Working with a Blanket Object on a Schematic Sheet in Altium Designer

Parent page: Schematic Objects

 
Two placed blankets - a simple rectangular shape blanket on the left and a polygon blanket on the right.

Summary

A blanket directive enables other parameter set-based directives to quickly be applied to a group of nets simply by covering those nets with a 'blanket'. When placing a blanket, you can either define a simple rectangular shape or a polygonal-shape. The latter gives more precise control over coverage of the required net objects on a sheet.

The blanket applies to all nets that:

• are completely within the area defined by the blanket, or
• have at least one end vertex of the wire / bus / harness under the blanket, or
• have a net label attached to the wire / bus / harness, and that net label is under the blanket.

Availability

Blankets are available for placement in the schematic editor only. To place a blanket:

• Click Place » Directives » Blanket from the main menus.
• Right-click in the schematic editor, then click Place » Directives » Blanket.

Placement

To place a rectangular blanket:

1. Launch the command using the access method listed previously.
2. Position the cursor and click or press Enter to effect placement of the top-left corner.
3. Position the cursor and click or press Enter to effect placement of the bottom-right corner.
4. Right-click or press Enter to complete placement.
5. Continue placing further blankets, or right-click or press Esc to exit placement mode.

To place a polygonal-shaped blanket:

1. Launch the command using the access method listed previously.
2. Position the cursor and click or press Enter to anchor the starting point for the blanket.
3. Position the cursor and click or press Enter to anchor a series of segments that define the shape of the blanket.
4. After placing the final segment, right-click or press Esc to complete placement. There is no need to 'close' the polygon as the software will automatically complete the shape by adding required segments to connecting the start point to the final segment placed.
5. Continue placing further blankets, or right-click or press Esc to exit placement mode.

Additional actions that can be performed during placement while the blanket is still floating on the cursor are:

• Press the Tab key to access an associated properties dialog, from where properties for the arc can be changed on-the-fly.
• Press the Spacebar to change the segment direction mode between horizontal and vertical.
• Press Backspace to delete the previously committed segment when defining a polygonal shape for the blanket. Successive use of Backspace will delete previous segments in order.

Graphical Editing

This method of editing allows you to select a placed blanket object directly in the workspace and change its size, shape, or location graphically. When a blanket object is selected, the following editing handles are available:

Example of selected polygonal (left) and rectangular (right) blankets.

Click and drag an editing handle at the center of an edge to move that edge of the blanket.

For a rectangular blanket, click and drag a corner editing handle to resize in both vertical and horizontal planes simultaneously.

Click anywhere on the outline of the blanket – away from editing handles – and drag to reposition it. The blanket can be rotated or flipped while dragging:

• Press the Spacebar to rotate the blanket. Rotation is counterclockwise and in increments of 90°.
• Press the X or Y keys to flip the blanket along the X-axis or Y-axis.

Non-Graphical Editing

The following methods of non-graphical editing are available:

Via an Associated Properties Dialog

Dialog page: Blanket

This method of editing uses the Blanket dialog to modify the properties of a blanket object.

The Blanket dialog

The Blanket dialog can be accessed prior to entering placement mode, from the Schematic – Default Primitives page of the Preferences dialog. This allows the default properties for the blanket object to be changed, which will be applied when placing subsequent blankets.

During placement, the dialog can be accessed by pressing the Tab key.

After placement, the dialog can be accessed in one of the following ways:

• Double-click on the placed blanket object.
• Place the cursor over the blanket object then right-click and choose Properties from the context menu.
• Click Edit » Change from the main menus then click once over the placed blanket object.

Via an Inspector Panel

Panel pages: SCH Inspector, SCH Filter

An Inspector panel enables the designer to interrogate and edit the properties of one or more design objects in the active document. Used in conjunction with appropriate filtering - by using the applicable Filter panel, or the Find Similar Objects dialog - the panel can be used to make changes to multiple objects of the same kind, from one convenient location.

Via a List Panel

Panel pages: SCH List, SCH Filter

A List panel allows the designer to display design objects from one or more documents in tabular format, enabling quick inspection and modification of object attributes. Used in conjunction with appropriate filtering - by using the applicable Filter panel, or the Find Similar Objects dialog - it enables the display of just those objects falling under the scope of the active filter – allowing the designer to target and edit multiple design objects with greater accuracy and efficiency.

Filtering Support

In support of the blanket object, two particularly useful keywords are available for use when targeting blankets using logical query expressions. These complement the range of other keywords used to target a blanket based on its properties.

• Collapsed - the object is collapsed (also useful when targeting Compile Masks). This keyword can be found in the SCH Functions - Fields category, when using the Query Helper.
• IsBlanket - is the object a blanket? This keyword can be found in the SCH Functions - Object Type Checks category, when using the Query Helper.

Create logical expressions for queries to target and return blankets in your design as required. Some examples of logical query expressions targeting blankets are:

IsBlanket And Collapsed - targets all blanket objects that are currently collapsed.

IsBlanket And Not Collapsed - targets all blanket objects that are currently not collapsed.

Disabling a Blanket

Once placed, blankets can be temporarily disabled by clicking on the small triangle in the upper left. Click once to disable the blanket; click again to re-enable it. This provides a convenient way of controlling the impact of the blanket without needing to remove it completely from the design.

Identifying the Nets that the Blanket Applies to

In the animation below, the blanket has been placed to cover a number of nets that need to be defined as differential pairs. To check which nets the blanket will apply to, use the Underline Connections feature to highlight them, as shown. Click the  button to remove the highlighting.

The nets covered by the blanket can be targeted by a parameter set object placed so that it touches the blanket.