Using Simulink

Blocks an Enabled Subsystem Can Contain

An enabled subsystem can contain any block, whether continuous or discrete. Discrete blocks in an enabled subsystem execute only when the subsystem executes, and only when their sample times are synchronized with the simulation sample time. Enabled subsystems and the model use a common clock.

Note    Enabled subsystems can contain GoTo blocks. However, only state ports can connect to GoTo blocks in an enabled subsystem. See the Simulink demo model, clutch, for an example of how to use GoTo blocks in an enabled subsystem.

For example, this system contains four discrete blocks and a control signal. The discrete blocks are:

• Block A, which has a sample time of 0.25 second
• Block B, which has a sample time of 0.5 second
• Block C, within the Enabled subsystem, which has a sample time of 0.125 second
• Block D, also within the Enabled subsystem, which has a sample time of 0.25 second

The enable control signal is generated by a Pulse Generator block, labeled Signal E, which changes from 0 to 1 at 0.375 second and returns to 0 at 0.875 second.

The chart below indicates when the discrete blocks execute.

Blocks A and B execute independent of the enable signal because they are not part of the enabled subsystem. When the enable signal becomes positive, blocks C and D execute at their assigned sample rates until the enable signal becomes zero again. Note that block C does not execute at 0.875 second when the enable signal changes to zero.

Creating an Enabled Subsystem

Triggered Subsystems