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State Writer

Write to a block state

  • State Writer block

Simulink / Signal Routing


The State Writer block sets the state of a supported state owner block.

State Writer blocks can write state to these state owner blocks:

  • Discrete State-Space

  • Discrete-Time Integrator

  • Delay

  • Unit Delay

  • Discrete Transfer Fcn

  • Discrete Filter

  • Discrete FIR Filter

  • Integrator

  • Second-Order Integrator

  • Outport of conditional subsystem blocks such as Enabled Subsystem, Triggered Subsystem, and Function-Call Subsystem

  • S-Function with multiple discrete states

    To configure an S-Function block as a state owner block, each data type work vector must be declared as a discrete state vector using ssSetDWorkUsedAsDState and named using ssSetDWorkName or ssSetDWorkRTWIdentifier in mdlInitializeSizes.


You can determine whether a block is a supported state owner block by the value of the block's IsStateOwnerBlock parameter. The expression

where blk is a block name or handle, returns 'on' if the block is a supported state owner block and 'off' otherwise.

To add a State Reader or State Writer block to your model, click on a state owner block to highlight it. Then, from the current block tab of the Simulink® toolstrip, click Reader-Writer. From the menu, select State Reader Block or State Writer Block.


The current block tab of the toolstrip might be labeled with the name of the highlighted block, for example, Outport, or it might be labeled Block, depending on the type of block you highlight.

Block tab of Simulink toolstrip, showing Reader-Writer button with drop-down menu beneath it. List items are State Reader Block and State Writer Block. A Unit Delay block is highlighted on the canvas.

If the state owner block has multiple states, then the State Reader or State Writer block dialog opens. Select a state from the State Owner Selector Tree.


Before adding a State Reader or State Writer block for a Second-Order Integrator block, you must explicitly name the states. See Specifying the State Names.

After you create a State Reader or State Writer block, a diamond shape with an x inside it badge appears above the state owner block, and the name of the state owner block appears next to the State Reader or State Writer block.

Simulink canvas showing Unit Delay block with a badge above it, and a State Writer block with "Unit Delay" appearing next to it

A State Reader or State Writer block cannot remain in the same system as its state owner block. After you create a State Reader or State Writer block, cut and paste it to move it to the desired location within the model hierarchy.

Alternatively, you can add a State Reader or State Writer block to your model from the Simulink Library Browser, then set the State owner block parameter from the block parameters dialog.


When you create a library block with a State Reader or State Writer block, you must also include the corresponding state owner block in the library block.

You can select a State Reader or State Writer 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 Related Blocks button 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.


The State Writer block does not support resettable states inside an Enabled Subsystem block. You must use a Reinitialize Function block to implement resettable states inside an Enabled Subsystem block. An external signal received at the enable port of the Enabled Subsystem triggers the execution of the Reinitialize Function block inside the subsystem. For more information on configuring Reinitialize Function block settings, see Reinitialize States of Blocks in Subsystem.

Example representing use of Reinitialize Function block inside Enabled subsystem to reset states.



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State value written to a state owner block.

When writing to a state owner block with an input scalar, the scalar value is expanded to match the dimension of the state. All elements of the state are set to the same value.

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


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Name of state owner block whose state this block is writing. To change the state owner block, select a block from the State Owner Selector Tree.


If the name of a state owner block contains a slash (/), the slash appears as two slashes (//) in the State Writer block parameters dialog. This notation distinguishes the slash in the block name itself from slashes that separate names at different levels of the model hierarchy.

Programmatic Use

Block Parameter: StateOwnerBlock
Type: character vector
Value: '' | '<model path/block name>'
Default: ''

Block Characteristics

Data Types

Boolean | bus | double | enumerated | fixed point | half | integer | single

Direct Feedthrough


Multidimensional Signals


Variable-Size Signals


Zero-Crossing Detection


Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

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