Modgen Device Abutment

Modgen supports abutment of MOSFET member instances. When you abut a device, Modgen remains aware of its connectivity and might flip the device to correctly abut it.

You can also abut dummy devices to other devices and dummies. Internally, the dummy device net might be changed from the default specified in the Dummy Options form, but if the dummy device is removed from abutment, the net reverts to the default. When two instances are abutted, body contacts between them are deleted.

Modgen abutment uses the Layout XL chaining engine. Therefore, the abutment results are subject to the settings of the Layout XL chaining environment variables. Notable examples are chainMirror and chainMirrorEquivOrients. These environment variables are enabled by default, and may therefore result in unintended changes to the orientation of instances.

Prerequisites for Modgen Device Abutment

The devices to be abutted must be registered as component types. It addition to abutment, this is a key requirement for operations such as chaining and folding devices, identifying pseudo-parallel nets, and identifying devices and structures using the Circuit Prospector assistant (this is a schematic XL feature) in Schematic view.

If the devices are not registered in the PDK, use one of the following methods to register devices as component types:

• Use the ciRegisterDevice function.
• Use the cph.lam file to assign the devices to component types NMOS, PMOS, NFIN, or PFIN.
• Use the Component Type mode of the Configure Physical Hierarchy window to assign the devices to component types NMOS, PMOS, NFIN, or PFIN.
  
  The CPH settings must be done only once on a design before invoking the Modgen Editor.

Related Topics

Library and Attributes Mapping File Syntax

Defining a Design-Level Component Type