Masking Super Blocks

Apply a mask to hide the underlying blocks of a super block.

Masking is the main action from the Mask tool group. Masking hides the interior blocks of a super block and changes the super block to appear and act like a regular block. Additional tools let you edit, remove and restore a mask.
  1. From a diagram, select a super block:
  2. On the ribbon, from the Mask tool group , click the Auto Mask tool: .
    The super block is masked and behaves like a regular block. For example, double-clicking a block or a masked super block opens a block dialog for modifying parameters, whereas double-clicking an unmasked super block opens the diagram associated with the super block.
  3. Double-click the masked super block.
    For the masked super block named, Controller, which contains a diagram of a PID controller, the following block dialog appears with the parameters I, D and P:
    The values for these parameters are the input entries, I, D, and P, which are the context variables defined in the context of the root diagram of the Controller super block.

Navigating in Masked Super Blocks

You can navigate inside of a masked super block from the Project Browser or the context menu.

  • From the Project Browser, double-click a super block.
    The model display clears, and the main diagram of the super block appears.
    Note: Navigation from the Project Browser is the same for masked and unmasked super blocks.
  • From the modeling window, in a diagram, right-click a masked super block, and from the context menu, select Enter Masked Super Block.
    The model display clears, and the main diagram of the super block appears.
  • To clear the display of the super-block, in the blank space around the super block, double-click.
    The super block closes and the model display returns.

Editing Masked Super Blocks

The Edit Mask tool lets you modify the parameters associated with a super block.

  1. Select the masked super block you want to edit.
  2. On the ribbon, from the Mask tool group, click the Edit tool: .
    A dialog appears for you to modify the mask. Modifications can include adding or removing parameters or changing a parameter type or description.

Removing and Restoring Masks from Super Blocks

The Remove tool lets you remove a mask from a super block so that you can access the hidden contents of the super block. The Restore tool reapplies the mask.

  1. From a diagram, select a masked super block.
    The tools in the Mask tool group are activated.
  2. On the ribbon, from the Mask tool group, select the Remove tool: .
    The mask is removed from the super block and the diagrams and other information about the super block is accessible.
  3. Select the super block.
  4. From the ribbon, select the Restore tool: .
    A mask is reapplied to the super block and once again the super block behaves as a regular block.

Masking Examples

Learn about masking, auto-masking, and the creation of new blocks through masking.

Super Block Masking

A mask placed on a Super Block breaks the semi-global hierarchical scoping mechanism. A mask defines a set of parameters (mask parameters) and provides values for them, possibly as a function of parameters outside the Super Block. By analogy, an unmasked Super Block can be compared to an OML script and a masked Super Block, to an OML function.

Super Block Diagram

Consider the following diagram, inside a Super Block named SuperBlock:

If the Super Block Context is empty, the parameters of this diagram are A, B and dT. If the Super Block is masked, then the mask should define these three parameters. Such a mask may look as follows:

The mask parameter names are not directly visible on the mask GUI; they can be made visible by placing the cursor on top of the parameter description. In this case the mask parameters are named A, B and dT. The parameter values are defined by numerical values 1, 2 and 1.3. At this point the Super Block resembles a library block; the mask parameters are essentially local, private variables of the block, transparent to the user.


The mask for a Super Block may be created using the mask editor, or it can be generated automatically. The auto-masking facility identifies the set of parameters required to make the diagram inside the Super Block self-contained and use them both as mask parameter names and values. Auto-masking, applied to the previous example, creates the following mask:

This mask defines parameters named A, B and dT inside the Super Block from model parameters with the same names outside the Super Block. This mask can then be edited, in particular for providing descriptions for the parameters (auto-masking places by default the name of the parameter in the description field).

It should be emphasized that this model contains now two parameters named A, having the same value. The same is true for B and dT. Semantically, the presence of this mask is equivalent to placing the following instructions in the Context of the Super Block:

Creating New Blocks through Masking

Once a Super Block is masked, it can be used like a library block, and even placed in a block library. The values of the parameters should simply be replaced by default numerical values. Several Twin Activate base library blocks are masked Super Blocks.

Creating a New Block with a Digital Chebyshev Filter

Consider the creation of a new block that implements a digital Chebyshev filter of type I, based on the OML function cheby1. This function computes the numerator and the denominator of the discrete transfer function of the filter based on the order of the filter, its attenuation factor, and its cut-off frequency. The Chebyshev block does not exist in Twin Activate but the discrete transfer function does. So, a Chebyshev block can be constructed as a masked Super Block as follows:

The new block can now be created by auto-masking this Super Block, and editing the mask to provide a description for the block, and, descriptions and default values for the parameters:

This block can now be used as such in the model or be placed in a library for wider usage.