How to use a DEF in SoC Encounter

Hi,

I obtained a DEF file as well as a netlist file of a module. Now I
want to use the placed cells information in the DEF file in the SoC
Encounter to layout the cells. My question is that if there is a way
can quickly translate the placed cell information in the DEF file to a
placement file in SoC Encounter. There seems no direct connection
between a DEF and a placement file for the existing examples I am
having now.

Thanks.

 

I don't use Encounter, but I thought the DEF (Design Exchange Format)
file can contain placement information that you can read directly into
Encounter? Maybe you could find the cadence installation directory,
and there should be some pdf files for the various tools that can be
very helpful.

 

Hi,

There is no need to convert it to a .place file. Just import the design as you would do for a normal
flow, then load the DEF file, that should update the floorplan, placement and routing as it is in
the DEF.

Stéphane

 

Hi Stephane,

I know I could just import the DEF directly. However, I know the DEF
needs to be modified, i.e., hand placing cells, anyway regardless
whatever method I import it. So, the need of editing the DEF urges
such demand that it is easier to work on the text format of the DEF
rather than later on modifying the GUI layout. Therefore, if there is
a way to translate the DEF into a placement file, that will be
wonderful.

I know this may not seem a conventional approach but it is useful to
know these tricks too.

Thanks.

 

I really do not get it, what you want to do. Why do you want a .place file ? Anyway, the .place file
format is an internal encounter format, I do not think it is documented anywhere, and it's therefore
very doubtful that you will find any way to create one except going through encounter itself (look
for savePlace command).

I'd say, if you need to edit the .def file, then you're probably attacking your problem the wrong
way. If there's a good reason, I do not understand why you can't do all the .def tweaking before
importing it.

Stéphane

 

I know it is hard to see the reason for most. Here is a simple one: I
don't know have access to the DEF at all. It arrives as it is. The one
who generates tthe DEF has bigger problem to change the DEF. So the
load comes down to the .place file.

Anyhow, it seems there is no easy way to do that from your
discussions. Thanks.

 

I guess you think text editing of placement files are easier than def
files? I am not sure why you would think that. DEF is also a text file
which is quite easy to edit especially in terms of manually placing
the cells or writing a script to place them. When you receive the DEF
you can do all your tweaking/placing and the import it into the
design.

Another option is to read the DEF into the design and then export a
placement file without any intermediate changes to capture the
placement info into the def to the place file ie using SOC as a
conversion tool. Then you'd work on the place file and read it back
into the design. Why don't you modify the DEF instead?

 

This discussion gets to a more interesting point so I would go ahead
to dig into in a little bit more to reveal my need. Here is an
example:

Suppose a top level model has only two inverters and a black box
model. The black box model is a big one. Then a DEF is generated after
synthesis. For some reasons the synthesis guy can't change the
blackbox (location, orientation etc) easily on his side, i.e.,
textually. However, the DEF information on the two inverters are
right. On my side, I don't have the synthesis information either. But
we agree that the blackbox needs to be changed in actual layout while
remaining the relative placement of the two inverters. In short, the
DEF information needs to be modified partially. Because of this
partial modification, all absolute coordinates in the DEF file are not
right. What I try to do is to find a way to remain the two inverters
relative location and translate into the new place file.

Mk's option that modifying the DEF sure works. But this modification
is almost blind: I don't visulize the right location of the blackbox
and new placement of the two inverters. So I had my OP that indeed
about this problem: how to extract part of the DEF information to a
place file, given the condition that the extraction is only partially?

The way I use now is exactly what Stephane said: import the DEF into
Encounter and manually change the blackbox location as I need it. It
works but I wonder if there is other ways can that easier.

Thanks a lot for all your inputs.