Preserve Existing Chains

Ensures that any existing chains in the design are not broken during interactive chaining.

Environment variable: chainPreserveExistingChains

Use Device Order

Maintains the relative horizontal starting positions of the specified instances when forming the chain.

Instances are sorted by the x-coordinates of their origins (from lowest to highest) and the resultant list used to abut the devices from right to left. This argument does not always preserve device orientations; for example, it may be necessary to mirror an instance to abut it with its neighbor.

If Use Device Order is selected, abutment is supported for instances that have different values set for the abutClass property but have their abutClass values defined as equivalent. Dummy, unconnected, and part-connected devices are chained, where possible. The device nets are assigned to enable device abutment in the order defined by Use Device Order.

If Use Device Order is deselected, these equivalentAbutClasses are ignored. Dummy and unconnected devices are not chained. These devices are placed down separately in the order: chains, dummies, and then unconnected devices. Part-connected devices are chained, where possible, with nets assigned to enable device abutment.

If Use Device Order is selected, advanced node devices are chained even if their S/D pins are on different nets. In this case, the devices are abutted on dummy pins.

Environment variable: chainUseDeviceOrder

Extend Selection

Always selects the entire chain when you click an individual instance, mfactored device, or folded device within the chain. When switched off, you can selected individual devices, mfactors, or folded legs within a chain without selecting the entire chain.

Environment variable: chainExtendSelection

Interdigitate Chains

Automatically identifies nodes that qualify as pseudoparallel connections and defines them during chaining and abutment. A pseudoparallel net connects nodes that are always the same voltage, so current does not pass through the net.

Environment variable: lxAllowPseudoParallelNets

Mirror

Automatically mirrors the instances in a chain.

Environment variables: chainMirror, chainPermutePins

Permute

Automatically permutes the instances in a chain.

Environment variables: chainPermute, chainPermutePins

Create In Place

Creates the device chains on layout canvas at the same location as the left-most instance in a row region, if at least one of the instances selected for chaining is on a row region. If none of the selected instances are on a row region, the chain is created at the same location as the left-most selected instance.

If the original instance is at an orientation, such as R90, that can place the chain vertically, the Create In Place option can be used to create the new chain above or below the original instance.

Choose between Increasing or Decreasing to specify how the new chain is positioned.

Environment variables: chainInPlace, chainInPlaceDirection

Align PMOS

Controls the alignment of PMOS chains. The default alignment for PMOS chains is Top but you can choose to align a chain to Center or Bottom.

Environment variable: lxChainAlignPMOS

If you are using a FinFET design, the option name will be displayed as Align PFIN, which can be used to control the alignment of PFIN device chains.

Depending on the PDK that you are using, the abutment function being used might trigger a different alignment compared to the alignment that you specify. In this case, the user-defined alignment is disregarded and a message indicating the same is issued.

Align NMOS

Controls the alignment of NMOS chains. The default alignment for NMOS chains is Bottom but you can choose to align a chain to Top or Center.

Environment variable: lxChainAlignNMOS

If you are using a FinFET design, the option name will be displayed as Align NFIN, which can be used to control the alignment of NFIN device chains.

Depending on the PDK that you are using, the abutment function being used might trigger a different alignment compared to the alignment that you specify. In this case, the user-defined alignment is disregarded and a message indicating the same is issued.

Show Device List

Expands the form to list the transistors available for chaining. If there is nothing preselected in the layout canvas, the form lists all the transistors in the design. If there were transistors selected in the layout canvas before you choose the Generate Chained Devices command, only the selected transistors are listed as highlighted. Select the transistors to chain from the list and click Apply to chain them.