[myhdl-list] Re: VCD viewer ?

[Jan D. <ja...@ja...>]

Jean Demartini wrote:
> Hi all,
> 
> ISS (www.iss-us.com) has released a new version of its Wave VCD viewer. 
> This version functions quite properly... But the VCD files generated by 
> the traceSignals method are not strictly conformant to the IEEE specs 
> and some tools cannot parse these VCD files.
> 
> Some points:
> 1 - the declaration of a reg with a size > 1 is incorrect It lacks the 
> slice declaration. Ex. "$var reg 2 state[1:0] $end" is the correct 
> declaration instead of "$var reg 2 state $end". This point is easy to 
> solve in _traceSignals.py file.

Yes, looking at the original code it seems that something was
missing (the code makes a difference for the case size = 1 and
size > 1, but then does the same thing).

You mention the "VCD standard", do you have a reference for this? I
remember looking for a "standard" during implementation, but I only
found examples and explanations.

> 2 - the integer variable are declared as real 1 and then translated to 
> strings such as sXX and that is not allowed in VCD format. This point 
> too is not too difficult to solve by addind the adequate _printVcd 
> method in the signal object: file _Signal.py

The difficulty with integer is that the Python integer has an
"indefinite" bit width while the Verilog integer has a bit width
of 32. The current (non-standard) implementation would address that,
and a straight integer mapping won't. I agree though that this may be
more of a theoretical issue. In fact, the same issue exists already
in the Verilog conversion.

> 3 - It is rather easy, as above, to introduce the management of real 
> variables.

Right.

> 4 - but how to manage the enum variables which are valued by strings ?

Here the issue is that VCD doesn't support it, but the extended VCD
that gtkwave supports does. (This is mentioned in the manual). It is
remarkable that VCD became so popular without support for strings
(and therefore, enums). The best solution may be to support another
format that has this. I know that gtkwave also supports GTX (or GXT?)
but I don't know a lot about it. Does your viewer support other
formats that may be a candidate?

Regards, Jan

> 
> Has somebody an idea ?
> 
> JDem
> 
> Jean Demartini a écrit :
> 
>> Thanks a lot Günter for your help. Finallt GTKwave for Windows 
>> functions properly.
>>
>> For the information a the new users of GTKwave: the executable 
>> winwave.exe has to be launch in a DOS console window and is not an 
>> interactive GUI software. Then a user window is opened.
>>
>> Günter Dannoritzer a écrit :
>>
>>> Hi Jean,
>>>
>>> Jean DEMARTINI wrote:
>>>
>>>> Hi all,
>>>>
>>>> For many reasons I've to use MyHDL on a Windows platform (XP SP2). 
>>>> Python and MyHDL works perfectly. But has anyone knowledge of a 
>>>> working free VCD viewer onto Windows. Despite many effort, I've not 
>>>> succeded to use GTKwave and Wavevcd from ISS (beta downloadable at 
>>>> www.iss-us.com) does not recognize the VCD format generated by MyHDL 
>>>> (its is a drawback of the ISS viewer as the VCD format generated by 
>>>> MyDHL is quite correct) .
>>>>
>>>> Jean
>>>>
>>>>
>>>
>>> Have you looked into GTKWave?
>>>
>>>     http://www.cs.man.ac.uk/apt/tools/gtkwave/
>>>
>>> I have not used it with MyHDL, so I cannot commend on that.
>>>
>>> Here is a page that has a windows version available:
>>>
>>> http://www.geocities.com/SiliconValley/Campus/3216/GTKWave/gtkwave-win32.html 
>>>
>>>
>>> The windows version is an older version, but still works fine. 
>>> Actually I had recently a .vcd file that would work with the older 
>>> version and not with one of the new 2.0 pre releases.
>>>
>>> Hope that helps.
>>>
>>> Guenter
>>>
>>>
>>>
>>> -------------------------------------------------------
>>> SF email is sponsored by - The IT Product Guide
>>> Read honest & candid reviews on hundreds of IT Products from real 
>>> users..
>>> Discover which products truly live up to the hype. Start reading now.
>>> http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
>>
>>
>>
>>
>>
>> -------------------------------------------------------
>> SF email is sponsored by - The IT Product Guide
>> Read honest & candid reviews on hundreds of IT Products from real users.
>> Discover which products truly live up to the hype. Start reading now.
>> http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
> 
> 
> 
> 
> -------------------------------------------------------
> SF email is sponsored by - The IT Product Guide
> Read honest & candid reviews on hundreds of IT Products from real users.
> Discover which products truly live up to the hype. Start reading now.
> http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click


-- 
Jan Decaluwe - Resources bvba - http://jandecaluwe.com
Losbergenlaan 16, B-3010 Leuven, Belgium
     Using Python as a hardware description language:
     http://jandecaluwe.com/Tools/MyHDL/Overview.html