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From: Nial Stewart on 10 Mar 2010 04:49
> Ok, but when I'm debugging, I often need to look at intermediate
> signals to see where the problem is coming from. It would be great to
> not have to rerun the simulation to do that. There is more than once
> that I added some signals only to find that the problem took a
> slightly different curve than the one I expected and I have to add
> more signals. In the end I may have to run the simulation 10 or more
> times before I see the problem.

Aye, this wouldn't be uncommon if I'm tracing a fault in a reasonably
complex design.

It's a big selling point for Aldec if you don't need to re-run a sim to
add more signals. I have had a few simulations that take 10 minutes to
get to the point I'm interested in so this could have saved a _lot_ of
time.

How much is an Active HDL license (�GBP) approx ?


Nial.



From: Jonathan Bromley on 10 Mar 2010 04:55
On Wed, 10 Mar 2010 09:49:28 -0000, "Nial Stewart" wrote:

>> Ok, but when I'm debugging, I often need to look at intermediate
>> signals to see where the problem is coming from. It would be great to
>> not have to rerun the simulation to do that. There is more than once
>> that I added some signals only to find that the problem took a
>> slightly different curve than the one I expected and I have to add
>> more signals. In the end I may have to run the simulation 10 or more
>> times before I see the problem.
>
>Aye, this wouldn't be uncommon if I'm tracing a fault in a reasonably
>complex design.

ModelSim lets you do this too - it costs disk space and
simulation speed, of course, but may still be worth it for
tough debug:

log -r /*

Now *everything* goes in the waveform log file, and
you can add any signal you want to the waveform retrospectively.

>It's a big selling point for Aldec if you don't need to re-run a sim to
>add more signals. I have had a few simulations that take 10 minutes to
>get to the point I'm interested in so this could have saved a _lot_ of
>time.

Yup. The log does introduce an overhead, but it's unlikely to be
worse than a factor of 2 or 3, so likely to be a win if you
initially don't know where to start looking.
--
Jonathan Bromley
(not connected with Mentor, but does use ModelSim quite a lot)
From: Nial Stewart on 10 Mar 2010 05:20
> ModelSim lets you do this too

I need a smiley for a red face

:-0

I started using Modelsim 15 odd years ago and am still using it in
the same way I 'picked it up'. I have often wondered if I'm
missing out on productivity enhancements.


> - it costs disk space and
> simulation speed, of course, but may still be worth it for
> tough debug:
>
> log -r /*
>
> Now *everything* goes in the waveform log file, and
> you can add any signal you want to the waveform retrospectively.
>
>>It's a big selling point for Aldec if you don't need to re-run a sim to
>>add more signals. I have had a few simulations that take 10 minutes to
>>get to the point I'm interested in so this could have saved a _lot_ of
>>time.
>
> Yup. The log does introduce an overhead, but it's unlikely to be
> worse than a factor of 2 or 3, so likely to be a win if you
> initially don't know where to start looking.


Even debug of small modules usually takes a few iterations so this
might be a useful 'default' simulation style when using the GUI for fault
tracing. I presume for smaller designs the overhead is negligable and it's
more likely to pay off for bigger designs.

Thanks Jonathan.

(Perhaps I should RTFM).

Nial.


From: Jonathan Bromley on 10 Mar 2010 06:09
On Wed, 10 Mar 2010 10:20:15 -0000, "Nial Stewart" wrote:

>(Perhaps I should RTFM).

Nah. That would spoil all the fun, thrill of
the chase, etc, etc.

Anyhow, there's just too much of it. Try this
entertaining little experiment.

1) Open a vanilla Tcl shell (if you have Tcl
installed). Ask it how many commands it
knows about:
llength [info commands]
The answer is about 86, depending on version.

2) Try the same in ModelSim's Tcl console.
Be very, very afraid.
--
Jonathan Bromley
From: Alan Fitch on 10 Mar 2010 06:49
Nial Stewart wrote:
>> ModelSim lets you do this too
>
> I need a smiley for a red face
>
> :-0
>
> I started using Modelsim 15 odd years ago and am still using it in
> the same way I 'picked it up'. I have often wondered if I'm
> missing out on productivity enhancements.
>
>
>> - it costs disk space and
>> simulation speed, of course, but may still be worth it for
>> tough debug:
>>
>> log -r /*
>>
>> Now *everything* goes in the waveform log file, and
>> you can add any signal you want to the waveform retrospectively.
>>

I had a quick look in aldec, and it has a command

log -r *

According to the help this is a synonym for

trace -r *

There are also various settings on the Trace/Debugging tab to do with
how Aldec preserves the signals you've added to the wavefrom window,

regards
Alan

<snip>

>
> (Perhaps I should RTFM).
>

That's what I did :-;



--
Alan Fitch
Senior Consultant

Doulos � Developing Design Know-how
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Doulos Ltd. Church Hatch, 22 Marketing Place, Ringwood, Hampshire, BH24
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