Function Caller

Call a Simulink function

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Libraries:
Simulink / User-Defined Functions

Description

A Function Caller block calls and executes a Simulink^® function. Simulink functions specify a function prototype which includes the function name and input and output arguments. For example, when a Function Caller block calls a function with prototype y = f(u), the input of the Function Caller block is the input argument, u, of the Simulink function and the output argument, y, of the Simulink function is the output of the Function Caller block.

In this example, a Function Caller block is configured to call and execute the Simulink function, y = timestwo(x), defined in a Simulink Function block. To test the function call, a Sine Wave block is connected to the input port x to provide input data and a Scope block is connected to the output port y to view results from the output.

You can call a Simulink function defined in a Simulink Function block, Stateflow^® Chart (Stateflow) as an exported function, or an S-Function block. For more information on defining a Simulink function, see Define a Simulink Function in a Model.

For more information, see Simulink Functions Overview.

Tip

You can use a Function Caller block to call a function outside of the model hierarchy.

For more information, see Simulink Function Blocks in Referenced Models.

Code Generation with Simulink Function and Function Caller Blocks

If you have Simulink Coder™ or Embedded Coder^®, you can generate code from models containing Simulink functions. For more information, see Simulink Function Blocks and Code Generation (Embedded Coder) and Configure Entry-Point Function Interfaces for Simulink Function and Function Caller Blocks (Embedded Coder).

Examples

Reuse Multiple Instances of a Simulink Function

To reuse components, use multiple instances of a function.

• Open Live Script

Monitor Ink Status on Shared Printer Using Simulink Functions

How multiple clients can send requests to a server and receive a status from the server. Using Simulink® functions, different subsystems can call functions from other subsystems and interact in Simulink and Stateflow®. In this example, you model the ink status monitoring of a shared printer using Simulink functions.

• Open Live Script

Temperature Control System Communicating with Messages

Distributed control of room temperatures by processing messages from room thermostats and communicating control commands using messages to different receivers.

• Open Model

Ports

Input

Input argument — Input signal for input argument

scalar | vector | matrix

Input signal for an input argument that is sent to the function.

The function prototype determines the number and name of input ports that appear on the Function Caller block. Connect signal lines to the input ports to send data to a function through the function input arguments.

For example, y = myfunction(u) creates one input port (u) on the Function Caller block.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Output

Output argument — Output signal or message for output argument

scalar | vector | matrix | message

Output signal for an output argument that the function returns.

The function prototype determines the number and name of output ports that appear on the Function Caller block. Connect signal or message lines to the output ports to receive data from a function through the function output arguments. The Function Caller block outputs messages when you select the Execute function call asynchronously check box.

For example, y = myfunction(u) creates one output port (y) on the Function Caller block.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Parameters

Function prototype — Specify function prototype

y=f(u) (default) | character vector | string

Specify the function prototype between a Function Caller block and a Simulink function.

Note

To call a function defined in a Simulink Function block:

• Function call argument names must match the function arguments.

• Function names, input arguments, and output arguments must be valid MATLAB^® identifiers.

Programmatic Use

Block Parameter: FunctionPrototype

Type: character vector

Values: 'y=f(u)' | function prototype

Default: 'y=f(u)'

Function name — Qualified function name

f (default) | character vector | string

Qualified function name, specified as a character vector or string.

The function name is shown on the block icon. You can edit the name by clicking on the parameter value on the block icon and entering a new value.

Note

This parameter is automatically synchronized with the Function prototype parameter of the Function Caller block.

For more information about resolving a function through qualification, see Scoped Simulink Function Blocks in Models and Scoped Simulink Function Blocks in Subsystems.

Programmatic Use

Block Parameter: ScopedFunctionName

Type: character vector

Values: 'f' | 'Client.f' | function name

Default: 'f'

Input argument specifications — Specify input argument data type, dimensions, and complexity

<Enter example> (default) | MATLAB expression

Specify a comma-separated list of MATLAB expressions that combine data type, dimensions, and complexity (real or imaginary) for each input argument. For examples, see Argument Specification for Simulink Function Blocks.

Note

This specification must match the Simulink Function block data type specified with the Data type parameter of the Argument Inport block.

Programmatic Use

Block Parameter: InputArgumentSpecifications

Type: character vector

Values: '' | MATLAB expression

Default: ''

Output argument specifications — Specify output argument data type, dimensions, and complexity

<Enter example> (default) | MATLAB expression

Specify a comma-separated list of MATLAB expressions that combine data type, dimensions, and complexity (real or imaginary) for each output argument. For examples, see Argument Specification for Simulink Function Blocks.

Note

This specification must match the Simulink Function block data type specified with the Data type parameter of the Argument Outport block.

Programmatic Use

Block Parameter: OutputArgumentSpecifications

Type: character vector

Values: '' | MATLAB expression

Default: ''

Sample time — Time interval between function calls

-1 (default) | scalar | vector

Specify the interval of time between calls to the Simulink function.

By default, the block inherits its sample time based on the context of the block in the model. To set a different sample time, enter a value using a sample time format from the table in Specify Sample Time.

If the Function Caller block has any inputs, it is a nonsource block, and you must set the sample time to -1.

Programmatic Use

Block Parameter: SampleTime

Type: string | character vector

Values: scalar | vector | sample time

Default: '-1'

Execute function call asynchronously — Option to execute function calls asynchronously

off (default) | on

Specify whether to execute the Simulink Function block associated with this Function Caller block asynchronously.

• Select Execute function call asynchronously to enable asynchronous execution.

  Asynchronous execution is when the caller invokes a function, the function executes based on the priority order, and returns the output arguments to the caller. The function executes based on the ordering defined in the Schedule Editor and then returns the output arguments to the caller. The block outputs these arguments using a message output port.

  • If there is one function output argument, the output argument becomes the message payload.

  • If there is more than one function output argument, the Function Caller block bundles the output arguments as a structure that becomes the message payload.

  Connect the message output port to a Message Triggered Subsystem block in immediate mode. The Message Triggered Subsystem block acts as a callback for the function.

• Clear Execute function call asynchronously to enable synchronous execution.

  Synchronous execution is when the caller invokes a function, the function runs immediately, and returns the output arguments to the caller.

Programmatic Use

Block Parameter: AsynchronousCaller

Type: character vector

Values: 'on' | 'off'

Default: 'off'

Block Characteristics

Data Types	Boolean | bus | double | enumerated | fixed point | integer | single
Direct Feedthrough	yes
Multidimensional Signals	yes
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

To generate code for a model that uses the Function Caller block to call and execute a Simulink function asynchronously:

• Select the Execute function call asynchronously parameter in the Function Caller block parameters.

• Set the System target file parameter in Configuration Parameters. For more information, see Configure a System Target File (Embedded Coder).

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced in R2014b

R2025a: Edit qualified function name from Function Caller block

Starting in R2025a, the Function Caller block supports editing the qualified function name with the Function name parameter. Use one of these methods.

• Use set_param to set ScopedFunctionName block parameter.

• Click on the parameter value on the block icon and enter a new value.

  

R2022b: Highlight related Simulink Function blocks in referenced model

Starting in R2022b, when you select a Function Caller block whose related Simulink Function block is in a referenced model, both the Simulink Function block and the Model block of the referenced model are highlighted.

R2022b: Specify asynchronous function execution

Starting in R2022b, you can specify a Simulink function to be executed asynchronously by selecting the new Execute function call asynchronously parameter in the Trigger block inside of the Simulink Function block and in the Function Caller block.