GDS stream version

This is covered in the <ICinstDir>/doc/transref/transref.pdf (or <ICinstDir>/doc/transrefOA/transrefOA.pdf if using IC61X versions). There is a section about Stream Format, and within that a section called "Differences in Stream Format Versions". I've cut and pasted the relevant (slightly edited) section below. Note that in practice I've not seen anyone including the features introduced in versions 4/5/6. With version 7, it's primarily the limits being removed, and many people ignored the limits even in earlier stream versions. Given that even version 6 dated from Calma days (so more than 20 years ago, I think), it's usually not worth worrying about!

Differences in Stream Format Versions

There are five available versions of stream format, version 3, 4, 5, 6 and 7. Stream versions
4 and 5 are the same. The records listed in the above section are a combined list of all the
records supported by the various stream formats. The various versions provide support for a
subset of records present in this list.
The Stream format is usually broken down into 4 versions:

• Stream format version 3 supports basic geometric information. From the list of supported stream records, Stream 3.0 only supports up to record 44.
• Stream format version 4 or 5 provides support for geometric information along with supporting new types in gdsII 4, such as nodes, ports, template, plex data. From the list of supported stream records, version 5.2 supports up to record 56.
• Stream format 6, has some additional information for a product called "Custom Plus" that includes things like "attach file" and "lib access control lists". From the list of supported stream records, version 6.0 supports up to record 59.
• The last format version is generically called 7 which has lots of the limits removed. In this version, polygons can have more than 200 points, more than 64 layers and datatypes are supported, and more than 10 levels of hierarchy are supported. From the list of supported stream records, version7 supports all the records.

Stream 6 was very GDSII specific so not many non-Calma reader/writer applications handle
it. Simple applications deal with Stream 3 (basic geometries), more advanced deal with 4/5
and general purpose remove limitations and can handle upto version 7.

Regards,

Andrew

Hi Anna,

So does that mean you're using a Calma GDS? People often use the term "GDS" to refer to the format, when the format is actually "stream format".

Normally the tool that writes out the stream file defines what version it uses, but in practice it's unlikely to matter what version was used, since the new features in version 4-6 are not used in practice as far as I'm aware. The document I referenced gives the full specification of the stream format.

In the Cadence IC tools you can choose to write out in versions 3, 5, or 6. Not that I think it makes much difference (the default is 5).

So I didn't really understand your last  question - or even if it was a question!

Regards,

Andrew.

Hi Andrew,

Thanks a lot for your answers. Let me re-phrase my question:

I'm using the Laker tool for streaming in the GDS. So I am expecting to see in the resulted log files all the info on the stream file.

Could you please let me know whether the following is an output of the specific tool? Here I see the stream file format corresponding to the described format in the document transrefOA.pdf. Is this Cadence specific format? As far as I understand this shows that I have a stream format version is 6. 

0000000 0006 0002 0003 001c 0102 006c 0006 000a %

But I cannot see the version while streaming i the GDS with Laker tool.

Thanks a lot,

Anna

Well, first of all, the stream format was originally created by Calma. It was then picked up by Valid, and that in turn became part of Cadence. So the format is owned (at least I believe it still is) by Cadence, and that's why the format is documented in those documents. It does not mean that there is a Cadence-specific flavour of stream format - it has not been changed for an extremely long time.

As for issues with reading it into Laker, it's a bit odd posting such questions to a forum on the Cadence web site, given that Laker is nothing to do with Cadence. If you don't see info on the version from Laker, that's something to raise with Springsoft, I'd have thought. I cannot tell by looking at a sequence of a small number of bytes (or even a large number of bytes!) which tool wrote it out. In fact there is a record, LIBNAME, which is sometimes (but not always used) to give some indication of the tool used to write the data, but even that's no guarantee. Regardless of this, it really shouldn't matter what tool wrote it, or even what version it was.

Regards,

Andrew.

Hi Andrew,

 Thanks a lot for the detailed info.

I tried both with Virtuoso also and see no difference. So, as far as I understand from your last email the tool does not have any impact on the stream version.

As you suggested I'll try to choose to write out in the evrsion I need.

Thanks again,

Anna