Relational Operator

Perform specified relational operation on inputs

• 

Libraries:
Simulink / Commonly Used Blocks
Simulink / Logic and Bit Operations
HDL Coder / Commonly Used Blocks
HDL Coder / HDL Floating Point Operations
HDL Coder / Logic and Bit Operations

Description

The Relational Operator block performs the specified relational operation on the input. The value you choose for the Relational operator parameter determines whether the block accepts one or two input signals.

Two-Input Mode

By default, the Relational Operator block compares two inputs using the Relational operator parameter that you specify. The first input corresponds to the top input port and the second input to the bottom input port. (See Identify Port Location on Rotated or Flipped Block for a description of the port order for various block orientations.)

You can specify one of the following operations in two-input mode:

Operation	Description
==	True if the first input is equal to the second input
~=	True if the first input is not equal to the second input
<	True if the first input is less than the second input
<=	True if the first input is less than or equal to the second input
>=	True if the first input is greater than or equal to the second input
>	True if the first input is greater than the second input

You can specify inputs as scalars, arrays, or a combination of a scalar and an array.

For...	The output is...
Scalar inputs	A scalar
Array inputs	An array of the same dimensions, where each element is the result of an element-by-element comparison of the input arrays
Mixed scalar and array inputs	An array, where each element is the result of a comparison between the scalar and the corresponding array element

If the relational operation can be efficiently and accurately represented on the hardware board, this efficient representation is used. Otherwise, both operands are cast to a common type using overflow saturation and the specified rounding mode.

You can specify the output data type using the Output data type parameter. The output equals 1 for true and 0 for false.

Tip

Select an output data type that represents zero exactly. Data types that satisfy this condition include signed and unsigned integers and any floating-point data type.

One-Input Mode

When you select one of the following operations for Relational operator, the block switches to one-input mode.

Operation	Description
isInf	True if the input is Inf
isNaN	True if the input is NaN
isFinite	True if the input is finite

For an input that is not floating point, the block produces the following output.

Data Type	Operation	Block Output
Fixed point Boolean Built-in integer	isInf	False
	isNaN	False
	isFinite	True

Rules for Data Type Propagation

The following rules apply for data type propagation when your block has one or more input ports with unspecified data types.

When the block is in...	And...	The block uses...
Two-input mode	Both input ports have unspecified data types	double as the default data type for both inputs
	One input port has an unspecified data type	The data type from the specified input port as the default data type of the other port
One-input mode	The input port has an unspecified data type	double as the default data type for the input

Examples

Model Fault-Tolerant Fuel Control System

Combine Stateflow® and Simulink® capabilities to model hybrid systems. This type of modeling is particularly useful for systems that have numerous possible operational modes based on discrete events. Traditional signal flow is handled in Simulink while changes in control configuration are implemented in Stateflow. The model described in this example represents a fuel control system for a gasoline engine. The system is robust in that it detects individual sensor failures, and the control system is dynamically reconfigured for uninterrupted operation.

• Open Model

Ports

Input

Port_1 — First input signal

scalar | vector | matrix

First input signal, specified as a scalar, vector, or matrix.

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated

Port_2 — Second input signal

scalar | vector | matrix

Second input signal, specified as a scalar, vector, or matrix.

Dependencies

To enable this port, set the Relational operator to ==, ~=, <, <=, >=, or >.

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated

Output

Port_1 — Output signal

scalar | vector | matrix

Output signal, consisting of zeros and ones, with the same dimensions as the input. You control the output data type with the Output data type parameter.

Data Types: half | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated

Parameters

Main

Relational operator — Relational operator

<= (default) | ~= | == | < | >= | > | isInf | isNaN | isFinite

Specify the operation for comparing two inputs or determining the signal type of one input.

• == — True if the first input is equal to the second input

• ~= — True if the first input is not equal to the second input

• < — True if the first input is less than the second input

• <= — True if the first input is less than or equal to the second input

• >= — True if the first input is greater than or equal to the second input

• > — True if the first input is greater than the second input

• isInf — True if the input is Inf

• isNaN — True if the input is NaN

• isFinite — True if the input is finite

== and ~= support complex numbers for simulation and code generation.

Programmatic Use

Block Parameter: Operator

Type: character vector

Values: '==' | '~=' | '<' | '<=' | '>=' | '>' | 'isInf' | 'isNaN' | 'isFinite'

Default: '<='

Enable zero-crossing detection — Enable zero-crossing detection

on (default) | off

Select to enable zero-crossing detection. For more information, see Zero-Crossing Detection.

Programmatic Use

Parameter: ZeroCross

Type: character vector, string

Values: 'on' | 'off'

Default: 'on'

Sample time (-1 for inherited) — Interval between samples

-1 (default) | scalar | vector

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. For more information, see Specify Sample Time.

Dependencies

This parameter is visible only if you set it to a value other than -1. To learn more, see Blocks for Which Sample Time Is Not Recommended.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	SampleTime
Values:	"-1" (default) | scalar or vector in quotes

Data Type

Require all inputs to have the same data type — Require all inputs to have same data type

off (default) | on

To require that all block inputs have the same data type, select this check box. When you clear this check box, the inputs can have different data types.

Dependencies

This check box is not available when you set Relational operator to isInf, isNaN, or isFinite because, in those modes, the block only has one input port.

Programmatic Use

Block Parameter: InputSameDT

Type: character vector

Values: 'off' | 'on

Default: 'off'

Output data type — Output data type

boolean (default) | Inherit: Logical (see Configuration Parameters: Optimization) | fixdt(1,16) | <data type expression>

Specify the output data type. When you select:

• boolean — The block output has data type boolean.

• Inherit: Logical (see Configuration Parameters: Optimization) — The block uses the Implement logic signals as Boolean data configuration parameter to specify the output data type (see Implement logic signals as Boolean data (vs. double)).

  Note

  This option supports models created before the boolean option was available. Use one of the other options, preferably boolean, for new models.

• fixdt(1,16) — The block output has the specified fixed-point data type fixdt(1,16).

  Tip

  The Data Type Assistant helps you set data attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant.

• <data type expression> — The block output has the data type you specify as a data type expression, for example, Simulink.NumericType.

  Tip

  To enter a built-in data type (double, single, int8, uint8, int16, uint16, int32, or uint32), enclose the expression in single quotes. For example, enter 'double' instead of double.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'Inherit: Logical (see Configuration Parameters: Optimization)' | 'boolean' | 'fixdt(1,16)' | '<data type expression>'

Default: 'boolean'

Integer rounding mode — Rounding mode for fixed-point operations

Simplest (default) | Convergent | Floor | Nearest | Round | Ceiling | Zero

Specify the rounding mode for fixed-point operations. You can select:

Ceiling

Rounds positive and negative numbers toward positive infinity. Equivalent to the MATLAB^® ceil function.

Convergent

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ convergent function.

Floor

Rounds positive and negative numbers toward negative infinity. Equivalent to the MATLAB floor function.

Nearest

Rounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer nearest function.

Round

Rounds 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 round function.

Simplest

Chooses between rounding toward floor and rounding toward zero to generate rounding code that is as efficient as possible.

Zero

Rounds number toward zero. Equivalent to the MATLAB fix function.

For more information, see Rounding Modes (Fixed-Point Designer).

Programmatic Use

Block Parameter: RndMeth

Type: character vector

Values: 'Ceiling' | 'Convergent' | 'Floor' | 'Nearest' | 'Round' | 'Simplest' | 'Zero'

Default: 'Simplest'

Mode — Category of data to specify

Built in (default) | Inherit | Fixed point | Expression

Select the category of data to specify.

• Built in — Specifies built-in data types. Selecting Built in enables boolean.

• Inherit — Specifies inheritance rules for data types. Selecting Inherit enables Logical (see Configuration Parameters: Optimization).

• Fixed point — Specifies fixed-point data types.

• Expression — Specifies expressions that evaluate to data types.

Dependencies

To enable this parameter, click the Show data type assistant button.

Data type override — Specify data type override mode for this signal

Inherit | Off

Select the data type override mode for this signal.

• When you select Inherit, Simulink inherits the data type override setting from its context, that is, from the block, Simulink.Signal object or Stateflow^® chart in Simulink^® that is using the signal.

• When you select Off, Simulink ignores the data type override setting of its context and uses the fixed-point data type specified for the signal.

For more information, see Specify Data Types Using Data Type Assistant in the Simulink documentation.

Dependencies

To enable this parameter, set Mode to Built in or Fixed point.

Tips

The ability to turn off data type override for an individual data type provides greater control over the data types in your model when you apply data type override. For example, you can use this option to ensure that data types meet the requirements of downstream blocks regardless of the data type override setting.

Signedness — Signedness of fixed-point data

Signed (default) | Unsigned

Specify whether you want the fixed-point data as signed or unsigned. Signed data can represent positive and negative values, but unsigned data represents positive values only. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Mode to Fixed point.

Word length — Bit size of the word that holds the quantized integer

16 (default) | integer from 0 to 32

Specify the bit size of the word that holds the quantized integer. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Mode to Fixed point.

Scaling — Method of scaling

Integer (default)

Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors. Specifying Integer has the same result as specifying a binary point location and setting the fraction length to 0.

Dependencies

To enable this parameter, click the Show data type assistant button and set Mode to Fixed point.

Block Characteristics

Data Types	Boolean | double | enumerated | fixed point | half | integer | single
Direct Feedthrough	yes
Multidimensional Signals	yes
Variable-Size Signals	yes
Zero-Crossing Detection	yes

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has one default HDL architecture.

HDL Block Properties

General
ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see OutputPipeline (HDL Coder).

Native Floating Point
LatencyStrategy	Specify whether to map the blocks in your design to inherit, Max, Min, Zero, or Custom for the floating-point operator. The default is inherit. See also LatencyStrategy (HDL Coder).
NFPCustomLatency	To specify a value, set LatencyStrategy to Custom. HDL Coder adds latency equal to the value that you specify for the NFPCustomLatency setting. See also NFPCustomLatency (HDL Coder).

Complex Data Support

The ~= and == operators are supported for simulation and code generation.

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced before R2006a