Abs

Output absolute value of input

• Library:

• Simulink / Math Operations

  HDL Coder / HDL Floating Point Operations

  HDL Coder / Math Operations

• 

Description

The Abs block outputs the absolute value of the input.

For signed-integer data types, the absolute value of the most negative value is not representable by the data type. In this case, the Saturate on integer overflow check box controls the behavior of the block.

If you...	The block...	And...
Select this check box	Saturates to the most positive value of the integer data type	For 8-bit signed integers, -128 maps to 127. For 16-bit signed integers, -32768 maps to 32767. For 32-bit signed integers, -2147483648 maps to 2147483647.
Do not select this check box	Wraps to the most negative value of the integer data type	For 8-bit signed integers, -128 remains -128. For 16-bit signed integers, -32768 remains -32768. For 32-bit signed integers, -2147483648 remains -2147483648.

The Abs block supports zero-crossing detection. However, when you select Enable zero-crossing detection on the dialog box, the block does not report the simulation minimum or maximum in the Fixed-Point Tool. If you want to use the Fixed-Point Tool to analyze a model, disable zero-crossing detection for all Abs blocks in the model first.

Ports

Input

Port_1 — Input signal

scalar | vector

Input signal to the absolute value block.

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

Output

Port_1 — Absolute value output signal

scalar | vector

Absolute value of the input signal.

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

Parameters

Main

Enable zero-crossing detection — Enable zero-crossing detection

on (default) | Boolean

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

Programmatic Use

Block Parameter: ZeroCross

Type: character vector, string

Values: 'off' | 'on'

Default: 'on'

Sample time — Specify sample time as a value other than -1

-1 (default) | scalar | vector

Specify the sample time as a value other than -1. For more information, see Specify Sample Time.

Dependencies

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

Programmatic Use

Block Parameter: SampleTime

Type: character vector

Values: scalar or vector

Default: '-1'

Signal Attributes

Click the Show data type assistant button to display the Data Type Assistant, which helps you set the data type attributes. For more information, see Specify Data Types Using Data Type Assistant.

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: Same as input (default) | Inherit: Inherit via internal ruleInherit: Inherit via back propagation | | double | single | half | int8 | int32 | uint32 | int64 | uint64 | fixdt(1,16,2^0,0) | <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.

Dependencies

When input is a floating-point data type smaller than single precision, the Inherit: Inherit via internal rule output data type depends on the setting of the Inherit floating-point output type smaller than single precision configuration parameter. Data types are smaller than single precision when the number of bits needed to encode the data type is less than the 32 bits needed to encode the single-precision data type. For example, half and int16 are smaller than single precision.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'Inherit: Same as input' | 'Inherit: Inherit via internal rule'| 'Inherit: Inherit via back propagation' | 'single' | 'half' | 'int8' | 'uint8' | int16 | 'uint16' | 'int32' | 'uint32' | 'int64' | 'uint64' | fixdt(1,16,0) | fixdt(1,16,2^0,0) | fixdt(1,16,2^0,0) | '<data type expression>'

Default: 'Inherit: Same as input'

Lock output data type setting against changes by the fixed-point tools — Prevent fixed-point tools from overriding Output data type

off (default) | on

Select this parameter to prevent the fixed-point tools from overriding the Output data type you specify on the block. 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 — Rounding mode for fixed-point operations

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

Specify the rounding mode for fixed-point operations. For more information, see Rounding (Fixed-Point Designer).

Block parameters always round to the nearest representable value. To control the rounding of a block parameter, enter an expression using a MATLAB^® rounding function into the mask field.

Programmatic Use

Block Parameter: RndMeth

Type: character vector

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

Default: 'Floor'

Saturate on integer overflow — Choose the behavior when integer overflow occurs

off (default) | on

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.

Action	Reason for Taking This Action	What Happens	Example
Select this check box.	Your model has possible overflow and you want explicit saturation protection in the generated code.	Overflows saturate to the maximum value that the data type can represent.	The number 130 does not fit in a signed 8-bit integer and saturates to 127.
Do not select this check box.	You want to optimize efficiency of your generated code.	Overflows wrap to the appropriate value that is representable by the data type.	The number 130 does not fit in a signed 8-bit integer and wraps to -126.

Programmatic Use

Block Parameter: SaturateOnIntegerOverflow

Type: character vector

Value: 'off' | 'on'

Default: 'off'

Model Examples

Friction Model with Hard Stops

Model friction one way in Simulink®. The two integrators in the model calculate the velocity and position of the system, which is then used in the Friction Model to calculate the friction force.

Open Model

Accurate Zero-Crossing Detection

How zero crossings work in Simulink®. In this model, three shifted sine waves are fed into an absolute value block and saturation block. At exactly t = 5, the output of the switch block changes from the absolute value to the saturation block. Zero crossings in Simulink will automatically detect exactly when the switch block changes its output, and the solver will step to the exact time that the event happens. This can be seen by examining the output in the scope.

Open Model

Block Characteristics

Data Types	double | 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 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.

HDL Architecture

This block has a single, 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, or Zero for the floating-point operator. The default is inherit. See also LatencyStrategy (HDL Coder).

Complex Data Support

This block supports code generation for complex signals with floating-point types in Native Floating Point mode.

Code generation for the block with complex signals that use fixed-point types is not supported. To calculate the magnitude of a complex number, use the Complex to Magnitude-Angle HDL Optimized (DSP System Toolbox) block instead.

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

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