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Trigger

Add trigger or function port to subsystem or model

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  • Trigger block

Libraries:
Simulink / Ports & Subsystems
HDL Coder / Ports & Subsystems

Description

The Trigger block adds an external signal or message port to control the execution of a subsystem or a model. To enable this functionality, add this block to a Subsystem block or at the root level of a model that is referenced in a Model block.

Then, configure the Trigger block to execute a subsystem or model:

  • Once at each time step, when the value of the control signal changes in a way that you specify.

  • Multiple times during a time step, when the control signal is a function-call event from a Stateflow® chart, Function-Call Generator block, or S-Function block.

  • Based on messages received at the control port.

Examples

Triggered Subsystems

Triggered Subsystems

Model showing triggered subsystems and different types of triggers.

Open Model
Using Message Polling and Message Triggered Subsystems

Using Message Polling and Message Triggered Subsystems

Demonstrate and compare Message Triggered Subsystems and Message Polling Subsystems.

Open Model
Model Reference Function-Call

Model Reference Function-Call

Use a Model block that is explicitly triggered by means of its function-call trigger port.

Open Model
Block Priority

Block Priority

What happens when blocks are assigned different priorities. The block priority affects the order in which the blocks are executed. You can set the block priority through the Block Properties dialog. A smaller number indicates a higher priority.

Open Model
Bang-Bang Control Using Temporal Logic

Bang-Bang Control Using Temporal Logic

Use Stateflow® to model a bang-bang temperature control system for a boiler. The boiler dynamics are modeled in Simulink®.

Open Script
Modeling Engine Timing Using Triggered Subsystems

Modeling Engine Timing Using Triggered Subsystems

Model a four-cylinder spark ignition internal combustion engine from the throttle to the crankshaft output. We used well-defined physical principles supplemented, where appropriate, with empirical relationships that describe the system's dynamic behavior without introducing unnecessary complexity.

Open Model
Engine Timing Model with Closed Loop Control

Engine Timing Model with Closed Loop Control

Enhance a version of the open-loop engine model described in Modeling Engine Timing Using Triggered Subsystems. This model, sldemo_enginewc, contains a closed-loop and shows the flexibility and extensibility of Simulink® models. In this enhanced model, the objective of the controller is to regulate engine speed with a fast throttle actuator, such that changes in load torque have minimal effect. This is easily accomplished in Simulink by adding a discrete-time PI controller to the engine model.

Open Model

Ports

Output

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If the Trigger type is rising, falling, either, or function-call, the port outputs a value that identifies a control signal, returned as a scalar or vector. For each element of the input signal, the value at a given time step is:

  • 1 for a signal that causes a rising trigger

  • -1 for a signal that causes a falling trigger

  • 2 for a function-call event

  • 0 in all other cases

If the Trigger type is message, the port outputs data extracted from message received at the control port.

Dependencies

To enable this port, select Show output port or select message from the Trigger type list.

Data Types: double | int8

Parameters

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Main

Select the type of control signal that executes a subsystem or model.

rising

Trigger execution of subsystem or model when the control signal rises from a negative or zero value to a positive value. If the initial value is negative, a rising signal to zero triggers execution.

falling

Trigger execution of subsystem or model when the control signal falls from a positive or a zero value to a negative value. If the initial value is positive, a falling signal to zero triggers execution.

either

Trigger execution of subsystem or model when the control signal is either rising or falling.

function-call

Execute subsystem or model when the control port receives a function-call event from a Stateflow chart, Function-Call Generator block, S-Function block, or Hit Crossing block.

message

Trigger execution of subsystem when a message is available at the control port.

Note

If Trigger type is set to message, the block must be placed inside a subsystem.

Programmatic Use

Block Parameter: TriggerType
Type: character vector
Values: 'rising' | 'falling' | 'either' | 'function-call' | 'message'
Default: 'rising'

Select this parameter to create a Simulink Function block by configuring a Subsystem block that is callable with arguments from a function caller. The Trigger block must reside within the subsystem. You can edit the function prototype that displays on the block face to specify input and output arguments for the block.

Clear this parameter to remove the configuration.

Dependencies

To display and enable this parameter, select function-call from the Trigger type list.

Programmatic Use

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

Specify whether to execute the Simulink Function block asynchronously for a subsystem containing this Trigger port block.

  • Select this check box to model asynchronous execution where the caller (client) makes a request to call the function (server). The function is executed based on the ordering defined in the Schedule Editor and then returns the output arguments to the caller.

  • Clear this check box to model synchronous execution where the caller calls the function and the function runs immediately then returns the output arguments to the caller.

Dependencies

To display and enable this parameter, from the Trigger type list, select function-call, then select the Treat as a Simulink Function parameter. Then, from the Function visibility list, select port.

Programmatic Use

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

Specify the function name for a Simulink Function block. Alternatively, you can specify the name by editing the function prototype on the face of the block.

f

Default name for a Simulink Function block.

function name

Function name that displays on the face of a Simulink Function block.

Dependencies

To display and enable this parameter, select function-call from the Trigger type list and select the Treat as a Simulink Function check box.

Programmatic Use

Block Parameter: FunctionName
Type: character vector
Values: 'f' | '<function name>'
Default: 'f'

Select scope of Simulink Function block within subsystem or model.

scoped

Limit accessibility of function to:

  • Hierarchic level containing the Simulink Function block and levels below.

  • One hierarchical level above with qualification.

global

Function accessible from any part of the model hierarchy.

port

Function accessible only through an exporting function port created by a Function Element block.

Dependencies

To display and enable this parameter, select function-call from the Trigger type list, then select the Treat as a Simulink Function check box.

Programmatic Use

Block Parameter: FunctionVisibility
Type: character vector
Values: 'scoped' | 'global' | 'port'
Default: 'scoped'

For a Simulink Function block with port visibility, specify the name of the exporting function port created by a Function Element block through which the function can be called.

Example: 'ServerPort'

Dependencies

To display and enable this parameter, from the Trigger type list, select function-call, then select the Treat as a Simulink Function check box. Then, from the Function visibility list, select port.

Programmatic Use

Block Parameter: ScopeName
Type: character vector
Values:'PortName'
Default: ''

Control activating the variant control (condition) defined with the Variant Control parameter.

Select this parameter to activate variant control of the subsystem. Selecting this parameter:

  • Enables the Variant control parameter.

  • Displays a variant badge on the face of the block indicating that variant conditions are enabled.

Clear this parameter to deactivate variant control of the subsystem.

Dependencies

To display and enable this parameter, select function-call from the Trigger type list and select the Treat as Simulink function check box.

Programmatic Use

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

Specify variant control (condition) expression that executes a variant Simulink Function block when the expression evaluates to true.

(inherit)

Default value for variant control. Inherits the variant condition from the corresponding Function Caller blocks in the model. When Variant Control is set as (inherit) the value for Generate preprocessor conditionals is inherited automatically from the Function Caller block in the model.

logical expression

A logical (Boolean) expression or a Simulink.Variant object representing a logical expression.

The function is activated when the expression evaluates to true.

If you want to generate code for your model, define the variables in the expression as Simulink.Parameter objects.

Dependencies

To display and enable this parameter, select function-call from the Trigger type list, select the Treat as a Simulink Function check box, then select the Enable variant condition check box.

Programmatic Use

Block Parameter: VariantControl
Type: character vector
Values: '(inherit)'|<logical expression> | Simulink.Variant object
Default: '(inherit)'

Control enclosing variant choices within C preprocessor conditional statements.

Select this parameter to enclose variant choices within C preprocessor conditional statements (#if) when generating code for an ERT target.

Dependencies

To display and enable this parameter, select the Enable variant condition check box.

Programmatic Use

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

Select how to set block state values when the subsystem or model is disabled.

held

Leave the block states at their current values.

reset

Reset the block state values.

inherit

Use the held or reset setting from the parent subsystem initiating the function-call. If the parent of the initiator is the model root, the inherited setting is held. If the trigger has multiple initiators, set the parents of all initiators to either held or reset.

Dependencies

To enable this parameter, select function-call from the Trigger Type list.

This parameter setting applies only if the model explicitly enables and disables the function-call subsystem. For example:

  • The function-call subsystem resides in an enabled subsystem. In this case, the model enables and disables the function-call subsystem along with the parent subsystem.

  • The function-call initiator that controls the function-call subsystem resides in an enabled subsystem. In this case, the model enables and disables the function-call subsystem along with the enabled subsystem containing the function-call initiator.

  • The function-call initiator is a Stateflow event bound to a particular state. See Control Function-Call Subsystems by Using bind Actions (Stateflow).

  • The function-call initiator is an S-function that explicitly enables and disables the function-call subsystem. See ssEnableSystemWithTid for an example.

Programmatic Use

Block Parameter: StatesWhenEnabling
Type: character vector
Values: 'held' | 'reset'| 'inherit'
Default: 'held'

Select when to propagate variable-size signals.

During execution

Propagate variable-size signals at each time step.

Only when enabling

Propagate variable-size signals when executing a Subsystem block or Model block containing an Enable port, Trigger port with Trigger type set to function-call, or Action Port block. When you select this option, sample time must be periodic.

Dependencies

To display and enable this parameter for a Trigger port block, select Function-call from the Trigger type list.

Programmatic Use

Block Parameter: PropagateVarSize
Type: character vector
Values: 'During execution' | 'Only when enabling'
Default: 'During execution'

Control display of an output port for a signal that identifies the trigger signal or function-call event signal.

Select this parameter to display the output port and determine which signal caused the trigger signal or function-call event. The width of the output port signal is the width of the control signal. The signal value is:

  • 1 for a signal that causes a rising trigger

  • -1 for a signal that causes a falling trigger

  • 2 for a function-call event

  • 0 in all other cases

Clear this parameter to remove the output port.

Dependencies

To display and enable this parameter, select an option other than message from the Trigger type list.

Programmatic Use

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

Select the output port data type for the signal that identifies the trigger signal or function-call event signal.

auto

Data type is the same as the port connected to the output.

double

Double value.

int8

Integer value

Dependencies

To enable this parameter, select the Show output port check box.

The Trigger block ignores the Data type override setting for the Fixed-Point Tool.

Programmatic Use

Block Parameter: OutputDataType
Type: character vector
Values: 'auto' | 'double' | 'int8'
Default: 'auto'

Select the calling rate for a subsystem or model.

triggered

Apply to applications that do not have a periodic function-call frequency. A function-call initiator can execute a triggered (aperiodic) function-call subsystem one or more times per time step and can provide a series of aperiodic function-call events.

periodic

A function-call initiator can execute a periodic function-call system only once per time step and must provide a series of periodic function-call events.. A Stateflow chart is an example of a function-call initiator.

Dependencies

To enable this parameter, select Function-call from the Trigger type list.

Programmatic Use

Block Parameter: SampleTimeType
Type: character vector
Values: 'triggered' | 'periodic'
Default: 'triggered'

Specify the time interval between function calls to a subsystem or model containing this Trigger port block. If the actual calling rate for the subsystem or model differs from the time interval this parameter specifies, Simulink® displays an error.

-1

Inherit time interval from the control signal.

Ts

Scalar where Ts is the time interval.

[Ts, To]

Vector where Ts is the time interval and To is the initial time offset.

Dependencies

To enable this parameter, select function-call from the Trigger type list and periodic from the Sample time type list.

Programmatic Use

Block Parameter: SampleTime
Type: character vector
Values: '-1' | 'Ts'| '[Ts, To]'
Default: '-1'

Select this parameter to detect zero crossings.

Dependencies

To enable this parameter, select rising, falling, or either from the Trigger type list.

Programmatic Use

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

Select the initial state of the trigger control signal.

compatibility (no trigger on first evaluation)

No trigger at the first evaluation of trigger signal. If you choose this option and the Trigger block is in a subsystem where the states are reset, the block does not reset.

zero

Zero. Helps to evaluate a rising or falling trigger signal at the first time step.

positive

Positive value. Helps to evaluate a falling trigger signal at the first time step.

negative

Negative value. Helps to evaluate a rising trigger signal at the first time step.

Dependencies

To display and activate this parameter, select rising, falling, or either from the Trigger type list.

Programmatic Use

Block Parameter: InitialTriggerSignalState
Type: character vector
Values: 'compatibility (no trigger on first evaluation)' | 'zero' | 'positive' | 'negative'
Default: 'compatibility (no trigger on first evaluation)'

For a subsystem triggered by message input, specify timing of execution.

on message available

Trigger execution of subsystem and pull messages whenever one or more messages are available at the control port.

on sample time hit

At each time step, check whether a message is available at the control port. If so, pull one message and trigger execution of subsystem. If no message is available, do not execute subsystem at that time step.

Dependencies

To display and activate this parameter, select message from the Trigger type list.

Programmatic Use

Block Parameter: TriggerTime
Type: character vector
Values: 'on message available' | 'on sample time hit'
Default: 'on message available'

For a subsystem triggered by message availability, specify execution mode.

Clear this check box for immediate mode, in which the subsystem executes as soon as a message is available at the control port, which pushes the message to the subsystem without a queue buffering the message.

Select this check box for scheduled mode, which allows subsystem execution to be deferred after a specific Simulink task while staying at the same time step.

Dependencies

To display and activate this parameter, select message from the Trigger type list, then select on message available from the Trigger time list.

Programmatic Use

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

Signal Attributes

Specify dimensions for the trigger signal attached externally a Model block and passed to the inside of the block.

1

Scalar signal.

[n]

Vector signal of width n.

[m n]

Matrix signal having m rows and n columns.

Dependencies

To display and enable this parameter for a Trigger port block at the root-level of a model, select rising, falling, or either from the Trigger type list.

Programmatic Use

Block Parameter: PortDimensions
Type: character vector
Values: '1' | '[n]' | '[m n]'
Default: '1'

Specify time interval between block method executions for the block driving the trigger signal.

-1

Inherit time interval.

Ts

Scalar where Ts is the time interval.

[Ts, To]

Vector where Ts is the time interval and To is the initial time offset.

Dependencies

To display and enable this parameter for a Trigger port block at the root-level of a model, select rising, falling, or either from the Trigger type list.

Programmatic Use

Block Parameter: TriggerSignalSampleTime
Type: character vector
Values: '-1' | 'Ts'| '[Ts, To]'
Default: '-1'

Specify minimum value for the trigger signal attached externally to a Model block and passed to the inside of the block.

Simulink uses this value to perform:

[]

Unspecified minimum value.

real scalar

Real scalar value.

Dependencies

To display and enable this parameter for a Trigger port block at the root-level of a model, select rising, falling, or either from the Trigger type list.

Programmatic Use

Block Parameter: OutMin
Type: character vector
Values: '[]' | '<real scalar>'
Default: '[]'

Specify maximum value for the trigger signal attached externally to a Model block and passed to the inside of the block.

Simulink uses this value to perform:

[]

Unspecified maximum value.

real scalar

Real scalar value.

Dependencies

To display and enable this parameter for a Trigger port block at the root-level of a model, select rising, falling, or either from the Trigger type list.

Programmatic Use

Block Parameter: OutMax
Type: character vector
Values: '[]' | '<real scalar>'
Default: '[]'

Select data type for the trigger signal attached externally to a Model block and passed to the inside of the block.

double

Double-precision floating point.

single

Single-precision floating point.

int8

Signed 8-bit integer.

uint8

Unsigned 8-bit integer.

int16

Signed 16-bit integer.

uint16

Unsigned 16-bit integer.

int32

Signed 32-bit integer.

uint32

Unsigned 32-bit integer.

int64

Signed 64-bit integer.

uint64

Unsigned 64-bit integer.

boolean

Boolean with a value of true or false.

fixdt(1,16)

Signed 16-bit fixed point number with binary point undefined.

fixdt(1,16,0)

Signed 16-bit fixed point number with binary point set to zero.

fixdt(1,16,2^,0)

Signed 16-bit fixed point number with slope set to 2^0 and bias set to 0.

<data type expression>

Data type object, for example Simulink.NumericType. You cannot enter the name of a Simulink.Bus object as a data type expression.

Dependencies

To display and enable this parameter for a Trigger port block at the root-level of a model, select rising, falling, or either from the Trigger type list.

Programmatic Use

Block Parameter: OutDataTypeStr
Type: character vector
Values: 'double' | 'single' | 'int8' | 'uint8' | 'int16' | 'uint16' | 'int32' | 'uint32' | 'int64' | 'uint64' | 'boolean' | 'fixdt(1,16)' | 'fixdt(1,16,0)' | 'fixdt(1,16,2^0,0)' | '<data type expression>'
Default: 'double'

Select data type category and display drop-down lists to help you define the data type.

Built in

Display drop-down lists for data type and Data type override.

Fixed point

Display drop-down lists for Signedness, Scaling, and Data type override.

Expression

Display text box for entering an expression.

Dependencies

To enable this parameter, select the Show data type assistant button .

Programmatic Use

No equivalent command-line parameter.

Control how missing workspace data is estimated when loading data from the MATLAB® workspace.

Select this parameter to linearly interpolate output at time steps for which no corresponding workspace data exists.

Clear this parameter to set the output at such time steps equal to the output at the most recent time step for which data exists.

Dependencies

To display and enable this parameter for a Trigger port block at the root-level of a model, select rising, falling, or either from the Trigger type list.

Programmatic Use

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

Block Characteristics

Data Types

Boolean | double | enumerated | fixed point | integer | single

Direct Feedthrough

no

Multidimensional Signals

yes

Variable-Size Signals

no

Zero-Crossing Detection

yes

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® 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

See Also

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