Detect Fall Nonpositive

R2026b

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

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Detect Fall Nonpositive block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Simulink / Logic and Bit Operations
HDL Coder / 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.

This block supports only discrete sample times.

Examples

Detect Falling Edge Using the Detect Fall Nonpositive Block

This example shows how to use the Detect Fall Nonpositive block to detect a falling edge in the input signal. The block detects a falling edge when the signal value decreases from a strictly positive value to a nonpositive value. In this example, the Initial condition of the Detect Fall Nonpositive block is set to 1. This means that the Boolean expression U/z <= 0 evaluates to true and the block assumes the initial value of the input signal is nonpositive.

Ports

Input

Port_1 — Input signal

scalar | vector | matrix

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

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

Output

Port_1 — Output signal

scalar | vector | matrix

Output signal that detects a falling edge, specified as a scalar, vector, or matrix.

• 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 Types: uint8 | Boolean

Parameters

Initial condition — Initial condition of Boolean expression U/z <= 0

0 (default) | scalar | vector | matrix

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

Programmatic Use

Block Parameter: vinit

Type: character vector

Values: scalar | vector | matrix

Default: '0'

Input processing — Specify sample- or frame-based processing

Elements as channels (sample based) (default) | Columns as channels (frame based)

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. 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)'

Output data type — Output data type

boolean (default) | uint8

Specify the output data type as boolean or uint8.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'boolean' | 'uint8'

Default: 'boolean'

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Direct Feedthrough	yes
Multidimensional Signals	yes
Variable-Size Signals	yes
Zero-Crossing Detection	no

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"simulink/Logic and Bit Operations/Detect Fall Nonpositive"

"hdlsllib/Logic and Bit Operations/Detect Fall Nonpositive"

Example: add_block("simulink/Logic and Bit Operations/Detect Fall Nonpositive","myModel/myBlock",MakeNameUnique="on")

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Generated code relies on memcpy or memset functions (string.h) under certain conditions.

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

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays in the design. Distributed pipelining does not redistribute these registers. The default value 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 value 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 value is 0. For more details, see OutputPipeline (HDL Coder).
SynthesisAttributes	Specifies the synthesis attributes for the blocks and block output signals in the model. The generated HDL code contains these attributes. For more information, see SynthesisAttributes (HDL Coder).

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

R2026a: Specify synthesis attributes for blocks and block output signals

Use the SynthesisAttributes HDL block property to specify the synthesis attributes for the block and its output signals. HDL Coder includes these attributes in the generated HDL code.