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Enabled Delay

Delay input signal by fixed or variable sample periods when external enable signal is true

Since R2024b

  • Enabled Delay block

Libraries:
HDL Coder / Discrete
Simulink / Discrete

Description

The Enabled Delay block outputs a delayed version of the input signal based on the state of the enable signal. At the start of the simulation or upon an enable signal transition to true, the block outputs the initial condition value x0. If the enable signal s true during consecutive time steps, the block continues to output the input signal delayed by specified delay length. If the enable signal is false at the start of the simulation, the block outputs zero. If the enable signal becomes false after begin true, the block maintains the last output value until the enable signal becomes true again. The block supports:

  • Variable delay length

  • State storage

  • Using a circular buffer instead of an array buffer for state storage

  • Resetting the state to the initial condition with an external reset signal

  • Controlling execution of the block at every time step with an external enable signal

Ports

Input

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Input data signal delayed according to parameters settings.

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

Delay length specified as inherited from an input port. Enabled when you select the Delay length: Source parameter as Input port.

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

Enable signal that enables or disables execution of the block. To create this port, select the Show enable port parameter.

Data Types: Boolean

External signal that resets execution of the block to the initial condition. To create this port, select the External reset parameter.

Data Types: Boolean

Initial condition specified as inherited from an input port. Enabled when you select the Initial Condition: Source parameter as Input port.

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

Output

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Output signal that is the input signal delayed by the length of time specified by the parameter Delay length. The initial value of the output signal depends on several conditions. See Delay.

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

Parameters

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To edit block parameters interactively, use the Property Inspector. From the Simulink® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Main

Specify whether to enter the delay length directly on the dialog box (fixed delay) or to inherit the delay from an input port (variable delay).

  • If you set Source to Dialog, enter the delay length in the edit field under Value.

  • If you set Source to Input port, verify that an upstream signal supplies a delay length for the d input port. You can also specify its maximum value by specifying the parameter Upper limit.

Specify the scalar delay length as a real, non-negative integer. An out-of-range or non-integer value in the dialog box (fixed delay) returns an error. An out-of-range value from an input port (variable delay) casts it into the range. A noninteger value from an input port (variable delay) truncates it to the integer.

Programmatic Use

Block Parameter: DelayLengthSource
Type: character vector
Values: 'Dialog' | 'Input port'
Default: 'Dialog'
Block Parameter: DelayLength
Type: character vector
Values: scalar
Default: '2'
Block Parameter: DelayLengthUpperLimit
Type: character vector
Values: scalar
Default: '100'

Specify whether to enter the initial condition directly on the dialog box or to inherit the initial condition from an input port.

  • If you set Source to Dialog, enter the initial condition in the edit field under Value.

  • If you set Source to Input port, verify that an upstream signal supplies an initial condition for the x0 input port.

Simulink converts offline the data type of Initial condition to the data type of the input signal u using a round-to-nearest operation and saturation.

Programmatic Use

Block Parameter: InitialConditionSource
Type: character vector
Values: 'Dialog' | 'Input port'
Default: 'Dialog'
Block Parameter: InitialCondition
Type: character vector
Values: scalar
Default: '0.0'

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. 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)'

Select to use a circular buffer for storing the state in simulation and code generation. Otherwise, an array buffer stores the state.

Using a circular buffer can improve execution speed when the delay length is large. For an array buffer, the number of copy operations increases as the delay length goes up. For a circular buffer, the number of copy operations is constant for increasing delay length.

If one of the following conditions is true, an array buffer always stores the state because a circular buffer does not improve execution speed.

  • For sample-based signals, the delay length is 1.

  • For frame-based signals, the delay length is no larger than the frame size.

Programmatic Use

Block Parameter: UseCircularBuffer
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Select to increase the delay length from zero to the lower limit for the Input processing mode.

  • For sample-based signals, increase the minimum delay length to 1.

  • For frame-based signals, increase the minimum delay length to the frame length.

Selecting this check box prevents direct feedthrough from the input port, u, to the output port. However, this check box cannot prevent direct feedthrough from the initial condition port, x0, to the output port.

Dependency

To enable this parameter, set Delay length: Source to Input port.

Programmatic Use

Block Parameter: PreventDirectFeedthrough
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Select to remove code that checks for out-of-range delay length.

Check BoxResultWhen to Use

Selected

Generated code does not include conditional statements to check for out-of-range delay length.

For code efficiency

Cleared

Generated code includes conditional statements to check for out-of-range delay length.

For safety-critical applications

Dependency

To enable this parameter, set Delay length: Source to Input port.

Programmatic Use

Block Parameter: RemoveDelayLengthCheckInGeneratedCode
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Specify whether to produce a warning or error when the input d is less than the lower limit or greater than the Delay length: Upper limit. The lower limit depends on the setting for Prevent direct feedthrough.

  • If the check box is cleared, the lower limit is zero.

  • If the check box is selected, the lower limit is 1 for sample-based signals and frame length for frame-based signals.

Options for the diagnostic include:

  • None — Simulink software takes no action.

  • Warning — Simulink software displays a warning and continues the simulation.

  • Error — Simulink software terminates the simulation and displays an error.

Dependency

To enable this parameter, set Delay length: Source to Input port.

Programmatic Use

Block Parameter: DiagnosticForDelayLength
Type: character vector
Values: 'None' | 'Warning' | 'Error'
Default: 'None'

Select to control execution of this block with an enable port. The block is considered enabled when the input to this port is nonzero, and is disabled when the input is 0. The value of the input is checked at the same time step as the block execution.

Programmatic Use

Block Parameter: ShowEnablePort
Type: character vector
Values: 'off' | 'on'
Default: 'on'

Specify the trigger event to use to reset the states to the initial conditions.

Reset ModeBehavior
NoneNo reset
RisingReset on a rising edge
FallingReset on a falling edge
EitherReset on either a rising or falling edge
Level

Reset in either of these cases:

  • When the reset signal is nonzero at the current time step

  • When the reset signal value changes from nonzero at the previous time step to zero at the current time step

Level holdReset when the reset signal is nonzero at the current time step

Programmatic Use

Block Parameter: ExternalReset
Type: character vector
Values: 'None' | 'Rising' | 'Falling' | 'Either' | 'Level' | 'Level hold'
Default: 'None'

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. This block supports discrete sample time, but not continuous sample time.

Programmatic Use

Block Parameter: SampleTime
Type: character vector
Value: real scalar
Default: '-1'

State Attributes

Use this parameter to assign a unique name to the block state. The default is ' '. When this field is blank, no name is assigned. When using this parameter, remember these considerations:

  • A valid identifier starts with an alphabetic or underscore character, followed by alphanumeric or underscore characters.

  • The state name applies only to the selected block.

This parameter enables State name must resolve to Simulink signal object when you click Apply.

For more information, see C Data Code Interface Configuration for Model Interface Elements.

Programmatic Use

Block Parameter: StateName
Type: character vector
Values: unique name
Default: ''

Specify whether state names are required to resolve to signal objects. If selected, the software generates an error at run time if you specify a state name that does not match the name of a signal object.

Selecting this parameter disables the Code generation storage class parameter.

Dependencies

Enabled when you specify a value for the State name parameter and set the Signal resolution model configuration parameter to a value other than None.

Programmatic Use

Block Parameter: StateMustResolveToSignalObject
Type: character vector
Values: 'off' | 'on'
Default: 'off'

Extended Capabilities

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

Version History

Introduced in R2024b