Simulink®

Function-Call Subsystems

A function-call subsystem is a subsystem that another block can invoke directly during a simulation. It is analogous to a function in a procedural programming language. Invoking a function-call subsystem is equivalent to invoking the output methods (see Block Methods) of the blocks that the subsystem contains in sorted order (see How Simulink^® Determines the Sorted Order). The block that invokes a function-call subsystem is called the function-call initiator. Stateflow^®, Function-Call Generator, and S-function blocks can all serve as function-call initiators.

To create a function-call subsystem, drag a Function-Call Subsystem block from the Ports & Subsystems library into your model and connect a function-call initiator to the function-call port displayed on top of the subsystem. You can also create a function-call subsystem from scratch by first creating a Subsystem block in your model and then creating a Trigger block in the subsystem and setting the Trigger block's Trigger type to function-call.

You can configure a function-call subsystem to be triggered (the default) or periodic by setting the Sample time type of its Trigger port to be triggered or periodic, respectively. A function-call initiator can invoke a triggered function-call subsystem zero, once, or multiple times per time step. The sample times of all the blocks in a triggered function-call subsystem must be set to inherited (-1).

A function-call initiator can invoke a periodic function-call subsystem only once per time step and must invoke the subsystem periodically. If the initiator invokes a periodic function-call subsystem aperiodically, the simulation is halted and an error message displayed. The blocks in a periodic function-call subsystem can specify a noninherited sample time or inherited (-1) sample time. All blocks that specify a noninherited sample time must specify the sample time, i.e., if one block specifies .1 as its sample time all other blocks must specify a sample time of .1 or -1. If a function-call initiator invokes a periodic function-call subsystem at a rate that differs from the sample time specified by the blocks in the subsystem, the simulation is halted and an error message is displayed.

For more information about function-call subsystems, see Function-Call Subsystems.

Triggered and Enabled Subsystems

Conditional Execution Behavior