Initialize Function

Execute subsystem on model initialize event

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Libraries:
Simulink / User-Defined Functions

Description

The Initialize Function block is a preconfigured Subsystem block that executes on a model initialize event. By default, the Initialize Function block includes:

• An Event Listener block with the Event type set to Initialize

• A Constant block with the Constant value set to 0

• A State Writer block with no State owner block set

Use this block when you need to initialize a task based on an event. For example, Initialize Function block inside a Simulink model referenced by a Model block is triggered when the Model block receives a function-call control signal at its initialize port. For more information about the modeling patterns using Initialize Function block, see Common Uses of the Initialize Function Block. This block allows you to schedule and control the initialization of a task in a model.

Customize the contents of the Initialize Function block by, for example, replacing the Constant block with source blocks that generate the state value for the State Writer block and specifying a State owner block for the State Writer block.

Conditionally executed subsystems with output ports are fully supported within Initialize Function blocks. For a list of unsupported blocks and features, see Initialize, Reinitialize, Reset, and Terminate Function Limitations.

The input and output ports of a component containing Initialize Function and Terminate Function blocks must connect to Inport and Outport blocks, respectively.

The code generated from this block is part of the model_initialize function that is called once at the beginning of model execution.

You can select an Initialize Function, Reinitialize Function, Reset Function, or Terminate Function block or a corresponding state owner block to highlight blocks related to it. To show a related block in an open diagram or new tab, pause on the ellipsis that appears after selection. Then, select Related Blocks from the action bar. When multiple blocks correspond to the selected block, a list of related blocks opens. You can filter the list of related blocks by entering a search term in the text box. After you select a related block from the list, window focus goes to the open diagram or new tab that shows the related block.

Examples

Initialize, Reset, and Terminate State of Simulink Block

Use the Initialize Function, Reset Function, and Terminate Function blocks to respond to events in a Simulink model.

• Open Model

Reading and Writing States with the Initialize Function and Terminate Function Blocks

In this example, the Initialize Function block uses the State Writer block to set the initial condition of a Discrete Integrator block to 10.

• Open Model

Common Uses of the Initialize Function Block

Use the Initialize Function block to perform these common initialization actions.

• Open Live Script

Block Characteristics

Data Types	Booleana | busa | doublea | enumerateda | fixed pointa | halfa | 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

R2025a: Variant control variables in mask and model workspaces supported

You can define variant control variables in the mask or model workspaces to control active variants in the Initialize Function block, provided the Generate preprocessor conditionals parameter is off.