Blanket Directives in Schematic Documents

The Blanket Directive is a powerful feature in Altium Designer's Schematic Editing domain. It 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.

Access

Blankets can be placed on schematic documents (*.SchDoc), by choosing Place » Directives » Blanket  [P, V, L] from the editor's main menus.

Placement

To place a purely 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.

While placing a blanket:

• 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.
• Press the Tab key to access the Blanket dialog, from where properties for the blanket can be changed on-the-fly.

Editing

The properties of a blanket object can be modified before, during and after placement. Editing itself falls into two categories – graphical and non-graphical. The following sections detail the various methods of editing.

Editing via Blanket Dialog

This method of editing uses the following dialog to modify the properties of a blanket object:

The Blanket dialog can be accessed:

• Prior to entering placement mode, from the Schematic – Default Primitives page of the Preferences dialog. This allows you to change the default properties for the blanket object, which will be applied when placing subsequent blankets.
• During placement, by pressing the Tab key.
• After placement, by:
  
  • Double-clicking on the blanket's outline.
  • Right-clicking over the blanket's outline and choosing the Properties command from the context menu.
  • Selecting the Edit » Change command, then clicking once over the blanket's outline.

Use the controls available to configure the blanket as required.

Appearance

Properties that can be modified include:

• Fill Color
• Border Color
• Border Width – set to Smallest, Small (default), Medium, or Large.
• Line Style – set to either Solid, Dashed (default), or Dotted.

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.

Editing via Inspector and List Panels

As with all other design objects, blanket objects can be inspected and their properties modified, through the editor's SCH Inspector and SCH List panels. When used in conjunction with appropriate filtering (using the SCH Filter panel) they enable the designer to display just those objects falling under the scope of the active filter – allowing the targeting and editing of multiple design objects with greater accuracy and efficiency.

Filtering

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.

Editing Graphically

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:

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 anti-clockwise and in steps of 90°.
• Press the X or Y keys to flip the blanket along the X-axis or Y-axis respectively.