Compare Capabilities of Composite Interfaces

Step 2 of 2 in Composite Interface Guidelines

Before you implement a piece of your system using a specific type of composite interface, consider whether the type satisfies your requirements for composite interface elements, modeling, and code generation.

To identify which composite interfaces to consider based on high-level guidelines and ideal use cases, see Explore Composite Interfaces.

Composite Interface Elements

Requirement Virtual Buses Nonvirtual Buses Arrays of Buses Arrays

Requirement	Virtual Buses	Nonvirtual Buses	Arrays of Buses	Arrays
Hierarchical elements	Supported Elements of virtual buses can have hierarchy.	Supported Elements of nonvirtual buses can have hierarchy.	Supported While an array of buses is flat, the nested buses can have hierarchy.	Not supported While you can concatenate signals in stages to create an array, the result is flat, as if you used a single block to concatenate the signals.
Elements with different sample times	Supported Elements of virtual buses can have different sample times. For faster model compilation, use the same sample time for each element of a virtual bus. To change the sample time of an input element, use a Rate Transition block.	Not supported All elements of a nonvirtual bus must use the same sample time. Use a Rate Transition block to change the sample time of signals in a bus. For more information, see Modify Sample Times for Nonvirtual Buses.	Not supported All elements of an array of buses must use the same sample time.	Not supported All elements of an array must use the same sample time.
Elements with different data types	Supported Elements of virtual buses can have different data types.	Supported Elements of nonvirtual buses can have different data types.	Supported Top-level elements of arrays of buses must specify the same `Simulink.Bus` object data type. Elements of the nested buses can have different data types.	Not supported All elements of an array must have the same data type.
Variable-size signals	Supported Virtual buses can contain variable-size signals as long as they are not used as inputs to or outputs from a referenced model.	Supported Nonvirtual buses can contain variable-size signals. Signal logging is supported for nonvirtual buses with variable-size signals when running a simulation in normal or accelerator mode. (since R2023a)	Supported Arrays of buses can contain variable-size signals only for simulations in normal mode. Signal logging is supported for arrays of buses with variable-size signals only when running a simulation in normal mode. (since R2023a)	Supported Arrays can contain variable-size signals.
Function-call signals	Supported A virtual bus can contain function-call signals as long as the bus is not defined by a `Simulink.Bus` object.	Not supported Nonvirtual buses do not support function-call signals.	Not supported Arrays of buses do not support function-call signals.	Not supported Arrays do not support function-call signals. To group function-call signals in a virtual vector, see Mux.
Messages	Supported Virtual buses can have message elements as long as they do not also have signal elements.	Not supported Nonvirtual buses cannot contain message elements.	Not supported Arrays of buses cannot contain message elements.	Not supported Arrays cannot contain message elements.
Physical conserving connections	Not supported Simulink^® buses do not support physical conserving connections. To group physical conserving connections, use a Simscape Bus (Simscape) block.	Not supported Simulink buses do not support physical conserving connections.	Not supported Arrays of buses do not support physical conserving connections.	Supported Arrays support physical conserving connections. For more information, see Nonscalar Physical Signal Connections (Simscape).

Hierarchical elements

Supported

Elements of virtual buses can have hierarchy.

Supported

Elements of nonvirtual buses can have hierarchy.

Supported

While an array of buses is flat, the nested buses can have hierarchy.

Not supported

While you can concatenate signals in stages to create an array, the result is flat, as if you used a single block to concatenate the signals.

Elements with different sample times

Supported

Elements of virtual buses can have different sample times.

For faster model compilation, use the same sample time for each element of a virtual bus. To change the sample time of an input element, use a Rate Transition block.

Not supported

All elements of a nonvirtual bus must use the same sample time.

Use a Rate Transition block to change the sample time of signals in a bus. For more information, see Modify Sample Times for Nonvirtual Buses.

Not supported

All elements of an array of buses must use the same sample time.

Not supported

All elements of an array must use the same sample time.

Elements with different data types

Supported

Elements of virtual buses can have different data types.

Supported

Elements of nonvirtual buses can have different data types.

Supported

Top-level elements of arrays of buses must specify the same Simulink.Bus object data type. Elements of the nested buses can have different data types.

Not supported

All elements of an array must have the same data type.

Variable-size signals

Supported

Virtual buses can contain variable-size signals as long as they are not used as inputs to or outputs from a referenced model.

Supported

Nonvirtual buses can contain variable-size signals.

Signal logging is supported for nonvirtual buses with variable-size signals when running a simulation in normal or accelerator mode. (since R2023a)

Supported

Arrays of buses can contain variable-size signals only for simulations in normal mode.

Signal logging is supported for arrays of buses with variable-size signals only when running a simulation in normal mode. (since R2023a)

Supported

Arrays can contain variable-size signals.

Function-call signals

Supported

A virtual bus can contain function-call signals as long as the bus is not defined by a Simulink.Bus object.

Not supported

Nonvirtual buses do not support function-call signals.

Not supported

Arrays of buses do not support function-call signals.

Not supported

Arrays do not support function-call signals.

To group function-call signals in a virtual vector, see Mux.

Messages

Supported

Virtual buses can have message elements as long as they do not also have signal elements.

Not supported

Nonvirtual buses cannot contain message elements.

Not supported

Arrays of buses cannot contain message elements.

Not supported

Arrays cannot contain message elements.

Physical conserving connections

Not supported

Simulink^® buses do not support physical conserving connections.

To group physical conserving connections, use a Simscape Bus (Simscape) block.

Not supported

Simulink buses do not support physical conserving connections.

Not supported

Arrays of buses do not support physical conserving connections.

Supported

Arrays support physical conserving connections. For more information, see Nonscalar Physical Signal Connections (Simscape).

Composite Interface Modeling

Requirement Virtual Buses Nonvirtual Buses Arrays of Buses Arrays

Requirement	Virtual Buses	Nonvirtual Buses	Arrays of Buses	Arrays
Name-based element access	Supported You can access the elements of virtual buses by name.	Supported You can access the elements of nonvirtual buses by name.	Not supported You can access the top-level elements of arrays of buses only by index.	Not supported You can access the elements of an array only by index.
Element access at component input ports	Supported To select elements of a virtual bus at an input port, use In Bus Element blocks.	Supported To select elements of a nonvirtual bus at an input port, use In Bus Element blocks.	Not supported In Bus Element blocks can pass an array of buses through the interface, but they cannot select the index-based elements of arrays of buses.	Not supported In Bus Element blocks can pass an array through the interface, but they cannot select the index-based elements of the array.
Composite interface definition at component input ports	Supported To define an input virtual bus for a model component, specify the virtual bus and its elements with one or more In Bus Element blocks.	Supported To define an input nonvirtual bus for a model component, specify the nonvirtual bus with one or more In Bus Element blocks. For the element that you want to be a nonvirtual bus: Set Data type to a `Simulink.Bus` object. Set Bus virtuality to `nonvirtual`.	Supported To define an input array of buses for a model component, specify the array of buses with an In Bus Element block. For the element that you want to be an array of buses: Set Data type to a `Simulink.Bus` object. Set Bus virtuality to `nonvirtual`. Set Dimensions to an integer greater than 1.	Supported To define an input array for a model component, specify the array with a `Simulink.ValueType` object as the data type of the input.
Composite interface creation at component output ports	Supported To create a virtual bus at an output port, connect the desired elements of the virtual bus to Out Bus Element blocks that correspond to the same output port.	Supported To create a nonvirtual bus at an output port, connect the desired elements of the nonvirtual bus to Out Bus Element blocks that correspond to the same output port. Then, edit the signal attributes of the bus. Set Data type to a `Simulink.Bus` object. Set Bus virtuality to `nonvirtual`.	Not supported Out Bus Element blocks can pass an array of buses through the interface, but they cannot create an array of buses.	Not supported Out Bus Element blocks can pass an array through the interface, but they cannot create an array.
Incremental interface changes using port blocks	Supported You can add, remove, and modify elements of a virtual bus at an interface with or without changing the block diagram by using In Bus Element and Out Bus Element blocks.	Not supported You cannot make incremental interface changes to nonvirtual buses using port blocks. To modify a nonvirtual bus, modify the corresponding `Simulink.Bus` object.	Not supported While you can change the dimensions of an array of buses at an interface by using port blocks, you cannot change the elements at the interface. To modify the elements of an array of buses, modify the corresponding `Simulink.Bus` object or use Selector and Vector Concatenate blocks.	Not supported You cannot make incremental interface changes to arrays using port blocks. To modify an array, use Selector and Vector Concatenate blocks.
Defined interfaces in simulation	Supported To define the properties of a virtual bus, you can use a `Simulink.Bus` object or specify element attributes with In Bus Element and Out Bus Element blocks.	Supported Nonvirtual buses require `Simulink.Bus` objects, which define bus properties.	Supported To define the properties of an array of buses, use a `Simulink.ValueType` object.	Supported To define the properties of an array, use a `Simulink.Signal` or `Simulink.ValueType` object.
Iterative processing of subsystems	Not supported Virtual buses do not support iterative processing of subsystems.	Not supported Nonvirtual buses do not support iterative processing of subsystems. Group nonvirtual buses in arrays of buses to iteratively process them in a subsystem such as a for-each, while-iterator, or for-iterator subsystem.	Supported Arrays of buses let you iterate over a group of nonvirtual buses. Connect the array of buses to a subsystem such as a for-each, while-iterator, or for-iterator subsystem.	Supported Arrays let you iterate over a group of signals. Connect the array to a subsystem such as a for-each, while-iterator, or for-iterator subsystem.

Name-based element access

Supported

You can access the elements of virtual buses by name.

Supported

You can access the elements of nonvirtual buses by name.

Not supported

You can access the top-level elements of arrays of buses only by index.

Not supported

You can access the elements of an array only by index.

Element access at component input ports

Supported

To select elements of a virtual bus at an input port, use In Bus Element blocks.

Supported

To select elements of a nonvirtual bus at an input port, use In Bus Element blocks.

Not supported

In Bus Element blocks can pass an array of buses through the interface, but they cannot select the index-based elements of arrays of buses.

Not supported

In Bus Element blocks can pass an array through the interface, but they cannot select the index-based elements of the array.

Composite interface definition at component input ports

Supported

To define an input virtual bus for a model component, specify the virtual bus and its elements with one or more In Bus Element blocks.

Supported

To define an input nonvirtual bus for a model component, specify the nonvirtual bus with one or more In Bus Element blocks.

For the element that you want to be a nonvirtual bus:

Set Data type to a Simulink.Bus object.
Set Bus virtuality to nonvirtual.

Supported

To define an input array of buses for a model component, specify the array of buses with an In Bus Element block.

For the element that you want to be an array of buses:

Set Data type to a Simulink.Bus object.
Set Bus virtuality to nonvirtual.
Set Dimensions to an integer greater than 1.

Supported

To define an input array for a model component, specify the array with a Simulink.ValueType object as the data type of the input.

Composite interface creation at component output ports

Supported

To create a virtual bus at an output port, connect the desired elements of the virtual bus to Out Bus Element blocks that correspond to the same output port.

Supported

To create a nonvirtual bus at an output port, connect the desired elements of the nonvirtual bus to Out Bus Element blocks that correspond to the same output port. Then, edit the signal attributes of the bus.

Set Data type to a Simulink.Bus object.
Set Bus virtuality to nonvirtual.

Not supported

Out Bus Element blocks can pass an array of buses through the interface, but they cannot create an array of buses.

Not supported

Out Bus Element blocks can pass an array through the interface, but they cannot create an array.

Incremental interface changes using port blocks

Supported

You can add, remove, and modify elements of a virtual bus at an interface with or without changing the block diagram by using In Bus Element and Out Bus Element blocks.

Not supported

You cannot make incremental interface changes to nonvirtual buses using port blocks.

To modify a nonvirtual bus, modify the corresponding Simulink.Bus object.

Not supported

While you can change the dimensions of an array of buses at an interface by using port blocks, you cannot change the elements at the interface.

To modify the elements of an array of buses, modify the corresponding Simulink.Bus object or use Selector and Vector Concatenate blocks.

Not supported

You cannot make incremental interface changes to arrays using port blocks.

To modify an array, use Selector and Vector Concatenate blocks.

Defined interfaces in simulation

Supported

To define the properties of a virtual bus, you can use a Simulink.Bus object or specify element attributes with In Bus Element and Out Bus Element blocks.

Supported

Nonvirtual buses require Simulink.Bus objects, which define bus properties.

Supported

To define the properties of an array of buses, use a Simulink.ValueType object.

Supported

To define the properties of an array, use a Simulink.Signal or Simulink.ValueType object.

Iterative processing of subsystems

Not supported

Virtual buses do not support iterative processing of subsystems.

Not supported

Nonvirtual buses do not support iterative processing of subsystems.

Group nonvirtual buses in arrays of buses to iteratively process them in a subsystem such as a for-each, while-iterator, or for-iterator subsystem.

Supported

Arrays of buses let you iterate over a group of nonvirtual buses. Connect the array of buses to a subsystem such as a for-each, while-iterator, or for-iterator subsystem.

Supported

Arrays let you iterate over a group of signals. Connect the array to a subsystem such as a for-each, while-iterator, or for-iterator subsystem.

Composite Interface Code Generation

Requirement Virtual Buses Nonvirtual Buses Arrays of Buses Arrays

Requirement	Virtual Buses	Nonvirtual Buses	Arrays of Buses	Arrays
Structures in generated code	Not supported Virtual buses do not appear as structures in the generated code. While you can specify a `Simulink.Bus` object data type for a virtual bus, the generated code does not apply the type.	Supported Nonvirtual buses appear as structures in the generated code. The corresponding `Simulink.Bus` objects represent the structure types. For more information, see Organize Data into Structures in Generated Code (Simulink Coder).	Supported Arrays of buses appear as arrays of structures in the generated code. The corresponding `Simulink.Bus` objects represent the structure types.	Not supported Arrays appear as vectors in the generated code. For more information, see Code Generation of Matrices and Arrays (Simulink Coder).
Individual data elements at interface	Supported For a virtual bus, the generated code appears as if the bus did not exist. The code generator is able to fully optimize the signals in a virtual bus. For more information, see Generate Efficient Code for Buses (Simulink Coder).	Not supported A nonvirtual bus is represented as a whole in the generated code. A nonvirtual bus can require data copies.	Not supported An array of buses is represented as a whole in the generated code. An array of buses can require data copies.	Not supported An array is represented as a whole in the generated code. An array can require data copies.

Structures in generated code

Not supported

Virtual buses do not appear as structures in the generated code. While you can specify a Simulink.Bus object data type for a virtual bus, the generated code does not apply the type.

Supported

Nonvirtual buses appear as structures in the generated code. The corresponding Simulink.Bus objects represent the structure types.

For more information, see Organize Data into Structures in Generated Code (Simulink Coder).

Supported

Arrays of buses appear as arrays of structures in the generated code. The corresponding Simulink.Bus objects represent the structure types.

Not supported

Arrays appear as vectors in the generated code.

For more information, see Code Generation of Matrices and Arrays (Simulink Coder).

Individual data elements at interface

Supported

For a virtual bus, the generated code appears as if the bus did not exist. The code generator is able to fully optimize the signals in a virtual bus. For more information, see Generate Efficient Code for Buses (Simulink Coder).

Not supported

A nonvirtual bus is represented as a whole in the generated code. A nonvirtual bus can require data copies.

Not supported

An array of buses is represented as a whole in the generated code. An array of buses can require data copies.

Not supported

An array is represented as a whole in the generated code. An array can require data copies.