[Magic-dev] Broken Nets

[Rajit Manohar]

Hi,

Would it be possible to get a copy of the .mag file that causes the 
problem? When we went from 6.5 -> 7.1, all that happened was various 
bug-fixes from multiple groups were merged, and some extensions to the 
command interpreter were included. So the fact that it works in 6.5 but 
not 7.1 is interesting...

Regards,

-Rajit

On Mar 17, 2005, at 12:41 PM, Satpal Singh wrote:

> Dear Tim,
>
> The problem of broken nets disappears if I extract the design using 
> the same technology file (SCN3ME_SUBM.30.tech27) but use magic 6.5 
> instead of 7.1
>
> The problem also disappeared when using magic 7.1, I used the option, 
> "extract no capacitance".
>
> The problem of broken nets was that on some designs, it appears to be 
> random, on extraction and ext2spice, one net is broken into 2 nets, 
> which leads to failure of simulation. In reality, there is only one 
> net as can be verified by highlighting the net on the layout. Also 
> using the "getnode" by selecting different portions of the net, the 
> same node name is returned, however the "ext all" followed by 
> ext2spice shows 2 nets.
>
> It also seems that sometimes by shifting the position of the label 
> with the same cell, or shifting part of the track in the layout, the 
> problem goes away while it may appear at other areas.
>
> I had also extracted the design using the standard scmos tech file 
> with magic 7.1, and I still had the same nets shown as 2 nets, so the 
> problem does not seem to be tech file specific.
>
> I am not a programming expert, but I know enough to install Linux and 
> magic, I have used magic 6.4 and 6.5 for 10 years now and have done 
> several designs, so I do not think I am doing something terribly wrong 
> (or may be I am and I was just lucky all along !! ).
>
> Do you recommend that I dump magic 7.1 (which I had downloaded only 
> recently) and move on to  higher versions, my choice of 7.1 was 
> because it said its a stable version.
>
> I would greatly appreciate your advise.
>
> Regards,
> Satpal Singh
> Prime Circuits Inc. / GSFC
>
>
>
>
>> X-POP3-Rcpt: singh at primecircuits.com
>> Date: Tue, 15 Mar 2005 11:56:44 -0500
>> From: "R. Timothy Edwards" <tim.edwards at multigig.com>
>> To: singh at primecircuits.com
>> Subject: RE: Broken nets
>> Cc: magic-dev at csl.cornell.edu
>>
>> Dear Satpal,
>>
>> > I recently downloaded Magic 7.1 and am using the tech file
>> > SCN3ME_SUBM.30.tech27 to design for AMI 0.5 um process. On 
>> extraction
>> > (ext all) and running ext2spice to generate a netlist, I 
>> occasionally
>> > (not always) find that a single net in the layout has been broken
>> > into 2 different nets in the spice file, this leads to the failure 
>> of
>> > simulation.
>>
>> There are a number of reasons this sort of thing can occur.  The
>> reason that they seem "random" is that the extractor is not to
>> blame---the extraction algorithm in magic is surprisingly robust---
>> but there are a number of other subtle errors that can occur.
>>
>> One of them, which may have caused at least one of your broken
>> simulations, is that labels can get copied from one cell into another,
>> and end up on separate layer types (e.g., metal1 and metal2) that
>> are not connected.  Extraction will short nets having the same
>> (labeled) name.
>>
>> Usually it is a good idea to ensure that the circuit layout is correct
>> by doing LVS (layout vs. schematic) as well as extraction+simulation.
>>
>>
>>                                         Regards,
>>                                         Tim
>
>
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