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The Cell Properties Button: Edit Cell properties

The Cell Properties button in the Edit Menu brings up the Cell Property Editor, which is used to view and manipulate properties of the current cell. It is a simplified version of the Property Editor which is used to manipulate the properties of objects contained within the current cell.

The Cell Property Editor contains buttons to add, edit, and remove cell properties. In general, cell properties are assigned internally and can not be modified. The exceptions are the properties listed in the Add menu and further discussed below. Pressing the Add button brings up a pop-up menu containing entries corresponding to properties that can be set or modified by the user. Only the properties that are applicable to the current mode (physical or electrical) are active.

In physical mode, the entries listed below are available, allowing modification of physical cell properties (see D.1).

The any entry allows an arbitrary property to be assigned to the cell. The user will be prompted for a number and string for the property. These are arbitrary, however there are certain numbers that are reserved by Xic and will not be accepted. Xic will not use these properties, but they may be important for interfacing to third-party applications.

The flags entry is used to set flags in the cell, notably the OPAQUE flag which causes the cell contents to be ignored during extraction.

The flatten property applies to electrical and physical cells and instances. It is used during association and LVS to determine if the contents of the instance master should be logically promoted into the containing cell (see 16.4). Although Xic can handle most hierarchy differences automatically and transparently, this property may be used when needed to force proper behavior.

If a flatten property has been applied to the master cell, then instances of the cell will be flattened, unless the instance also has the flatten property applied, in which case the instance will not be flattened. If the master does not contain a flatten property, then and instance will be flattened only if the instance has a flatten property applied. Thus, the flatten property of an instance reverses the effect of a flatten property applied to the master.

The FlattenPrefix variable, and equivalently the Cell flattening name keys entry area in the Net and Cell Config page of the Extraction Setup panel from the Extract Menu, provide another means of causing instances of cells to be flattened.

The pc_params entry is used when defining parameterized cells (pcells, see 5.1). It is used to set or modify the parameter list associated with the pcell.

The pc_script entry is used when defining parameterized cells. It is used to set or modify the script which implements the pcell features.

In electrical mode, the following properties can be set from the Add menu.

Selecting the param button allows a param property to be added to the cell. The param property provides support for the subcircuit parameterization feature of WRspice (see the description of the .subckt line). The use of parameterization is briefly described in D.3.

Selecting other allows an other property to be added to the cell. These have no meaning to Xic, but might be of use to the user. Any number of other properties can be added.

Adding a virtual property will prevent the cell from being included in netlist output, most importantly SPICE output. The cell becomes a ``placeholder'', and the actual .subckt text, which is required to satisfy references, is included in the SPICE file by another means. For example, the cell might represent an opamp, and a .include line can be used to bring in the .subckt block representing the opamp, from a vendor model file.

See the description of the flatten property in the physical Add menu properties list above. The property has the same use in electrical mode.

This property can be applied to device masters. The only effect is that when Xic is generating SPICE output, instances of devices with this property will have an `X' prepended to the device name, thereby making the device appear as a subcircuit call in SPICE. This enables a component, such as a resistor, to be modeled by a subcircuit that may contain dependent sources to model nonlinear behavior. The subcircuit definition is likely provided in the SPICE models from a vendor or foundry.

For device cells, as would appear in the device library file, model, value, and param properties can be applied. When a device instance is placed, the instance will inherit copies of these properties. Instances of non-devices do not inherit a param property from the master. The model and value properties can not be applied with the Cell Properties Editor, but can be added to device masters with the Library Device Parameters panel (see 8.5).

next up previous contents index
Next: The Modify Menu: Modify Up: The Edit Menu: Edit Previous: The Delete Button: Delete   Contents   Index
Stephen R. Whiteley 2017-03-22