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Variant Source

Route among multiple inputs using Variants

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  • Library:

  • Simulink / Signal Routing

  • Variant Source block

Description

The Variant Source block has one or more input ports and one output port. You can define Variant choices as blocks that are connected to the input port so that, at most, one choice is active.

Each input port is associated with a Variant control. The Variant control that evaluates to true, determines which input port is active.

When the Variant activation time option in the block dialog box is set to update diagram, then during simulation Simulink® connects the active choice directly to the output port of the Variant Source block and ignores the inactive choices.

Note

Sample time for single input Variant Source blocks can differ with multiple input Variant Source blocks. For more information on sample time, see What Is Sample Time?

Ports

Input

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Input port associated with the first Variant control. The Variant control that evaluates to true, determines which input port is active.

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

Input port associated with the Nth Variant control. The Variant control that evaluates to true, determines which input port is active.

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

Output

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Output signal from the active Variant.

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

Parameters

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  • expression— To choose the active Variant based on the evaluation of the Variant conditions, use expression mode. The Variant control variables used in the Variant condition must be created in a global workspace or in a data dictionary.

  • Label— To choose the active Variant based on the name of the Variant you specify in the Label mode active choice parameter, use label mode. In label mode, the Variant control is a string and does not need to be created in any workspaces.

    When you select label mode, the Variant badge indicates the change.

    Note

    When you promote the Label mode active choice parameter to a mask, Variant control mode is disabled.

    • If the block is in expression mode while promoting the Label mode active choice parameter to a mask, you can change the Variant control mode to label by changing the promoted Label mode active choice parameter from the Mask dialog box.

    • If the block is in label mode while promoting the Label mode active choice parameter to a mask, you cannot change the Variant control mode to expression mode.

    For information about promoting parameters to masks, see Promote Parameter to Mask.

  • sim codegen switching— To automatically switch between the Variants for simulation and code generation workflows, use sim codegen switching mode. When you simulate (Normal , Accelerator, Rapid Accelerator) a model, then Simulink automatically chooses the sim branch as the active choice. Similarly, when you do a Software-in-the-loop (SIL), Processor-In-Loop (PIL) simulation or generate code or use external mode, Simulink automatically chooses the codegen branch.

When you set this parameter to different values, the Variant badge changes as shown in Variant Badges.

Dependencies

The Variant activation time parameter is available only when you set the Variant control mode parameter to expression or sim codegen switching.

This parameter determines if Simulink sets the active choice of a Variant Source block during update diagram or code compile. This parameter also determines which variability to include in the generated code for ERT targets. If you choose to include all the Variant choices, the choices are enclosed within C preprocessor conditional statements (#if and #endif) in the generated code.

When you set this parameter to different values, the variant badge changes as shown in Variant Badges.

You can set the Variant activation time parameter as:

  • update diagram— Simulink sets the active choice during update diagram before the propagation of signal attributes. Inactive choices are removed prior to propagation of signal attributes, so the generated code contains only active choice.

  • update diagram analyze all choices— Simulink sets the active choice during update diagram after the propagation of signal attributes. Signal attributes are propagated to both active and inactive choices. All choices are analyzed to ensure consistency of all variant branches between the results of simulation and code generation. Inactive choices are removed at the end of update diagram before model start occurs. The generated code contains only active choices. This workflow remains the same for simulation and code generation.

  • code compile— For simulation, the workflow is same as the update diagram analyze all choices. However, the inactive choices are not removed during code generation. The generated code contains active and inactive choices, and the choices are enclosed in C preprocessor conditional statements, #if and #endif.

  • startup— When you execute the model, both active and inactive choices are analyzed for consistency across the model and the choices participate in the simulation and the code generation workflow. With this option, you can improve the speed of iterative simulations using fast restart. For more information, see How Fast Restart Improves Iterative Simulations. The code that you generate from the model contains both active and inactive choices that are enclosed in regular if conditions. The executable that you build from the generated code also contains both active and inactive choices.

This figure shows the Variant activation time for the different values you specify in this parameter.

For more information, see Represent Variant Source and Sink Blocks in Generated Code (Embedded Coder).

Dependencies

The availability of different variant activation times depends on the type of the variant control mode that you specify. The Variant activation time parameter determines the time frame when Simulink sets the active choice. The parameter also determines which variability to include in the generated code. This table explains the variant activation time supported by each variant control mode.

Variant activation time
Variant control mode update diagramupdate diagram analyze all choicescode compilestartup
expression✓✓✓✓
label✓xxx
sim codegen switching✓✓xx

Programmatic Use

Block Parameter: VariantActivationTime
Type: character vector
Values: update diagram | update diagram analyze all choices |code compile
Default: update diagram

Number of the input port that is connected to one Variant choice upstream of the Variant Source block. This value is read-only.

Click to add a port or to delete an existing one.

Displays the Variant controls available in the global workspace. The Variant control can be a Boolean condition expression or a Simulink.Variant object representing a Boolean condition expression. If you want to generate code for your model, you must define the control variables as Simulink.Parameter objects.

To enter non-numeric Variant control values, use enumerated data. For information about using enumerated data, see Use Enumerated Data in Simulink Models

To edit a Variant name, double-click a Variant control expression cell and type in the Variant control expression. Click Apply after you edit a Variant control name. If you add or delete a Variant control without applying the changes, the previous edits on the Variant control name are lost.

The Variant control that evaluates to true determines which input port must be active.

Programmatic Use

Block Parameter: VariantControls
Type: cell array of character vectors
Value: Variant control that is associated with the Variant choice
Default: 'Variant'

Displays the Condition for the Variant controls that are Simulink.Variant objects. Create or change a Variant condition in the Simulink.Variant parameter dialog box or in the global workspace.

For more information, see Create Variant Controls Programmatically and Simulink.Variant.

When you select the Variant control mode as Label, the Label mode active choice option is available. You can select an active Variant choice from Label mode active choice options. You can also right-click the badge on the Variant Source block and select Label Mode Active Choice.

The Label mode active choice drop-down list displays all Variant controls that are currently defined in the global workspace or a data dictionary. Use valid MATLAB® identifiers to specify Variant controls. For more information, see Simulink.Variant.

Note

Label mode active choice option is not available in Expression mode.

Dependencies

To enable this parameter, select Label mode.

Programmatic Use

Block Parameter: LabelModeActivechoice
Type: character vector
Value: Specified by the Variant control expression.
Default: Choice_1

To simulate a model (containing a Variant block) without an active Variant choice, select the Allow zero active variant controls option. When this option is selected and there is no active Variant choice, Simulink disables all the blocks connected to the input and output stream of Variant Source block. The removed blocks are ignored from update diagram or simulation.

If you do not select this option, Simulink generates an error when there is no active Variant choice.

When you select this option, the Variant badge indicates the change.

Dependencies

Expression option from Variant control mode is selected.

Programmatic Use

Block Parameter: AllowZeroVariantControls
Type: character vector
Values: 'off' | 'on'
Default: 'off'

When you select this option, Simulink annotates each Variant control (condition expression) on the Variant Source block ports.

Programmatic Use

Block Parameter: ShowConditionOnBlock
Type: character vector
Value: 'off' | 'on'
Default: 'off'

Model Examples

Variant Source and Variant Sink Blocks

Variant Source and Variant Sink Blocks

Define variant choice in Variant Source and Sink blocks.

Control Variant Condition Propagation

Control Variant Condition Propagation

Control propagation of variant conditions upstream and downstream.

Block Characteristics

Data Types

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

Direct Feedthrough

no

Multidimensional Signals

no

Variable-Size Signals

no

Zero-Crossing Detection

no

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™.

See Also

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Topics

Introduced in R2016a

Simulink Documentation

Support

Model-Based Design for Embedded Control Systems

Model-Based Design for Embedded Control Systems

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