Virtuoso Layout Editor User Guide -- 6. The Layer Selection Window (LSW)

Virtuoso Layout Editor User Guide, Product Version 5.0

6

The Layer Selection Window (LSW)

This chapter contains these topics:

About the Layer Selection Window

Choosing the Current Entry Layer

Setting How Layers Appear

About the Layer Selection Window

The Layer Selection Window (LSW) lets you choose the design layer for each shape you create, make design layers visible or invisible, or make instances and pins selectable or unselectable.

The default location of the LSW is the upper left side of the screen. You can change the size and location of the LSW by using leSetLSWBBox().

Edit Menu

The Edit menu lets you set, change, save, or load layer settings.

The Set Valid Layers command lets you choose which layers appear in the LSW.

Note: If you are using the leLswLayers subclass of the leRules class of the technology file, only the layers listed there appear in the Set Valid Layer form.

The Tap command lets you click on an object to set the current layer. When the environment variable layerTapCycle is set to t, clicking repeatedly cycles through all the layers under the cursor.

The Load command adds previously saved layers to the LSW.

The Save command writes your current LSW layer attributes to an ASCII file or to a technology file in virtual memory. If you want to make these attributes permanent, you must use the Save Technology File form (from the Command Interpreter Window, choose Tools - Technology File Manager).

The Option command lets you show the full name of the layer-purpose.

The Display Resource Editor command lets you change how layers appear.

Current Entry Layer

The current entry field shows the current layer for all shape creation commands.

Technology File

The technology file field shows the name of the technology file that you are using.

Inst Button

The Inst toggle button turns cell instances selectable (on) or unselectable (off).

Pin Button

The Pin toggle button turns pin instances used by Cadence^® routing tools selectable (on) or unselectable (off). To select pins on a current layer, see Searching for Shapes and Pins on One Layer.

AV and NV Buttons

The AV button turns all layers visible.

The NV button turns all layers invisible in the layout window. This can cause the design to redraw faster. Invisible layers are not selectable in the LSW.

To see the result, choose Window - Redraw.

AS and NS Buttons

The AS button turns all layers selectable.

The NS button turns all layers unselectable. When a layer is unselectable, it cannot be selected in the layout window. You can make a complex, dense design easier to edit by making fewer layers selectable. This helps you avoid editing objects on the wrong layer.

Layers and Mouse Functions

The LSW lists all the valid layer-purpose pairs defined in the technology file. The layer-purpose pairs are sorted by display priority. If the leLswLayers rule is defined in the technology file, then only the valid leLswLayers layers are listed. In that case, the layer-purpose pairs are listed in the same order as they are defined in the leLswLayers rule.

Click with one of the mouse buttons on a layer name to do any of the following:

To set the current (entry) layer, click.

To change layer appearance, press Shift and click.

To toggle a layer between visible and invisible, click middle.

To make all layers but one invisible, press Shift and click middle.

To toggle a layer between selectable and unselectable, click right.

To make all layers but one unselectable, press Shift and click right.

You can specify the order of the layers in the LSW by editing the leLswLayers class of the technology file. You can specify the layer abbreviation name by editing the techLayers class of the technology file.

Scroll Bar

Use the scroll bar to move up and down in the list of layers.

To move down in the list of layers, click on the bottom arrow.

To move up in the list of layers, click on the top arrow.

Choosing the Current Entry Layer

The layer shown at the top of the LSW is the current entry layer. You create objects on layers such as metal or via, which correspond to a layer for your physical design. You choose the entry layer with the LSW, which shows all the layers in your library that are valid.

      To choose an entry layer, click on the layer in the LSW.

The name of the layer appears at the top of the LSW.

Choosing the Entry Layer from an Object

The Tap command lets you click on an object to set the entry layer. This is useful if you want to create objects on the same layer as some other object in your design.

You can have the layer tap command behave in one of two ways by setting the environment variable layerTapCycle to either t or nil.

When set to nil, the default, the system selects the layer of the object you tap on whose edge is closest to or coincident with the cursor.

When t, you can cycle through the layers of overlapping objects by tapping repeatedly without moving the cursor until the layer you want is displayed.

To see which layer is currently the entry layer, look at the Layer Selection Window.

Using Tap For Layer Selection

To change entry layers using the Tap command,

In the LSW, choose Edit - Tap [t].

Click left on an object. If objects are overlapped, continue to click until you select the layer you want.

The layer of the object becomes the current layer.

Note: If the object is drawn on a layer that is not in the LSW, the current entry layer is not changed.

You can use the bindkey t to start the Tap command in a layout window even though the bindkey is not listed in the LSW Edit menu. (It is not listed in the LSW Edit menu because it affects only layout windows, not the LSW.)

Changing the Available Entry Layers

The LSW lists all the valid layer-purpose pairs defined in the technology file. The layer-purpose pairs are sorted by display priority. If the leLswLayers rules are defined in the technology file, only the valid leLswLayers layers are listed. In that case, the layer-purpose pairs are listed in the same order as they are defined in the leLswLayers rule.

Note: If you are using the leLswLayers subclass of the leRules class of the technology file, only the layers listed there appear in the Set Valid Layer form.

The Set Valid Layer form is used to specify which layers are valid and therefore displayed in the LSW. The Set Valid Layer form displays all layer-purpose pairs in the technology file. However, if the leLswLayers rule is defined in the technology file, only the leLswLayers layers will be displayed in the Set Valid Layer form.

About the Set Valid Layer Form

Tech File Name displays the technology file being used for the current cellview.

Tech Library Name is the name of the library that contains the technology file.

All Valid makes all the layer-purpose pairs valid, making them appear in the LSW.

None Valid makes all layer-purpose pairs not valid, removing them from the LSW, except the current entry layer.

Layers lists all the layer-purpose pairs defined in the technology file. If the leLswLayers rule is defined in the technology file, only the leLswLayers layers are listed. The box to the right of the layer-purpose pair icon indicates whether or not the layer is valid. If the box is filled, the layer is valid and is displayed in the LSW. If the box is empty, the layer is marked invalid and is not displayed in the LSW.

Setting Valid Layers

To add or remove layers from the LSW (making them valid or not valid),

From the LSW, choose Edit - Set Valid Layers.

The Set Valid Layer form appears.

Do any of the following:

To add a layer to the LSW, click on the box to the right of the layer name so it is filled in.

To remove a layer from the LSW, click on the box to the right of the layer name so it is empty.

To add all layers to the LSW, click All Valid.

To remove all layers except one layer (the current layer) from the LSW, click None Valid.

Note: Even though you click None Valid, one layer will always be valid in the LSW.

Click OK.

Your changes are stored in the LSW database.

To save your changes to a file, use the Save form. To save your changes to the technology file, first use the Save form to save the changes to memory, then use the Save Technology File form (from the Command Interpreter Window, choose Tools - Technology File Manager) to write the technology file to disk.

You might want to use different sets of drawing layers to edit different types of cells in a library. The Save command saves the current set of drawing layers shown in the LSW to a file or to the technology file. Later you can load layers from the file or technology file.

Note: If you are using the leLswLayers subclass of the leRules class of the technology file, only the layers listed there appear in the Set Valid Layer form.

Using the Save Form

The Save form writes your current LSW layer attributes to an ASCII file or to a technology file in virtual memory.

If you want to make these attributes permanent, you must use the Save Technology File form (from the Command Interpreter Window, choose Tools - Technology File Manager).

About the Save (Valid Layers) Form

Save To lets you save all layers' validity, visibility, and selectability attributes to either a technology file or an ASCII file.

Techfile saves all layers listed in the LSW as valid layers in the technology file used for this library.

File saves all layers in the LSW to a file that you can later load with the
Edit - Load command in the LSW.

Saving a Set of Entry Layers

To save layers,

From the LSW, choose Edit - Save.

The Save form appears.

Do one of the following:

To save to a file, choose File and type the name of the file. Include a path if you want to save the file outside your current directory.

To save to the technology file (shown at the top of the LSW) in memory, choose Techfile.

Click OK.

The LSW's current validity, visibility, and selectability attributes are written to the specified file or technology file in virtual memory. If you want to make these attributes permanent, you must use the Save Technology File form (from the Command Interpreter Window, choose Tools - Technology File Manager).

Using the Load Form

The Load form lets you change the LSW validity, visibility, and selectability attributes from a saved file or the technology file in virtual memory. Because the LSW displays only valid layers, the Load command can change which layer-purpose pairs are displayed in the LSW. Loading from a file can be used to restore a predefined set of valid, visible, and selectable layer-purpose pairs. Loading from the technology file can be used to restore the default validity, visibility, and selectability attributes.

About the Load (Valid Layers) Form

Load From loads layers defined in either a technology file or an ASCII file.

Techfile loads all layers defined as valid drawing layers in the technology file used for this library.

File loads layers you previously saved to a file using the Edit - Save command in the LSW.

Loading Layers from a File

To load a set of layers you saved,

From the LSW, choose Edit - Load.

The Load form appears.

Choose File and type the name of the file you want to load.

Include a path if you want to load a file stored outside your current directory.

Click OK.

The list of layers in the LSW changes.

Setting How Layers Appear

Changing Layer Appearance

The layers and how they appear on the screen and in your plots are defined by the technology file and the display.drf file.

The technology file defines the layer-purpose pairs. This includes the layer name, purpose name, display priority, display packet, and layer rules.

      To change a layer definition in the technology file, use the Edit Layers form.

Note: Changing the technology file affects all libraries that use that technology file.

The display.drf file defines the display resources including colors, stipples, line styles, and packets. Each packet is a named combination of stipple, line style, fill color, and outline color. Packets are associated with one or more layer-purpose pairs in the technology file.

      To change a layer definition in the display.drf file, use the Display Resource Editor.

Making One Layer Visible or Invisible

To reduce the amount of detail in the cellview, you can make some layers invisible.

To make a layer invisible,

In the LSW, click middle on the layer.

Choose Window - Redraw to see the result.

Repeat steps 1 and 2 if you want to make the layer visible again.

Making All Layers Visible or Invisible

To make all layers except the current entry layer invisible,

Click NV (not visible) at the top of the LSW.

Choose Window - Redraw to see the result.

Click AV (all visible) at the top of the LSW to make all layers visible again.

Choose Window - Redraw to see the result.

You cannot make the current drawing layer, shown at the top of the LSW, invisible.

Note: If you are using the leLswLayers subclass of the leRules class of the technology file, only the layers listed there appear in the Set Valid Layer form.

Making All but One Layer Invisible

To make only one layer visible,

In the LSW, press Shift and click middle on the layer you want to be the only visible layer.

All other layers are shaded to show that they are invisible and unselectable.

Choose Window - Redraw to see the result of your changes.

Making the Layer-Purpose Full Name Not Appear

The LSW displays only the first seven characters of the layer-purpose name until you roll the cursor over the layer-purpose displayed on the LSW. The full name is displayed in a pop-up window. You can set an LSW option to make the full layer-purpose name not appear when the cursor is positioned over the layer-purpose.

To make the layer-purpose full name not appear,

From the LSW, choose Edit-Option.

The LSW Option form appears.

Click on the Show layer-purpose full name command button to turn it to off.

Click OK.

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