Enabled Delay
Delay input signal by fixed or variable sample periods when external enable signal is true
Since R2024b
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
u — Data input signal
scalar | vector
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
d — Delay length
scalar
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 — External enable signal
scalar
Enable signal that enables or disables execution of the block. To create this port, select the Show enable port parameter.
Data Types: Boolean
External reset — External reset signal
scalar
External signal that resets execution of the block to the initial condition. To create this port, select the External reset parameter.
Data Types: Boolean
x0 — Initial condition
scalar | vector
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
Port_1 — Output signal
scalar | vector
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
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
Delay length — Delay length
Dialog
(default) | Input port
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 thed
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' |
Initial condition — Initial condition
Dialog
(default) | Input port
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 thex0
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' |
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)' |
Use circular buffer for state — Circular buffer for storing state
off
(default) | on
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' |
Prevent direct feedthrough — Prevent direct feedthrough
off
(default) | on
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' |
Remove delay length check in generated code — Remove delay length out-of-range check
off
(default) | on
Select to remove code that checks for out-of-range delay length.
Check Box | Result | When 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' |
Diagnostic for delay length — Diagnostic checks for delay length
None
(default) | Warning
| Error
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' |
Show enable port — Create enable port
on
(default) | off
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' |
External reset — External state reset
None
(default) | Rising
| Falling
| Either
| Level
| Level hold
Specify the trigger event to use to reset the states to the initial conditions.
Reset Mode | Behavior |
---|---|
None | No reset |
Rising | Reset on a rising edge |
Falling | Reset on a falling edge |
Either | Reset on either a rising or falling edge |
Level | Reset in either of these cases:
|
Level hold | Reset 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' |
Sample time (-1 for inherited) — Discrete interval between sample time hits
-1
(default) | scalar
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
State name — Unique name for block state
''
(default) | alphanumeric string
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:
'' |
State name must resolve to Simulink signal object — Option to require that state names resolve to signal object
off
(default) | on
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™.
HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.
HDL Coder™ provides configuration options that affect HDL implementation and synthesized logic.
Block Parameter Setting | Description |
---|---|
Set External reset to
Level . | Generates a reset port in the HDL code. |
Select Show enable port. | Generates an enable port in the HDL code. |
For Initial condition, set Source to
Dialog and enter the value. | Specifies an initial condition for the block. |
Set Input processing to Columns as channels
(frame based) or Elements as channels (sample
based) . | Expects vector input data, where each element of the vector represents a sample in time. |
If you use a State Control block with the Delay block inside a subsystem in your Simulink model, use these additional settings.
Block Parameter Setting | Description |
---|---|
Set External reset to Level
hold for Synchronous mode and
Level for Classic mode of
the State Control block. | Generates a reset port in the HDL code. |
Set Delay length to zero for a Delay block with an external enable port. | Treated as a wire in only Synchronous mode of the
State Control block. |
Set Delay length to zero for a Delay block with an external reset port. | Treated as a wire in Synchronous and
Classic modes of the State Control
block. |
For more information about the State Control block, see State Control.
This block has one default HDL architecture.
AllowDelayDistribution | Allow delay to be distributed or absorbed during the distributed
pipelining and delay absorption optimizations. The default is
|
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
|
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
|
ResetType | Suppress reset logic generation. The default is |
UseRAM | Map delays to RAM instead of registers. The default is |
You can generate HDL code for the Delay block that has Delay Length set through the
Input port
. Input delay length can be integer types or floating-point types.The code generation supports positive integer values at the 'd' port of the delay block. The delay length set through the input port must be between
0
andUpper limit
, specified in the Block Parameters dialog box.For negative delay length values, HDL Coder translates these negative delay length to
0
.Similarly, if you specify delay length greater than the upper limit, HDL Coder translates the delay length to the
Upper limit
value.Upper limit range is defined by the range of the delay length input data type. For example, if you specify delay length input data type as
uint8
, then the upper limit must not exceed255
.You can use enable and reset ports for the variable integer Delay block.
This block supports code generation for complex signals.
For Initial condition, Source set to
Input port
is not supported for HDL code generation.HDL code generation supports only the Boolean data type at the Reset and Enable ports.
HDL Block Property UseRAM for RAM mapping is not supported for Delay block that has Delay Length set through the
Input port
.The Delay block that has Delay Length set through the
Input port
does not support bus and matrix data input for HDL code generation.
Version History
Introduced in R2024b
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