Index Vector
Switch output between different inputs based on value of first input
- Library:
Simulink / Signal Routing
HDL Coder / Signal Routing
Description
The Index Vector block is a special configuration of the Multiport Switch block in which you specify one data input and the control
input is zero-based. The block output is the element of the input vector whose index
matches the control input. For example, if the input vector is [18 15 17
10] and the control input is 3, the element that
matches the index of 3 (zero-based) is 10, and that becomes the output value.
To configure a Multiport Switch block to work as an Index
Vector block set Number of data ports to
1 and Data port order to
Zero-based contiguous.
For more information about the Multiport Switch block, see the Multiport Switch block reference page.
Ports
Input
Port_1 — Control signal
scalar
Control signal, specified as a scalar. When the control input is not an integer value, the block truncates the value to an integer by rounding to zero.
For information on control signals of enumerated type, see Guidelines on Setting Parameters for Enumerated Control Port on the Multiport Switch block ref page.
Limitations
If the control signal is numeric, the control signal cannot be complex.
If the control signal is an enumerated signal, the block uses the value of the underlying integer to select a data port.
If the underlying integer does not correspond to a data input, an error occurs.
Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point
0 or 1 — First data input
scalar | vector
First data input, specified as a scalar or vector. The port is labeled
0 when you set Data port
order to Zero-based
contiguous, and labeled 1 when you
set Data port order to One-based
contiguous.
Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | bus | enumerated | string
Output
Port_1 — Selected data input, based on control signal value
scalar
The block outputs the selected value from the input data vector, according to the control signal value. The output is a scalar.
Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus
Parameters
Main
Data port order — Type of ordering for data input ports
Zero-based
contiguous (default) | One-based contiguous | Specify indices
Specify the type of ordering for your data input ports.
Zero-based contiguous— Block uses zero-based indexing for ordering contiguous data ports. This is the default value of the Index Vector block.One-based contiguous— Block uses one-based indexing for ordering contiguous data ports. This is the default value of the Multiport Switch block.Specify indices— Block uses noncontiguous indexing for ordering data ports. This value is supported only for configurations with two or more input data ports.
Tips
When the control port is of enumerated type, select
Specify indices.If you select
Zero-based contiguousorOne-based contiguous, verify that the control port is not of enumerated type. This configuration is deprecated and produces an error. You can run the Upgrade Advisor on your model to replace each Multiport Switch block of this configuration with a block that explicitly specifies data port indices. See Model Upgrades.Avoid situations where the block contains unused data ports for simulation or code generation. When the control port is of fixed-point or built-in data type, verify that all data port indices are representable with that type. Otherwise, the following block behavior occurs:
If the block has unused data ports and data port order is: The block produces: Zero-based contiguousorOne-based contiguousA warning Specify indicesAn error
Dependencies
Selecting Zero-based contiguous or
One-based contiguous enables the
Number of data ports parameter.
Selecting Specify indices enables the
Data port indices parameter.
Programmatic Use
Block Parameter:
DataPortOrder
|
| Type: character vector |
Values:
'Zero-based contiguous' | 'One-based contiguous' |
'Specify indices' |
Default:
'Zero-based contiguous' |
Number of data ports — Number of data input ports
1 (default) | integer between 1 and 65536
Specify the number of data input ports to the block.
Dependencies
To enable this parameter, set Data port order
to Zero-based contiguous or
One-based contiguous.
Programmatic Use
Block Parameter:
Inputs
|
| Type: character vector |
| Values: integer between 1 and 65536 |
Default:
'1' |
Signal Attributes
Require all data port inputs to have the same data type — Require all inputs to have the same data type
off (default) | on
Select this check box to require that all data input ports have the same data type. When you clear this check box, the block allows data port inputs to have different data types.
Programmatic Use
Block Parameter: InputSameDT |
| Type: character vector |
Values: 'off' | 'on' |
Default: 'off' |
Output minimum — Minimum output value for range checking
[] (default) | scalar
Lower value of the output range that Simulink® checks.
Simulink uses the minimum to perform:
Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.
Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).
Automatic scaling of fixed-point data types.
Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).
Note
Output minimum does not saturate or clip the actual output signal. Use the Saturation block instead.
Programmatic Use
Block Parameter:
OutMin |
| Type: character vector |
Values: '[ ]'|
scalar |
Default: '[ ]' |
Output maximum — Maximum output value for range checking
[] (default) | scalar
Upper value of the output range that Simulink checks.
Simulink uses the maximum value to perform:
Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.
Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).
Automatic scaling of fixed-point data types.
Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).
Note
Output maximum does not saturate or clip the actual output signal. Use the Saturation block instead.
Programmatic Use
Block Parameter:
OutMax |
| Type: character vector |
Values: '[ ]'|
scalar |
Default: '[ ]' |
Output data type — Specify the output data type
Inherit: Inherit via internal
rule (default) | Inherit: Inherit via back propagation | double | single | half | int8 | uint8 | int16 | uint16 | int32 | uint32 | int64 | uint64 | fixdt(1,16) | fixdt(1,16,0) | fixdt(1,16,2^0,0) | string | <data type expression>
Choose the data type for the output. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.
When you select an inherited option, the block behaves as follows:
Inherit: Inherit via internal rule—Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware. If you change the embedded target settings, the data type selected by the internal rule might change. It is not always possible for the software to optimize code efficiency and numerical accuracy at the same time. If the internal rule doesn’t meet your specific needs for numerical accuracy or performance, use one of the following options:Specify the output data type explicitly.
Explicitly specify a default data type such as
fixdt(1,32,16)and then use the Fixed-Point Tool to propose data types for your model. For more information, seefxptdlg(Fixed-Point Designer).To specify your own inheritance rule, use
Inherit: Inherit via back propagationand then use a Data Type Propagation block. Examples of how to use this block are available in the Signal Attributes library Data Type Propagation Examples block.
Inherit: Inherit via back propagation— Uses the data type of the driving block.
Programmatic Use
Block Parameter: OutDataTypeStr |
| Type: character vector |
Values: 'Inherit: Inherit via internal
rule | 'Inherit: Inherit via back
propagation' | 'double' |
'single' | 'half' |
'int8' | 'uint8' |
'int16' |
'uint16' |
'int32' |
'uint32' |
'int64'
| 'uint64'
| 'fixdt(1,16)' |
'fixdt(1,16,0)' |
'fixdt(1,16,2^0,0)' | 'string' |
'<data type expression>' |
Default: 'Inherit: Inherit via internal rule' |
Lock output data type setting against changes by the fixed-point tools — Prevent fixed-point tools from overriding data types
off (default) | on
Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor. For more information, see Use Lock Output Data Type Setting (Fixed-Point Designer).
Programmatic Use
Block Parameter:
LockScale |
| Type: character vector |
Values:
'off' |
'on' |
Default:
'off' |
Integer rounding mode — Specify the rounding mode for fixed-point operations
Floor (default) | Ceiling | Convergent | Nearest | Round | Simplest | Zero
Choose one of these rounding modes.
CeilingRounds both positive and negative numbers toward positive infinity. Equivalent to the MATLAB®
ceilfunction.ConvergentRounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™
convergentfunction.FloorRounds both positive and negative numbers toward negative infinity. Equivalent to the MATLAB
floorfunction.NearestRounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer
nearestfunction.RoundRounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer
roundfunction.SimplestAutomatically chooses between round toward floor and round toward zero to generate rounding code that is as efficient as possible.
ZeroRounds number toward zero. Equivalent to the MATLAB
fixfunction.
Programmatic Use
Block Parameter:
RndMeth |
| Type: character vector |
Values:
'Ceiling' |
'Convergent' |
'Floor' |
'Nearest' |
'Round' |
'Simplest' |
'Zero' |
Default:
'Floor' |
See Also
For more information, see Rounding (Fixed-Point Designer).
Saturate on integer overflow — Method of overflow action
off (default) | on
Specify whether overflows saturate or wrap.
off— Overflows wrap to the appropriate value that the data type can represent.For example, the number 130 does not fit in a signed 8-bit integer and wraps to -126.
on— Overflows saturate to either the minimum or maximum value that the data type can represent.For example, an overflow associated with a signed 8-bit integer can saturate to -128 or 127.
Tip
Consider selecting this check box when your model has a possible overflow and you want explicit saturation protection in the generated code.
Consider clearing this check box when you want to optimize efficiency of your generated code.
Clearing this check box also helps you to avoid overspecifying how a block handles out-of-range signals. For more information, see Troubleshoot Signal Range Errors.
When you select this check box, saturation applies to every internal operation on the block, not just the output or result.
In general, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.
Programmatic Use
Block Parameter: SaturateOnIntegerOverflow |
| Type: character vector |
Values: 'off' | 'on' |
Default: 'off' |
Allow different data input sizes (Results in variable-size output signal) — Allow input signals with different sizes
off (default) | on
Select this check box to allow input signals with different sizes.
On— Allows input signals with different sizes, and propagate the input signal size to the output signal. In this mode, the block produces a variable-size output signal.Off— Requires that all nonscalar data input signals be the same size.
Programmatic Use
Parameter: AllowDiffInputSizes |
| Type: character vector |
Value: 'on' | 'off' |
Default: 'off' |
Model Examples
Block Characteristics
Data Types |
|
Direct Feedthrough |
|
Multidimensional Signals |
|
Variable-Size Signals |
|
Zero-Crossing Detection |
|
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.
HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.
The Index Vector block is a Multiport Switch block with Number of data ports set to 1. For HDL code generation information, see Multiport Switch.