appCell demo library (add-on to CDNLive EMEA 2019 CUS-Techtorial V)

Hi,

I am still not sure about what exactly is appCell and how it is different from Classic pcell that we design?

Can we use appCell as an alternative for Pcell?

Also if anyone has any documentation on Cadence Pcell Designer Tool please Share, It will be Helpful

Thank & Regards,

Akshay Naik

Hi,

I am still not sure about what exactly is appCell and how it is different from Classic pcell that we design?

Can we use appCell as an alternative for Pcell?

Also if anyone has any documentation on Cadence Pcell Designer Tool please Share, It will be Helpful

Thank & Regards,

Akshay Naik

Hi Akshay,

The point of an appCell is that it operates on an existing layout (not just a layout, but most appCells so far have been layout-focused), whereas a PCell creates a layout variant from scratch based on a set of parameters. So put another way, when you instantiate a PCell, you give it a set of parameters and it creates (in memory) a new subMaster cellView for that variant (that combination of parameters), and then populates that subMaster with geometries, instances and connectivity based on the PCell code. With an appCell, you provide a set of parameters and a cellView to work on, and it then has access to the geometries, instances and connectivity that is already present and can modify the content or add additional content based on that.

With PCell Designer, you can then create methods for your appCell using the same user interface normally used for creating PCells, but with a different purpose. You can use the same geometric queries and high level commands to construct utilities. There's then a form you can use to publish the method as an appCell and choose what the form (if needed) looks like for your appCell.

The resulting appCell is then published into a library (so you don't need to ship SKILL code around) and there's a simple function call to execute the appCell method from your shipped library that can then be assigned to a bind key, menu or toolbar.

So I wouldn't say it's an alternative to a PCell - it's using PCell technology for creating layout (or schematic/symbol) utilities.

As for documentation, we have some conventional Cadence documentation that is currently under construction (it will then end up on support.cadence.com). In the meantime we do have two rapid adoption kits on support.cadence.com and we usually provide a PDF with some documentation/training to existing customers. I'm not sure what organisation you're from - but if you send me a friend request with your contact details I can ensure that we work with  you to provide that (note, this is not an invitation for everyone to send me forum friend requests - I normally ignore those as it's better to ask questions in the forums or log support requests; I don't have the capacity to respond to direct questions from the whole world!)

Regards,

Andrew.

Hi Andrew,

Thank You Very much for your quick response and detailed explanation on working and usage of appCell. This will surely help me and my team in exploring it and implementing it in our work.

Hello Akshay,

the appCell concept has been envisioned and developed to offer a powerful and user-friendly way to extent the capabilities of Cadence Virtuoso in addition to conventional SKILL/SKILL++ scripts. AppCells hereby utilize and benefit from the vastly enhanced PCell functionality that is provided by the Cadence PCell Designer tool (see below). Conceptually, appCells can be understood as 'apps' (therefore, the name 'appCells') similarly to the apps that most of us use on our smart devices. At first, it may seem odd to use PCell functionality to extend Virtuoso's functionality, but appCells benefit from all the capabilities of the Cadence PCell Designer programming environment. Their implementation, debugging, profiling and documentation is a lot faster and easier compared to conventional SKILL/SKILL++ source code development based on my experience.

While PCells require an instantiation in the schematic or layout view, appCells act as 'tool functions' that may modify your cell view based on their programmed functionality, provided parameters AND the content and context of the cell view(s) they are applied to. Contrary to PCells, appCells are not instantiated in cell views. However, they are added to a project in a classic lib/cell/view form and can be integrated in flows in multiple known ways, such as bind-keys, toolbar icons, menu entries etc. From a programmers perspective, an appCell is typically developed as a parameterizable PCell method that is then executed by end-users within the current cell view context. This is contrary to PCell instances that are executed in a separate and independent cell view context - my words :-).

To really understand the innovation potential provided by appCells, an understanding of the PCell Designer concept is highly beneficial. Among many other things, PCell Designer offers a rich set of built-in and user-extensible high-level commands and a PCell/appCell programming paradigm based on object orientation, data flow programming and functional programming.

You can find conceptual introductions to the visual PCell/appCell programming concept and several related concepts here:

Visual PCell Programming with Cadence PCell Designer (2013)
https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/company/Events/CDNLive/Secured/Proceedings/EU/2013/CUS04.pdf

Advanced Application of Cadence PCell Designer (2014)
https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/company/Events/CDNLive/Secured/Proceedings/EU/2014/CUS06.pdf

Hierarchical Module Design With Cadence PCell Designer (2015)
https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/company/Events/CDNLive/Secured/Proceedings/EU/2015/CUS02.pdf

Schematic and Symbol PCell Development with Cadence PCell Designer (2017)
https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/company/Events/CDNLive/Secured/Proceedings/EU/2017/CUS10.pdf

The PDF files referenced above provide a short overview of the appCell concept. They also contain a brief technical comparison of appCells and PCells (slide #30).

Please feel free to test the appCell approach yourself using the provided GPDK-045 based test cases. While the appCell examples provided above are layout-focused, I would like to point-out that appCells can be used to in schematic, symbol and layout views and from a flow perspective in any sequence and combination of them (e.g. generate schematics and symbols out of a given layout, place IO pads in the layout based on a given schematic or external file, ...). The resulting appCell/PCell code typically contains only a few code lines even for very complex tasks, which makes their development so efficient and convenient.

PS: An analogy for an appCell in the image editing world is a paint brush that manipulates parts of a picture based on given parameters, the region and the pixel neighborhood. You may have several generic and custom paint brushes at your disposal for your individual editing needs. PCell Designer would now allow you to let you create your own set of paint brushes, i.e. appCells, very easily.

Kind regards,
Goeran

Hi Goeran,

Thank you very much for your brief explanation on appCell. 

Also the document shared by you will be valuable for me in understanding the advance feature of Pcell Designer Tool. 

One query, Is appCell compatible only with gpdk045 or can it be used across other PDK from different Fab?

Thanks and Regards,

Akshay N

appCells can be used with any technology. Goeran's example library was specifically set up for gpdk045 to allow it to be easily shared, but there's no reason why your appCells can't be implemented for any technology.

Regards,

Andrew.

Hi Andrew,

Thank You for the information.

Regards,

Akshay Naik

Hi Akshay,

The appCells approach by itself is generic and not dependent on any technology.

The appCell demo lib provided above was developed by us using the gpdk045 to allow easy testing and evaluation for all Cadence users. The appCell examples can be ported to a different technology if you adjust the layer names of the the PCell code in PCell Designer. Layer names can be defined hard-coded or via PCell internal variables. In the latter case you would only have to adjust it once in your code or via a PDK release procedure. The provided appCell examples use different approaches for layer naming. A second location to check is the add_instance command in the examples which then has to point to the new MOS instances of your technology. A third location are the defaults used in the edits parameters form, which might differ between the gpdk045 and your technology of interest.

There are several ways of separating the logical code from the technology values and technology options, such as CDS techlib lookup, the usage of CDF code and/or the usage of an object oriented PCell approach using inheritance etc. We did not add this to our examples on purpose since our focus was here on the appCell concept.

Regards,
Goeran

Hi Goeran,

Thank you for this information. Really appreciate the quick response from you on this discussion.

Also the appCell demo provided by you is easily understandable given the reference documentation. 

I am well verse with designing Pcell using Pcell Designer Tool, where in I can design a complex Pcell. Would really like to implement appCell and have a hands on over it to understand its versatility. 

Thanks & Regards,

Akshay

Hi Andrew,

As told by you, I have sent you a friend request on forum with my mail ID. It would be really helpful if you could please share the said documentation on Pcell Designer tool over the mentioned Email ID?

Thank You,

Akshay Naik

Hi Akshay,

Sorry - I'm in the US this week and just hadn't got to it yet, I'll aim to send it today.

Andrew.