Composite Interfaces

Group signals or messages to reduce model complexity at component interfaces

To reduce model complexity, group individual signals or messages into composite lines using buses.

Virtual buses meet most modeling requirements for composite interfaces and provide the flexibility to combine different types of signals.

For a comparison of modeling techniques, see Composite Interface Guidelines.

Blocks

In Bus Element	Select input from external port
Out Bus Element	Specify output of external port

Bus Assignment	Assign new values to specified bus elements
Bus Creator	Group input signals, buses, or messages into bus
Bus Selector	Select elements from input bus

Demux	Extract and output elements of virtual vector signal
Mux	Combine input signals of same data type and complexity into virtual vector
Selector	Select input elements from vector, matrix, or multidimensional signal
Vector Concatenate	Concatenate input vectors of same data type for iterative processing
Matrix Concatenate	Concatenate input matrices of same data type for iterative processing

Bus to Vector	Convert virtual bus to vector
Signal Conversion	Convert signal to new type without altering signal values

`createBusPort`	Create bus element port from bus block connected to port block (Since R2025a)
`simplifyInterfacesWithBusPorts`	Update model or subsystem file to use bus element ports for buses (Since R2025a)
`Simulink.Bus.addElementToPort`	Add element to input bus element port (Since R2022b)

`getNumLeafBusElements`	Number of leaf elements in `Simulink.Bus` object
`getLeafBusElements`	Leaf elements in `Simulink.Bus` object
`Simulink.Bus`	Specify properties of buses
`Simulink.BusElement`	Specify properties of elements of buses
`Simulink.Bus.cellToObject`	Create `Simulink.Bus` objects from cell array of bus information
`Simulink.Bus.createObject`	Create `Simulink.Bus` objects from blocks or MATLAB structures
`Simulink.Bus.objectToCell`	Create cell array of bus information from `Simulink.Bus` objects
`Simulink.Bus.save`	Save `Simulink.Bus` object definitions in function

Simulink.Bus.createMATLABStruct Create MATLAB structures that use same hierarchy and attributes as buses

Simulink.BlockDiagram.addBusToVector Convert virtual bus signals into vector signals by adding Bus to Vector blocks

Component Interface View	Display component interfaces to trace port connections and author ports
Signal Hierarchy Viewer	View signal hierarchy and trace signal to source or destination
Type Editor	Create, modify, and manage types, such as bus objects

Unspecified bus object at root Outport block	Diagnostic action to take when root Outport block of referenced model does not specify bus object for bus output
Element name mismatch	Diagnostic action to take when bus element name does not match corresponding bus element object name
Bus signal treated as vector	Diagnostic action to take when virtual bus is treated as vector
Non-bus signals treated as bus signals	Diagnostic action to take when nonbus signals are treated as buses
Repair bus selections	Diagnostic action to take when upstream bus hierarchy changes break selections

Composite Interface Guidelines

Combine signals, messages, or connections to simplify model appearance.
- STEP 1: Explore Composite Interfaces
- STEP 2: Compare Capabilities of Composite Interfaces
Bus-Capable Blocks
Identify the blocks that support virtual buses, nonvirtual buses, and arrays of buses.

Group Signals or Messages into Virtual Buses
Create buses to reduce the number of lines in a block diagram.
Simplify Subsystem and Model Interfaces with Bus Element Ports
Group multiple lines into a bus at the input or output of a model component.
Display Bus Information
Display information about buses, such as signal hierarchy and whether the bus is virtual or nonvirtual.
Identify Automatic Bus Conversions
Recognize modeling patterns that cause hidden Bus To Vector and Signal Conversion blocks.
Programmatically Create Bus Element Ports
Add blocks for bus element ports and specify element attributes using MATLAB^® functions.

Modify Bus Hierarchy
Change the order and hierarchy of nested buses and their elements.
Assign Values to Bus Elements
Use a Bus Assignment block to replace signals assigned to bus elements.
Specify Initial Conditions for Bus Elements
Specify bus element values as initial conditions for buses.
Share and Reuse Bus-Routing Blocks
Share blocks that create or interact with buses using subsystem references or custom libraries.

Specify Bus Properties with Bus Objects
Create a reusable bus definition to specify as a data type for a bus.
Programmatically Create Simulink Bus Objects
Use functions to create Simulink.Bus objects from other objects, blocks, or MATLAB data.

Create Nonvirtual Buses
Create buses that appear in generated code and support modeling constructs such as arrays of buses.
Modify Sample Times for Nonvirtual Buses
Make the sample time of signals the same so that you can group them in a nonvirtual bus.
Generate Code for Nonvirtual Buses
Use a structure in code generation to represent a nonvirtual bus. Control data types of initial condition structure fields.
Inspect Generated Code for Nonvirtual Buses
Find nonvirtual buses in generated code for a simple model.

Group Nonvirtual Buses in Arrays of Buses
Streamline a model for iterative processing by combining nonvirtual buses that have the same data type into an array.
Work with Arrays of Buses
Set up your model to use an array of buses to select signals, assign values to a signal, perform iterative processing, log and load signals, and initialize signals.
Iteratively Process Nonvirtual Buses with Arrays of Buses
Update a model to use arrays of buses to apply the same algorithm to multiple nonvirtual buses with the same data type.