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.

Using Message Polling and Message Triggered Subsystems

Using Message Polling and Message Triggered Subsystems

Demonstrate and compare Message Triggered Subsystems and Message Polling Subsystems.

Model Reference Function-Call

Model Reference Function-Call

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

Set Priority in Execution Order of Blocks

Set Priority in Execution Order of Blocks

Set block priority to change execution order during simulation.

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®.

Model Engine Timing Using Triggered Subsystems

Model Engine Timing Using Triggered Subsystems

Model a four-cylinder spark ignition internal combustion engine from the throttle to the crankshaft output using triggered subsystems. In this example, the sldemo_engine model is based on [1].

Engine Timing Model with Closed Loop Control

Engine Timing Model with Closed Loop Control

Develop and implement a closed loop control algorithm for the open loop engine model described in Model Engine Timing Using Triggered Subsystems. In this example, the model sldemo_enginewc contains a controller that regulates engine speed using a fast throttle actuator such that changes in load torque have minimal effect. The controller is implemented using a discrete PI controller.

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 set Trigger type to message.

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. The block must be 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, set Trigger type to function-call.

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 parameter 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 parameter 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, set Trigger type to function-call, select Treat as a Simulink Function, and set Function visibility to 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.

Dependencies

To display and enable this parameter, set Trigger type to function-call and select Treat as a Simulink Function.

Programmatic Use

Block Parameter: FunctionName
Type: character vector
Values: 'f' | function name in quotes
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, set Trigger type to function-call and select Treat as a Simulink Function.

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, set Trigger type to function-call, select Treat as a Simulink Function, and set Function visibility to port.

Programmatic Use

Block Parameter: ScopeName
Type: character vector
Values: port name in quotes
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, set Trigger type to function-call and select Treat as Simulink function.

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.VariantExpression 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, set Trigger type to function-call, select Treat as a Simulink Function, and select Enable variant condition.

Programmatic Use

Block Parameter: VariantControl
Type: character vector
Values: '(inherit)' | logical expression | Simulink.VariantExpression 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 Enable variant condition .

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, set Trigger Type to function-call.

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, set Trigger type to Function-call.

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, set Trigger type to an option other than message.

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 from the port connected to the output

  • double — Double value

  • int8 — Integer value

Dependencies

To enable this parameter, select Show output port.

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, set Trigger type to Function-call.

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, the software displays an error.

  • Ts — Scalar where Ts is the time interval

  • [Ts, To] — Vector where Ts is the time interval and To is the initial time offset

  • -1 — Inherited time interval from the control signal

Dependencies

To enable this parameter, set Trigger type to function-call and Sample time type to periodic.

Programmatic Use

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

Select this parameter to detect zero crossings.

Dependencies

To enable this parameter, set Trigger type to rising, falling, or either.

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, set Trigger type to rising, falling, or either.

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, set Trigger type to message.

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 parameter 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 parameter 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, set Trigger type to message and Trigger time to on message available.

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 into the referenced model.

  • 1 — Scalar signal

  • [n] — Vector signal of width n

  • [m n] — Matrix signal having m rows and n columns

  • -1 — Inherited dimensions

Dependencies

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

Programmatic Use

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

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

  • -1 — Inherited 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, set Trigger type to rising, falling, or either.

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.

The software uses this value to perform:

Dependencies

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

Programmatic Use

Block Parameter: OutMin
Type: character vector
Values: '[]' | real scalar in quotes
Default: '[]'

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

The software uses this value to perform:

Dependencies

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

Programmatic Use

Block Parameter: OutMax
Type: character vector
Values: '[]' | real scalar in quotes
Default: '[]'

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

  • Inherit: auto — Inherited data type

  • 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 a Simulink.NumericType object

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, set Trigger type to rising, falling, or either.

Programmatic Use

Block Parameter: OutDataTypeStr
Type: character vector
Values: 'Inherit: auto' | '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: 'Inherit: auto'

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

  • Built in — Display menus for data type and Data type override.

  • Fixed point — Display menus 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 .

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, set Trigger type to rising, falling, or either.

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

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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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