am using the variable assignment operator,
> >":=". This is reported as an error, not a warning.
> >
> > Last_Bus_Action := Bus_Command.Bus_Action;
>
> If that's the case, then assigning the record field to an intermediate
> signal would probably "fix" it. Not nice, but as an expedient to (a)
> keep moving and (b) home in on the real problem, maybe worth trying.
>
> -- parallel signal assignment
> tempAction <= Bus_Command.Bus_Action;
>
> -- within process or whatever
> Last_Bus_Action := tempAction;
>
> Assuming it works, then a support call to ModelSim, asking why one
> works, but not the other, would be very worthwhile.
>
> - Brian

I already have a work around and have sent the problem to Xilinx (Mentor
does not support the Starter Edition). But thanks.


--

Rick "rickman" Collins


Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX

rickman