Detect Fall Negative

Detect falling edge when signal value decreases to strictly negative value, and its previous value was nonnegative

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  • Library:

  • Simulink / Logic and Bit Operations

  • Detect Fall Negative block

Description

The Detect Fall Negative block determines if the input is less than zero, and its previous value is greater than or equal to zero.

This block supports only discrete sample times.

Ports

For more information, see Data Types Supported by Simulink in the Simulink® documentation.

Input

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Input signal, specified as a scalar, vector, or matrix.

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

Output

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Output signal, true (equal to 1) when the input signal is less than zero, and its previous value was greater than or equal to zero; false (equal to 0) when the input signal is greater than or equal to zero, or if the input signal is negative, its previous value was also negative.

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

Parameters

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Set the initial condition of the Boolean expression U/z < 0.

Programmatic Use

Block Parameter: vinit
Type: character vector
Values: scalar | vector
Default:'0'

Specify whether the block performs sample- or frame-based processing:

  • Columns as channels (frame based) — Treat each column of the input as a separate channel (frame-based processing).

    Note

    Frame-based processing requires a DSP System Toolbox™ license.

    For more information, see Sample- and Frame-Based Concepts (DSP System Toolbox).

  • Elements as channels (sample based) — Treat each element of the input as a separate channel (sample-based processing).

Use Input processing to specify whether the block performs sample- or frame-based processing. The block accepts frame-based signals for the input u. All other input signals must be sample-based.

Input Signal uInput Processing ModeBlock Works?
Sample basedSample basedYes
Frame basedNo, produces an error
Sample basedFrame basedYes
Frame basedYes

For more information about these two processing modes, see Sample- and Frame-Based Concepts (DSP System Toolbox).

Programmatic Use

Block Parameter: InputProcessing
Type: character vector
Values: 'Columns as channels (frame based)' | 'Elements as channels (sample based)'
Default: 'Elements as channels (sample based)'

Set the output data type to boolean or uint8.

Programmatic Use

Block Parameter: OutDataTypeStr
Type: character vector
Values: 'boolean' | 'uint8'
Default: 'boolean'

Model Examples

Detect Fall to Negative Signal Values

Detect Fall to Negative Signal Values

Detect when a signal value decreases to a strictly negative value from a value that was greater than or equal to zero.

Open Model

Block Characteristics

Data Types

Boolean | double | fixed point | integer | single

Direct Feedthrough

yes

Multidimensional Signals

yes

Variable-Size Signals

yes

Zero-Crossing Detection

no

Extended Capabilities

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

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

See Also

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Introduced before R2006a

Simulink Documentation

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