Clone Generation

Cloning is the ability to replicate a section of the layout, associated with a section of the schematic, in such a way that the new piece of layout material can be placed at more than one location, with each part preserving the hierarchical structure of the design. Cloning differs from synchronous copying in that the cloned structure maintains its schematic correspondence and inherits the connectivity information, while a synchronous copy does not maintain any schematic correspondence.

Layout XL also supports clone creation by setting a Clone Family constraint in the Constraint Manager. For more information, see Instance Cloning Using a Clone Family Constraint and the cloneFamily option described under Constraint Manager Toolbar in Virtuoso Unified Custom Constraints User Guide.

Cloning can help you lay out:

• Datapath bit slices, datapath and memory control blocks with identical logic cones, programmable logic structures, and other arrayed and iterated structures in device-level and gate-level custom digital design.
• Groups of analog/mixed signal components with identical constraints (for example, current mirrors, cascode stages, differential pairs, and other isomorphic structures).
• Instances of the same symbol master – or instances with the same logic but with differing parameters and hence a different symbol master – that have a flat layout representation.
• A chained set of devices or a part of the chain.
• Members of a Clone Family constraint.
• Transparent instances in the layout such that the generated clone is also a transparent instance.

The section of the schematic or layout that is used as a template for the clone is called the clone source. The section of the schematic that is to be implemented by replicating the source is the clone target. The result of replicating the clone source to implement the clone target is the clone. For the clone source to be used to generate a clone target, the clone source should be bound.

You can use multiple connectivity sources and multiple layout cellviews, including layout cellviews that are open in read-only mode, to generate clones. The clone source that you select can comprise devices, pins, and (if selected from the layout canvas) interconnect structures such as wires and path shapes. You can also clone components that are implemented as one-to-many relationships defined using the mfactor property on a schematic instance.

A source structure is considered invalid for cloning if it includes:

• any device that is part of a user-defined many-to-one binding (specified using the Define Device Correspondence form).
• a folded device that has only some of its folds selected for cloning.
• instances that do not exactly match the Clone Def of a Clone Family constraint.
• An instance that is neither bound nor ignored, which makes the device an invalid clone dummy device.
  • For a device to be considered as a valid clone dummy device, it must either have one of the Layout XL ignore properties or a physOnly attribute set.
• One or more group arrays.

In each case, a warning appears in the CIW explaining the error and the corrective action.

Related Topics

Synchronous Copy Generation

Transparent Layout Hierarchy Generation

Mfactored Component Cloning

Exact and Non-Exact Matches for Cloning

Types of Clones

Instance Cloning

Define Device Correspondence Form

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