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Virtual Blocks

When creating models, you need to be aware that Simulink blocks fall into two basic categories: nonvirtual and virtual blocks. Nonvirtual blocks play an active role in the simulation of a system. If you add or remove a nonvirtual block, you change the model's behavior. Virtual blocks, by contrast, play no active role in the simulation. They simply help to organize a model graphically. Some Simulink blocks can be virtual in some circumstances and nonvirtual in others. Such blocks are called conditionally virtual blocks. The following table lists Simulink's virtual and conditionally virtual blocks.

Table 3-1: Virtual Blocks 
Block Name
 Condition Under Which Block Will Be Virtual
Bus Selector
Always virtual.
Data Store Memory
 Always virtual.
Demux
 Always virtual.
Enable Port
 Always virtual.
From
 Always virtual.
Goto
 Always virtual.
Goto Tag Visibility
 Always virtual.
Ground
 Always virtual.
Inport
 Always virtual unless the block resides in a conditionally executed subsystem and has a direct connection to an outport block.
Mux
 Always virtual.
Outport
 Virtual if the block resides within any subsystem block (conditional or not), and does not reside in the root (top-level) Simulink window.
Selector
 Always virtual.
Subsystem
 Virtual if the block is not conditionally executed.
Terminator
 Always virtual.
Test Point
 Always virtual.
Trigger Port
 Virtual if the outport port is not present.


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