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Tip Simulink® provides several techniques for combining signals into a composite signal. For a comparison of techniques, see Techniques for Combining Signals.
An array of buses is an array whose elements are buses. Each element in an array of buses must be nonvirtual and must have the same bus type. Each bus object has the same signal name, hierarchy, and attributes for its bus elements.
An example of using an array of buses is to model a multi-channel communication system. You can model all of the channels using the same bus object, although each of the channels could have a different value.
Using arrays of buses involves:
Using a bus object as a data type (see Specify a Bus Object Data Type)
Specifying dimensions for the bus and bus elements
For an example of a model that uses an array of buses, open the sldemo_bus_arrayssldemo_bus_arrays model. In this example, the nonvirtual bus input signals connect to a Vector Concatenate or Matrix Concatenate block that creates an array of bus signals. When you update the diagram, the model looks like the following figure:
The model uses the array of buses with:
An Assignment block, to assign a bus in the array
A For Each Subsystem block, to perform iterative processing over each bus in the array
A Memory block, to output the array of buses input from the previous time step
Using an array of buses:
Represents structured data compactly
Reduces model complexity
Reduces maintenance by centralizing algorithms used for processing multiple buses
Streamlines iterative processing of multiple buses of the same type, for example, by using a For Each Subsystem with the array of buses
Simplifies changing the number of buses, without your having to restructure the rest of the model or make updates in multiple places in the model
Allows models to use built-in blocks, such as the Assignment or Selector blocks, to manipulate arrays of buses just like arrays of any other type, rather than your creating custom S-functions to manage packing and unpacking structure signals
Supports using the combined bus data across subsystem boundaries, model reference boundaries, and into or out of a MATLAB Function block
Allows you to keep all the logic in the Simulink model, rather than splitting the logic between C code and the Simulink model
Supports integrated consistency and correctness checking, maintaining metadata in the model, and avoids your keeping track of model components in two different environments
Generates code that has an array of C structures, which you can integrate with legacy C code that uses arrays of structures
Simplifies indexing into an array for Simulink computations, using a for loop on indexed structures
The buses combined into an array must all:
Have the same bus type (that is, same name, hierarchies, and attributes for the bus elements)
Have no variable-size signals or frame-based signals
You can use arrays of buses with the following blocks:
Several nonvirtual blocks, such as:
Some signal routing blocks (for example, Data Store Memory, Merge, and Switch)
Rate Transition and Zero-Order Hold blocks
Several additional blocks, such as Assignment, MATLAB Function, and Signal Conversion
For a complete list, see Blocks That Support Arrays of Buses. That section describes requirements for using the supported blocks.
The following limitations apply to using structure parameters with an array of buses.
You can use:
0 as an initial condition for an array of buses
A scalar struct that represents the same hierarchy and names as the array of buses
You cannot use:
An array of structures
A structure parameter for an array of buses that has an element that is an array of buses
For more information, see Specify Initial Conditions for Bus Signals.
Simulink does not log signals inside referenced models in Rapid Accelerator mode.
Stateflow® action language does not support arrays of buses.
For information about the kinds of buses that you can combine into an array of buses, see Bus Limitations.
To define an array of buses, use a Concatenate block. The table describes the array of buses input requirements and output for each of the Vector Concatenate and the Matrix Concatenate versions of the Concatenate block.
|Block||Bus Signal Input Requirement||Output|
Vectors, row vectors, or columns vectors
If any of the inputs are row or column vectors, output is a row or column vector.
Signals of any dimensionality (scalars, vectors, and matrices)
Trailing dimensions are assumed to be 1 for lower dimensionality inputs.
Concatenation is on the dimension that you specify with the Concatenate dimension parameter.
Note: Do not use a Mux block or a Bus Creator block to define an array of buses. Instead, use a Bus Creator block to create scalar bus signals.
Define one bus object to use for all of the buses that you want to combine into an array of buses. For information about defining bus objects, see Create Bus Objects.
The sldemo_bus_arrays_busobject model uses a Vector Concatenate block, because the inputs are scalars.
Set the Number of inputs parameter to be the number of buses that you want to be in the array of buses.
The block icon displays the number of input ports that you specify.
Set the Mode parameter to match the type of the input bus data.
In the sldemo_bus_arrays model, the input bus data is scalar, so the Mode setting is Vector.
If you use a Matrix Concatenation block, set the Concatenate dimension parameter to specify the output dimension along which to concatenate the input arrays. Enter one of the following values:
1 — concatenate input arrays vertically
2 — concatenate input arrays horizontally
A higher dimension than 2 — perform multidimensional concatenation on the inputs
Connect to the Concatenate block all of the buses that you want to be in the array of buses.