Variant Control Modes in Variant Blocks - MATLAB & Simulink (original) (raw)

The components of a Simulink® model that contain variants are activated or deactivated based on the variant choice that you select.

Each variant choice in your model is associated with a variant control. Variant controls determine which variant choice is active. By changing the value of a variant control, you can switch the active variant choice. While each variant choice is associated with a variant control, only one variant control can evaluate totrue. When a variant control evaluates to true, Simulink activates the variant choice that corresponds to that variant control. For a simple example, see Introduction to Variant Controls.

Types of Variant Control Modes in Variant Blocks

These are types of variant control modes in Simulink:

• expression — The software chooses the active variant based on the evaluation of the variant conditions. When a condition expression evaluates totrue, the corresponding variant choice becomes active. When a condition expression evaluates to false, the corresponding variant choice becomes inactive. See Switch Between Choices Using Condition Expressions in Variant Blocks.
• label — The software chooses the active variant based on the name of the variant. The variant control is a string and does not require you to create any variable in any workspaces. See Switch Between Choices Using Labels in Variant Blocks.
• sim codegen switching — Automatically switch between the variants for simulation and code generation workflows without creating any workspace variable. When you simulate a model, the software automatically chooses thesim branch as the active choice. Similarly, when you do a software-in-the-loop (SIL) or processor-In-Loop (PIL) simulation, generate code, or use external mode, the software automatically chooses the codegen branch. See Switch Between Choices for Simulation and Code Generation Workflows Without Using Control Variables in Variant Blocks.

Switch Between Choices Using Condition Expressions in Variant Blocks

In expression mode, Simulink chooses the active variant based on the evaluation of the variant conditions. When a condition expression evaluates to true, the corresponding variant choice becomes active. When a condition expression evaluates to false, the corresponding variant choice becomes inactive.

You can use the expression type of variant controls in variant blocks and in variant parameters.

Note

You can simulate and generate code from the model containing a variant block withVariant control mode set to expression mode. The generated code can contain active and inactive choices that are enclosed in preprocessor conditionals #if and #elif, or regular if conditions.

Use expression Type of Variant Control in Variant Blocks

To specify the variant condition expressions in variant blocks:

• Right-click the badge on the variant block, select , and then specify the variant condition expression in theVariant control expression parameter of the block parameter dialog box.
  Variant control mode: expression
  
• Use this command.
  set_param('Model/Controller/Linear Controller',...
  'VariantControl', 'VSSMODE == 1')
  In this command, Model/Controller/Linear Controller is the full path of the variant choice, and VSSMODE == 1 is the expression associated with the variant choice in the model_Model_.

Types of Variant Controls in expression Mode

The variant controls can be:

• Boolean condition expression for rapid prototyping. For example, A == 1, A ~= B, A && B == 1, and so on.
• A Simulink.VariantExpression object that contains condition expressions for condition reuse. See Simulink.VariantExpression Objects for Variant Condition Reuse of Variant Blocks.
• A default variant control if none of the choices evaluates totrue. You can specify at most one variant choice as the default for the block. During simulation, if none of the variant controls evaluate totrue, Simulink uses the default variant as the active variant choice. To set a variant choice as the default, select the (default) keyword in the Variant control expression column for that choice.

Here, A and B are operands called as_variant control variables_. +,==, and && are operators in the condition expression. The condition expression can contain one or more such variant control variables and operators. For information on supported types and storage location of variant control variables, see Types of Variant Control Variables (Operands) in Variant Blocks and Storage Locations for Variant Control Variables (Operands) in Variant Blocks. For information on operators, see Types of Operators in Variant Blocks for Different Activation Times.

Note

You can comment out the variant controls by placing a % symbol before the control expressions. During simulation, if the corresponding variant choice is active, Simulink ignores the variant choice. However, Simulink continues to execute block callbacks inside the variant choice.

Types of Variant Control Variables (Operands) in Variant Blocks

In expression mode, you can specify the variant control variables as any of these types, from options to use while prototyping to options required for generating code from your model.

For list of all examples, see Use Variant Control Variables in Variant Blocks.

Storage Locations for Variant Control Variables (Operands) in Variant Blocks

You can define the variant control variables in different storage locations based on your requirement. When you define a variable across the base, mask, and model workspaces, the evaluation order begins with the mask workspace, followed by the model workspace, and then the base workspace. This means that the variable's definition in the closest context is prioritized, ensuring that the most relevant value is used for evaluating the variant condition expressions.

Note

• All the variant control variables in a variant block must originate from the same storage location.
• Use Simulink.SimulationInput in the base, mask, and model workspace when the Variant activation time parameter is set to startup. For more information, see Simulink.SimulationInput.
• Define variant control variables for the Initialize Function, Reset Function, Reinitialize Function, and Terminate Function blocks in the following workspaces when the Generate preprocessor conditionals parameter is set to off. However, if the parameter is on, you must define these variables in the base workspace or within a data dictionary, as these are the only allowed storage locations.

For capabilities and advantages of each storage location, see Determine Where to Store Variables and Objects for Simulink Models

Types of Operators in Variant Blocks for Different Activation Times

Variant condition expressions can contain MATLAB® operators, provided the expression evaluates to a Boolean value.

In variant blocks, the operators that you can use to form a variant condition expression depends on the Variant activation time.

When you specify the Variant activation time as:

• update diagram — Any condition expression that evaluates to true or false.
• update diagram analyze all choices orcode compile — The supported operators are:
  • Parentheses for grouping
  • Arithmetic Operators, Relational Operators, Logical Operators, and Bit-Wise Operations, as listed in this table.
    This table lists the MATLAB operators and their representation in the generated code. In these examples, A and B are expressions that evaluate to an integer, and x is a constant integer literal.

    MATLAB Expressions That Support Generation of Preprocessor Conditionals	Equivalent Expression in C Preprocessor Conditional of Generated Code
    Arithmetic
    A + B+A	A + BA
    A - B-A	A - B-A
    A * B	A * B
    idivide(A,B)	A / BIf the value of the second operand (B) is 0, the behavior is undefined.
    rem(A,B)	A % BIf the value of the second operand (B) is 0, the behavior is undefined.
    Relational
    A == B	A == B
    A ~= B	A != B
    A < B	A < B
    A > B	A > B
    A <= B	A <= B
    A >= B	A >= B
    Logical
    ~A	!A, where A is not an integer
    A && B	A && B
    A |	B
    Bitwise (A andB cannot both be constant integer literals)
    bitand(A,B)	A & B
    bitor(A,B)	A | B
    bitxor(A,B)	A ^ B
    bitcmp(A)	~A
    bitshift(A,x)	A << x
    bitshift(A,-x)	A >> x

• startup — The supported operators are:
  • Parentheses for grouping
  • Relational Operators and Logical Operators, as listed in this table.
    This table lists the MATLAB operators and their representation in the generated code. In these examples, A and B are expressions that evaluate to an integer.

    Supported Operators in Variant Condition Expression	Equivalent Expression in Regularif of Generated Code
    Relational
    A == B	A == B
    A ~= B	A != B
    Logical
    ~A	!A, where A is not an integer
    A && B	A && B
    A |	B

Note

In variant blocks with startup activation time:

• For the variant control variables with any activation time, the variant control variables that originate from the mask or the model workspace cannot be used in the MATLAB in-built functions such as idivide,bitand, and so on to form expressions.
• AUTOSAR post-build variants support only == and&& operators. For more information, see Configure Postbuild Variant Conditions for AUTOSAR Software Components (AUTOSAR Blockset).

Evaluate Variant Condition Expressions at Different Variant Activation Times

In expression mode, you can specify if Simulink must evaluate condition expressions during model compile, simulation-loop, code compile, or model start up stage of simulation and code generation workflow using variant activation times. For information on stages of simulation and code generation and supported variant activation times in expression mode, seeActivate Variant During Different Stages of Simulation and Code Generation Workflow.

Automatically Identify Variant Regions Using Variant Condition Propagation

Simulink determines the model components that are active during simulation by the process of variant condition propagation. This process evaluates the variant controls specified on the variant blocks and automatically propagates the variant conditions to the connecting blocks. Variant conditions can propagate through signal lines, buses, and function calls to reach other blocks in the model. The process deactivates the model components associated with the inactive choices and they do not participate in simulation. You can stop condition propagation to define variant regions in the model.

You can limit variant condition propagation in a bounded region using theVariant Start and Variant End blocks. For more information on bounded region, see Variant Start.

You can use the Variant Conditions Legend to visualize the propagated variant conditions that activate each variant choice. Simulink annotates model components if there are variant conditions on them, and the Variant Conditions Legend displays the condition that corresponds to each annotation.

For more information, see Propagate Variant Conditions to Define Variant Regions with Variant Blocks.

Switch Between Choices Using Labels in Variant Blocks

In label mode, Simulink chooses the active variant based on the name of the variant. The variant control is a string and does not require you to create variable in any workspaces.

Use label Mode in Variant Blocks

To specify the labels for choices in variant blocks, right-click the badge on the variant block, select , and then specify the labels in the Variant control label parameter of the block parameter dialog box.

Variant control mode: label

Set Active Choices Using Variant Control Labels

You can follow any of these approaches to set active choices inlabel mode:

• Specify a name for each variant choice in the Variant control label parameter of the variant block dialog box. All the names that you specify are listed in the Label mode active choice drop-down. The label that you select from the list becomes the active choice.
• Right-click the badge on the variant block and select .
• From the mask workspace using the initialization code. Using the mask initialization code, you can specify the active choice from variant block or any subsystem in the hierarchy. The active choice you specify in the mask initialization code overrides the active choice you specify using the Label mode active choice drop-down or the menu item. For more information, see Mask a Variant Subsystem.
• Use this command:
  set_param(blockName,'LabelModeActiveChoice', 'variantChoiceLabel')
  where_blockName_ is the name of the variant block and_variantChoiceLabel_ is the label associated with the variant choice.

Switch Between Choices for Simulation and Code Generation Workflows Without Using Control Variables in Variant Blocks

To automatically switch between the choices for simulation and code generation workflows without creating any workspace variable, use the sim codegen switching variant control mode.

Use sim codegen switching Mode in Variant Blocks

To specify simulation and code generation branches for variant choices, right-click the badge on the variant block, select , and then specify the (sim) and (codegen) keywords in theVariant control switch parameter of the block parameter dialog box.

When you simulate a model in normal, accelerator, or rapid Accelerator mode, 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. The code is generated only for the active choice. Inactive choices are not included in the generated code. In this mode, you can at most have only two choices in the variant block.

Variant control mode: sim codegen switching

Compare Different Types of Variant Control Modes in Variant Blocks

This table explains the capabilities of different variant control modes to help you choose one that caters to your requirement.

Variant Activation Times for Different Variant Control Modes in Variant Blocks

This table explains the variant activation time supported for different variant control modes in variant blocks. For information on variant activation times, see Activate Variant During Different Stages of Simulation and Code Generation Workflow.

See Also

Topics

• Create a Simple Variant Model
• Use Variant Control Variables in Variant Blocks
• Introduction to Variant Controls