Simulink Function

Define a function using Simulink blocks

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Libraries:
Simulink / User-Defined Functions

Description

A Simulink Function block is a Subsystem block preconfigured to enable implementation of a function using Simulink^® blocks. To define and call a function using a Simulink Function block:

• Specify the function prototype, which includes the function name and input and output arguments, for example, y = f(u).

• Implement function behavior using blocks from the Simulink library.

• Configure your Simulink Function block to be called and reused anywhere in the model hierarchy.

When a function is called, the caller sends data through input arguments to the function, executes the function based on the implemented behavior, and then receives data back from the function through output arguments.

For more information, see Simulink Functions Overview.

Specify Function Prototype

The function prototype is separate from the implementation of the function. It specifies the input and output arguments and how the function should be called from other blocks in the model hierarchy. Each input or output argument specified in the function prototype is represented by an Argument Inport block or Argument Outport block, respectively. You can edit the function prototype by double-clicking the text displayed on the block.

Implement Function Behavior

To implement the desired behavior of your function, add any necessary Simulink blocks inside the subsystem. In addition to Argument Inport and Argument Outport blocks, a Simulink Function block can use Inport and Outport blocks to input and output data.

For an example, see Monitor Ink Status on Shared Printer Using Simulink Functions.

Configure Simulink Function Block

To configure a Simulink Function block, open the block parameters of the Trigger block located inside of the Simulink Function block.

• Function name – Specify the function name for the Simulink Function block.

• Function visibility – Select the scope visibility of the function.

  If Function visibility is set to port, you can also specify these parameters:

  • Execute function call asynchronously – Specify whether the function executes synchronously or asynchronously.

  • Scope to port – Specify the name of the exporting function port.

Call a Simulink Function

You can use a function caller and the function prototype to call and execute your function. A function defined in a Simulink Function block can be called from a Function Caller block, a Chart (Stateflow), a MATLAB Function block, a MATLAB System block, or an S-Function block.

For more information, see Call a Simulink Function from a Model.

Model Considerations

When using a Simulink Function block, consider whether your model requires persistence of states between functions calls or a continuous sample time.

• Persistence of state between function calls – If a Simulink Function block contains any blocks with state (for example, Unit Delay or Memory blocks), then their state values are persistent between calls to the function. If there are multiple calls to that function, the state values are also persistent between the calls originating from different callers.

• Unable to inherit continuous sample time – A Simulink Function block cannot inherit a continuous sample time.

Code Generation with Simulink Function 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

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

Model Service Access from Application Software Using Scoped Simulink Functions

Model services and accessing these services from a separate component.

• Open Live Script

Dynamic Priority Scheduling of Functions

A common modeling pattern to dynamically schedule the execution of functions using a Stateflow® chart.

• Open Model

Ports

Input

In — Signal input to a subsystem block

scalar | vector | matrix

Placing an Inport block in a subsystem block adds an external input port to the block. The port label matches the name of the Inport block.

Use Inport blocks to receive signals from the local environment.

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

ArgIn — Argument input to a subsystem block

scalar | vector | matrix

An Argument Inport block in a subsystem block provides an input port corresponding to an input argument. A port is not displayed on the subsystem block.

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

Output

Out — Signal output from a subsystem

scalar | vector | matrix

Placing an Outport block in a subsystem block adds an output port from the block. The port label on the subsystem block is the name of the Outport block.

Use Outport blocks to send signals to the local environment.

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

ArgOut — Argument output from a subsystem block

scalar | vector | matrix

An Argument Outport block in a subsystem block provides an output port corresponding to an output argument. A port is not displayed on the subsystem block.

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

Parameters

Main

Show port labels — Display options for port labels

FromPortIcon (default) | FromPortBlockName | SignalName | none

Select how to display port labels on the Subsystem block icon.

• none — Do not display port labels.

• FromPortIcon — If the corresponding port icon displays a signal name, display the signal name on the Subsystem block. Otherwise, display the port block name or the port number if the block name is a default name.

• FromPortBlockName — Display the name of the corresponding port block on the Subsystem block.

• SignalName — If the signal connected to the port is named, display the name of the signal on the Subsystem block. Otherwise, display the name of the corresponding port block.

For port label editing on Subsystem blocks, see Edit Port Labels on Subsystem Blocks.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	ShowPortLabels
Values:	'FromPortIcon' (default) | 'FromPortBlockName' | 'SignalName' | 'none'

Read/Write permissions — Levels of access to contents of subsystem

ReadWrite (default) | ReadOnly | NoReadOrWrite

Control user access to the contents of the subsystem.

• ReadWrite — Enable opening and modification of subsystem contents.

• ReadOnly — Enable opening but not modification of the subsystem. If the subsystem resides in a block library, you can create and open links to the subsystem and can make and modify local copies of the subsystem but cannot change the permissions or modify the contents of the original library instance.

• NoReadOrWrite — Disable opening or modification of subsystem. If the subsystem resides in a library, you can create links to the subsystem in a model but cannot open, modify, change permissions, or create local copies of the subsystem.

You do not receive a response if you attempt to view the contents of a subsystem whose Read/Write permissions parameter is set to NoReadOrWrite. For example, when double-clicking such a subsystem, the software does not open the subsystem and does not display any messages.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	Permissions
Values:	'ReadWrite' (default) | 'ReadOnly' | 'NoReadOrWrite'

Name of error callback function — Name of function to be called if error occurs

no default

Enter the name of a function to be called if an error occurs while the software executes the subsystem.

The software passes two arguments to the function: the handle of the subsystem and a character vector that specifies the error type. If no function is specified, the software displays a generic error message if executing the subsystem causes an error.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	ErrorFcn
Values:	'' (default) | function name in quotes
Data Types:	char | string

Permit hierarchical resolution — Resolution for workspace variable names

All (default) | ExplicitOnly | None

Select whether to resolve names of workspace variables referenced by this subsystem.

For more information, see Symbol Resolution and Symbol Resolution Process.

• All — Resolve all names of workspace variables used by this subsystem, including those used to specify block parameter values and Simulink data objects (for example, Simulink.Signal objects).

• ExplicitOnly — Resolve only names of workspace variables used to specify block parameter values, data store memory (where no block exists), signals, and states marked as “must resolve”.

• None — Do not resolve any workspace variable names.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	PermitHierarchicalResolution
Values:	'All' (default) | 'ExplicitOnly' | 'None'

Note

To configure the scope visibility and synchronicity of a Simulink Function block, open the block parameters of the Trigger block located inside of the Simulink Function block.

Block Characteristics

Data Types	Booleana | busa | doublea | enumerateda | fixed pointa | halfa | imagea | integera | singlea | stringa
Direct Feedthrough	no
Multidimensional Signals	yesa
Variable-Size Signals	no
Zero-Crossing Detection	no
a Actual data type or capability support depends on block implementation.

Extended Capabilities

C/C++ Code Generation

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

Actual code generation support depends on block implementation.

Fixed-Point Conversion

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

Actual data type support depends on block implementation.

Version History

Introduced in R2014b

R2024a: Define variant control variables of a Simulink Function block in the mask or model workspace

Starting in R2024a, you can define the variant control variables of a Simulink Function block with update diagram activation time in the mask or model workspace.

R2023b: Support nonunique function names when scoped to different ports

If scoped to different ports, function names of Simulink functions at the model root level do not have to be unique.

R2022b: Highlight related Function Caller blocks in referenced model

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

R2022a: Port-scoped Simulink Function blocks

A new port-scoped visibility option for the Simulink Function block is added for R2022a. To create a port-scoped Simulink Function block, set the Function visibility parameter of the Trigger block inside the Simulink Function block to port and enter the port name in the Scope to port field. Use port-scoped Simulink Function blocks to implement functions called through exporting function ports created by Function Element blocks. See Model Client and Server Components Using Function Ports.