Virtuoso XL Layout Editor User Guide

Editing Your Layout with Virtuoso XL Layout Editor

If the two pins are on the same net, the instances are automatically abutted.

If the two pins are on different nets but auto-permutation of one or both of these pins will bring two pins in the same net into contact, the pins are automatically permuted and the two instances are abutted.

After the abutment takes place, the alterations to the cell that you specified in the pcell abutment parameters take place.

The abutment system moves only one instance to abut two cells. Of two instances that can be abutted, it chooses to move

1.A selected cell over a cell that is not selected

2.A cell that is not already abutted over a cell that is already abutted

Setting Component Types

You control how components are assigned to rows, and their chaining and folding parameters, by defining component types. You set the component type using the Edit Component Types form associated with the Design – Component Types command.

If you edit component types created in IC 4.4.6, using an editor in IC 5.0.0 or later, the data will be saved a in a new format that is incompabitle with IC 4.4.6.

About Component Types

Component types are part of the library or cell information for cells in which components are placed. You can define component types at the library level, if all cells in the library share the same types, or you can define component types for the individual cells that will contain the placed components.

The purpose of component types is to identify the NMOS and PMOS transistor cells and set their parameters for device chaining and folding.

Virtuoso XL Layout Editor User Guide

Editing Your Layout with Virtuoso XL Layout Editor

MOS Transistor Stacking and Folding Parameters

MOS transistors that are candidates for chaining and folding need to be identified in the Edit

Component Types form described in the Defining Component Types form (and have certain parameter values set) before you generate layout.

Use the following parameters in the NMOS or PMOS type definitions to control device stacking and folding during placement. You must set the lxDeviceWidth and lxMaxWidth parameters; the other parameters are optional.

Note: Terminal names are not case sensitive.

Fold Threshold The maximum width beyond which devices of type NMOS and PMOS must be automatically folded. This parameter needs to be set even if the devices will not be folded.

This value applies globally to all devices within the scope of the component type definitions (the library containing the current cell, or just the current cell). You can override this value using the layout generation commands Gen from Source and Pick from Schematic. In the Placement Style form, you can override lxMaxWidth by setting PMOS Width Threshold and NMOS Width Threshold.

Virtuoso XL cannot accurately enforce the value of lxMaxWidth unless all device widths and all lxDeviceWidth values are specified consistently; for example, all in meters (10um is 1-e-5) or in all in user units (10um is 10).

Source Terminal A list of instance terminal names corresponding to the MOS transistor source terminal. The default names are source and S. If you use different names, define this parameter and set its value. For example: ("src" "sour").

Defining Component Types

Setting the component types in this form sets the lxComponentType parameter.

1. Select Design – Component Types.

Virtuoso XL Layout Editor User Guide

Editing Your Layout with Virtuoso XL Layout Editor

The Edit Component Types form appears.

2.From the Scope radio buttons, choose the scope of the component types you want to create:

The current cell

Virtuoso XL Layout Editor User Guide

Editing Your Layout with Virtuoso XL Layout Editor

The current library

The reference librarynet

Important

The Ref Libs settings are read first. If there are noRef LIbs settings, then Library settings are read next. Current settings will override LIbrary and Ref Libs settings.

3.In the Type field, do one of the following:

Type in a name for a new type and click Add.

Note: Do not assign a type to more than one component master.

Typical types for a MOS device library might include NMOS, PMOS, and CAPACITOR. Type names may be any string.

Important

Type names must be upper case.

Select a type from the cyclic field.

4.Populate the Components in Type list by doing one of the following:

Click on the library cells or type in the information in the text field to highlight the cells in the Cells in Design list. Select the >>> button to move them into the

Components in Type list.

Select the cells in the layout and click Add Selected Components to move them into the Components in Type list

Note: The addition of instances are not supported in component types. If you try to add an instance and then click Add Selected Components a warning is issued; “We no longer support the addition of instances into component types”. Instance component types are removed from a design when the layout is regenerated.

Or, if you have not already generated layout for the design, and the Cells in Design list is incomplete or empty,

a.Type the first library and cell name in theCells in Design field, surrounded by double quotation marks:

"MYLib Mycell"

b.Select the >>> button to move the cell into the Components in Type list.

c.Repeat as needed.