Documentation

Detect Fall Nonpositive

Detect falling edge when signal value decreases to nonpositive value, and its previous value was strictly positive

Library

Logic and Bit Operations

Description

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

  • The output is true (equal to 1) when the input signal is less than or equal to zero, and its previous value was greater than zero.

  • The output is false (equal to 0) when the input signal is greater than zero, or if it is nonpositive, its previous value was also nonpositive.

Data Type Support

The Detect Fall Nonpositive block accepts signals of the following data types:

  • Floating point

  • Built-in integer

  • Fixed point

  • Boolean

For more information, seeData Types Supported by Simulinkin the Simulink®documentation.

Parameters

Initial condition

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

Input processing

Specify whether the block performs sample- or frame-based processing. You can select one of the following options:

  • Elements as channels (sample based)— Treat each element of the input as a separate channel (sample-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, seeSample- and Frame-Based Concepts(DSP System Toolbox) in the DSP System Toolbox documentation.

  • Inherited— Inherit the processing mode from the input signal and delay the input accordingly. You can identify whether the input signal is sample or frame based by looking at the signal line. Simulink represents sample-based signals with a single line and frame-based signals with a double line.

    Note

    When you choose theInheritedoption for theInput processingparameter, and the input signal is frame-based, Simulink will generate a warning or error in future releases.

UseInput processingto specify whether the block performs sample- or frame-based processing. The block accepts frame-based signals for the inputu. All other input signals must be sample based.

Input Signal u Input Processing Mode Block Works?
Sample based Sample based Yes
Frame based No, produces an error
Sample based Frame based Yes
Frame based Yes
Sample based Inherited Yes
Frame based Yes

For more information about these two processing modes, seeSample- and Frame-Based Concepts(DSP System Toolbox) in the DSP System Toolbox documentation.

Output data type

Set the output data type tobooleanoruint8.

Characteristics

Data Types

Double | Single | Boolean | Base Integer | Fixed-Point

Direct Feedthrough

Yes

Multidimensional Signals

No

Variable-Size Signals

Yes

Code Generation

Yes

Introduced before R2006a

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