Pin Modeling

In previous releases of OpenAccess, strong and weak connections were modeled with pin groups, and pins could have a single oaFig. However, routers are more efficient when polygonal or rectilinear pins are decomposed into rectangles.

To address this, OpenAccess 2.2 introduces a new approach for modeling pins (oaPins).

oaPins have collections of zero or more
- Figures (oaPinFigs), which can be shapes, instances, or vias
- Routes (oaRoutes)
oaPinFigs on the same oaPin are strongly connected.
oaPins on the same terminal are weakly connected.
Terminals that must be connected at the next level of hierarchy can be added to a MUSTJOIN set.
oaPinGroups are no longer needed and have been removed.
oaInstPins are no longer needed and have been removed.

Pin Modeling Mapped to LEF

The following LEF representation demonstrates oaPinFigs that are strongly connected, and oaPins that are weakly connected.

PIN IN
 PORT RectA; RectB; END
 PORT RectC; RectD; END
END IN

Two metal rectangles that are part of the same LEF port are oaFigs on the same oaPin. In OpenAccess, the two rectangles are said to be strongly connected:

Both oaPins belong to the same oaTerm, which corresponds to the LEFpin “IN”. The pins are said to be weakly connected:

This is represented as follows in OpenAccess:

MUSTJOIN Sets

A MUSTJOIN set indicates that some connections within a master are incompletely implemented in the instantiating design. These connections must be completed for each instance. Terminals in a MUSTJOIN set must be connected at the next level of hierarchy. Each terminal in a MUSTJOIN set must come from a different, non-equivalent net.

The following LEF representation demonstrates MUSTJOIN sets.

PIN IN
  PORT  RectA; RectB; END
END IN
PIN IN.1
  MUSTJOIN IN;
  PORT RectC; RectD; END
END IN.1

This is represented as follows in OpenAccess:

Elimination of oaInstPin

The oaInstPin class was used by routes and parasitics in previous versions of OpenAccess. For a route ending at an instTerm of a terminal with multiple pins, oaInstPin specified which of those pins the route touched.

With multiple figs per pin in OpenAccess 2.2, oaInstPin is no longer sufficient.

In OpenAccess 2.2, routes and parasitics connect to instTerms.

You can use coordinates (oaPoint and layer) to distinguish between

Multiple pins per terminal
Multiple figs per pin

Routers and parasitic stitchers need to interpret the coordinates.

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