Parameter Writer

Write to block parameter or variable

• 

Libraries:
Simulink / Signal Routing

Description

The Parameter Writer block changes block parameter values by writing to one of the following:

• A parameter of a block that is tunable during simulation

• An instance parameter that belongs to a Model block that references a model

• A masked subsystem parameter

• A model workspace variable

• A base workspace variable

• A variable created in Simulink.data.Dictionary

A block with a parameter that can be written by a Parameter Writer block is called a parameter owner block. For the Parameter Writer block to find the supported parameters of a parameter owner block, the supported parameters must be enabled.

Use the Parameter Writer block with the Initialize Function, Reinitialize Function, and Reset Function blocks to respond to events. For example, an event could be reading the value from a hardware sensor and then updating a block parameter based on the sensor value. For more information about using the Parameter Writer block, see Initialize and Reset Parameter Values.

For a Parameter Writer block in a masked subsystem, the Parameter Writer block and corresponding parameter owner block must have the same immediate parent masked subsystem.

Otherwise, a Parameter Writer block must be in the same mask as either:

• The block whose parameter is directly written by the Parameter Writer block, which could be a built-in block such as a Gain block, a Model block, a masked subsystem block, or a User-Defined Functions block such as an S-Function block

• The block whose parameter is indirectly written through a workspace variable

It is recommended to use the Parameter Writer block inside a conditionally executed subsystem to improve the simulation performance. For more information about using conditionally executed subsystems, see Conditionally Executed Subsystems and Models.

To write to a base or model workspace variable, a variable created in Simulink.data.Dictionary, mask parameter, or Model block instance parameter with a Parameter Writer block, the variables and the parameters must be used by a parameter owner block or C MEX S-function with run-time tunable parameters.

When a Parameter Writer block writes values with data type other than double (the default data type) to a mask parameter, you must initialize the mask parameter with a value of the same data type as the value written by the Parameter Writer block. To initialize the mask parameter, double-click the block to open the mask dialog box, specify the data type and value of the mask parameter. Alternatively, to initialize mask parameter programmatically, use MaskValues parameter with set_param function. For more information, see Control Masks Programmatically.

In this example shown, a Parameter Writer block writes a value with data type single to a Gain block parameter inside a masked subsystem. The mask parameter is initialized to 1 with data type single.

When a Parameter Writer block writes to an instance parameter with storage class set to Model default, the code generator uses the default configuration for Model parameter arguments when generating code for the parameter. See Specify Instance-Specific Parameter Values for Reusable Referenced Model (Simulink Coder).

Note

When you create a library block with a Parameter Writer block, you must also include the corresponding parameter owner block in the library block. In addition to custom library blocks created using the workflow mentioned in Create Custom Library, Simulink^® treats model components created using Subsystem Reference block as a one-block library.

Identify Parameter Owner Blocks

You can determine whether a block is a supported parameter owner block by the value of the IsParamOwnerBlock block parameter. Use the get_param function with the block name or handle, blk, and the IsParamOwnerBlock block parameter.

get_param(blk,'IsParamOwnerBlock')

The function returns 'on' if the block is a supported parameter owner block and 'off' otherwise.

A Parameter Writer block and the parameter owner block of the value that the block writes constitute a set of related blocks. You can select a Parameter Writer block to highlight the related parameter owner block or vice versa. When a related block is highlighted, blocks in the current model that contain the related block are also highlighted. For example, an Initialize Function block is highlighted when it contains a Parameter Writer block that is related to the selected block. The blocks that are highlighted in the model canvas are also highlighted in the miniature map.

To show a related block in an open diagram or new tab, pause on the ellipsis that appears after selection. Then, select the Related Blocks button from the action bar. Window focus goes to the open diagram or new tab that shows the related block.

Examples

Use Parameter Writer Block to Change Parameter of Block Inside Referenced Model

Use a Parameter Writer block inside an Initialize Function block to change the Gain parameter of a Gain block in a referenced model.The Gain parameter is configured to change at every instance of the model.

• Open Live Script

Common Uses of Parameter Writer Block

Use the Parameter Writer block to change block parameter and variable values.

• Open Live Script

Use Parameter Writer Block to Schedule PID Controller Gain

Use Parameter Writer blocks to schedule PID controller gain coefficients for a nonlinear system.

• Open Live Script

Limitations

A Parameter Writer block cannot be placed in a Simulink function.

Ports

Input

In — Parameter value

scalar | vector

Parameter value written by the block.

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

Parameters

Validate parameter — Option to validate parameter during normal mode simulation

on (default) | off

Since R2023a

Locally enable parameter validation for this block.

When parameter validation is disabled for a Paramer Writer block, normal mode simulation of the block is faster.

Tips

To globally enable or disable parameter validation for Parameter Writer blocks, use the Parameter Writer block validation configuration parameter.

Dependencies

To disable parameter validation for this block, the block must not directly or indirectly change the value of a Model block instance parameter. For example, the block must not change the value of variable or mask parameter that specifies the value of a Model block instance parameter.

Programmatic Use

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

Parameter:	IsParameterValidationOn
Values:	'on' (default) | 'off'

Example: set_param(gcb,'IsParameterValidationOn','off')

Destination — Option to write to variables and parameters

Block parameter (default) | Model workspace variable | Base workspace variable

Since R2024a

Write to block parameters, model workspace variables, base workspace variables, or variables you create in Simulink.data.Dictionary. Select one of these options:

• Block parameter — Write to block parameters.

• Model workspace variable — Write to variables in the model workspace.

• Base workspace variable — Write to variables in the base workspace or variables you create in Simulink.data.Dictionary.

Note

• The Destination parameter replaces the Access model workspace parameter parameter.

• You can switch the active variant during simulation or execution of the generated code by using the Parameter Writer block placed inside a conditionally executed subsystem or in an Initialize Function block, a Reinitialize Function block, a Reset Function block. Set the Destination parameter based on the location of your variant control variable and select the Validate parameter. For more information see Variant Subsystem.

Programmatic Use

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

Parameter:	Destination
Values:	'Block parameter' (default) | 'Model workspace variable' | 'Base workspace variable'

Example: set_param(gcb, Destination="Block parameter")

Workspace variable name — Name of the workspace variable

no default

Specify the name of the workspace variable whose value this block writes.

Note

The Workspace variable name parameter replaces the existing Model workspace parameter name parameter. (since R2023b)

Dependencies

To enable this parameter, select the Model workspace variable or Base workspace variable from the Destination parameter options.

Programmatic Use

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

Parameter:	WorkspaceVariableName
Values:	'' (default) | character vector | string scalar

Example: set_param(gcb,'WorkspaceVariableName','var')

Parameter owner block — Block path of parameter owner block and name of block parameter

no default

Specify the block path of the parameter owner block and the name of the parameter whose value this block writes.

The Parameter Owner Selector Tree provides the writable parameters in a hierarchical tree list. Expand the nodes on the path to the parameter owner block. Then, select the parameter under the parameter owner block.

Tips

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

Dependencies

To enable this parameter, select the Block parameter option from the Destination parameter list.

Programmatic Use

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

First, specify the block path of a parameter owner block using the ParameterOwnerBlock parameter.

Parameter:	ParameterOwnerBlock
Values:	'' (default) | character vector | string scalar
Data Types:	char | string

Example: set_param(gcb,'ParameterOwnerBlock','mymodel/Gain1')

Then, specify the programmatic name of a block parameter of the parameter owner block using the ParameterName parameter.

Parameter:	ParameterName
Values:	'' (default) | character vector | string scalar

Example: set_param(gcb,'ParameterName','Gain')

Block Characteristics

Data Types	Boolean | bus | double | enumerated | fixed point | integer | single
Direct Feedthrough	no
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™.

Version History

R2024a: Write to base workspace variable and variables in data dictionary

You can now use this block to write to base workspace variables and variables you create in a data dictionary in addition to model workspace variables and block parameters. Use the Destination parameter to specify whether you want to write to a variable or a block parameter. Before R2024a, you could use this block to write to model workspace variables or block parameters only.

R2023b: Write to invisible masked subsystem parameters

A Parameter Writer block can write to a masked subsystem parameter that is enabled regardless of whether the mask dialog box displays the parameter.

R2023a: Disable parameter validation during normal mode simulation

Optionally, disable parameter validation that occurs during normal mode simulation for Parameter Writer blocks. When parameter validation is disabled for a Parameter Writer block, normal mode simulation of the block is faster.

To locally enable or disable parameter validation for a Parameter Writer block, use the Validate parameter block parameter.

To globally enable or disable parameter validation for Parameter Writer blocks, use the Parameter Writer block validation configuration parameter.