Chart

Implement control logic with finite state machine

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Libraries:
Stateflow

Description

The Chart block graphically represents a finite state machine. In a Stateflow^® chart, states and transitions form the basic building blocks of a sequential modal logic system. States correspond to operating modes and transitions represents the passage of the system from one operating mode to another. For more information, see Model Finite State Machines by Using Stateflow Charts.

To implement control logic, Stateflow charts can use MATLAB^® or C as the action language. For more information, see Differences Between MATLAB and C as Action Language Syntax.

Examples

Simplify Stateflow Charts by Incorporating Active State Output

Active state data can simplify the design of some Stateflow® charts because you do not have to maintain data that is highly correlated to the chart hierarchy. When you enable active state data, Stateflow reports state activity through an output port to Simulink® or as local data in your chart. This example shows how to simplify the design of a Stateflow chart by adding active state output data. For more information, see Monitor State Activity Through Active State Data.

• Open Model

Model a Fitness Tracker

Implement a fitness tracker by using temporal logic and messages.

• Open Model

Ports

Input

Port_1 — Input port

scalar | vector | matrix

When you create input data in the Stateflow chart using the Symbols pane, Stateflow creates a corresponding input port on the Chart block.

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

Output

Port_1 — Output port

scalar | vector | matrix

When you create output data in the Stateflow chart by using the Symbols pane, Stateflow creates a corresponding output port on the Chart block.

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

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.

Note

Charts also have Subsystem (Simulink) block parameters that you can access by right-clicking the chart and clicking Block Parameters (Subsystem). However, updating these parameters is not recommended.

Update method — Method to update or wake up Stateflow charts

Inherited (default) | Discrete | Continuous

Method to update or wake up a Stateflow chart, specified as Inherited, Discrete, or Continuous.

Inherited

Input from the Simulink model determines when the chart wakes up during a simulation.

If you define input events for the chart, the signal from the Simulink block connected to the trigger port triggers the chart. The Simulink signal can be Rising, Falling, or Either (rising and falling), or in response to a Function Call. For more information, see Activate a Stateflow Chart by Sending Input Events.

If you do not define input events, the Stateflow chart implicitly inherits triggers from the Simulink model. These implicit events are the discrete or continuous sample times of the Simulink signals that provide inputs to the chart. If you define data inputs, the chart wakes at the rate of the fastest data input. If you do not define any data input for the chart, the chart wakes up as defined by the execution behavior of its parent subsystem.

Discrete

The Stateflow chart wakes when the Simulink model generates an implicit event at regular time intervals that you specify in the Sample Time chart property. Other blocks in the Simulink model can have different sample times.

Continuous

The Stateflow chart updates its state during major time steps only, and computes outputs and local continuous variables during major and minor time steps. The chart can register zero crossings, which allows Simulink models to sample Stateflow charts whenever state changes occur. The Stateflow chart computes derivatives for local continuous variables. For more information, see Continuous-Time Modeling in Stateflow.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	ChartUpdate
Values:	"INHERITED" (default) | "CONTINUOUS" | "DISCRETE"

Sample Time — Time interval that a Stateflow chart wakes up during simulation

-1 (default) | scalar | vector

Specify the time interval at which the chart wakes up during simulation. The default value indicates that the chart inherits the sample time from Simulink. For more information on specifying sample time, see Specify Sample Time (Simulink).

Do not use the Sample Time parameter in the Subsystem block parameters. Instead, use the Property Inspector.

Dependencies

To enable this parameter, set Update method to Discrete.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	SampleTime
Values:	"-1" (default) | string scalar | character vector
Data Types:	string | char

Enable zero-crossing detection — Whether to enable zero-crossing detection on state transitions in the chart

on (default) | off

Whether to enable zero-crossing detection on state transitions in the chart. For more information, see Continuous-Time Modeling in Stateflow.

Dependencies

To enable this parameter, set Update method to Continuous.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	EnableZeroCrossings
Values:	true or 1 (default) | false or 0
Data Types:	logical

Enable C-bit operations — Whether to enable C-bit operations in the chart

off (default) | on

Whether to use bit operations in state and transition actions in the chart, specified as a numeric or logical 1 (true) or 0 (false).

Dependencies

To enable this parameter, set Action language to C.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	EnableBitOps
Values:	false or 0 (default) | true or 1
Data Types:	logical

Create output for monitoring — Whether to create active state data output

off (default) | on

Whether to create an active state data output port for the chart. For more information, see Monitor State Activity Through Active State Data.

Dependencies

To enable this parameter, create a Stateflow state, state transition table, or atomic subchart.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	HasOutputData
Values:	false or 0 (default) | true or 1
Data Types:	logical

Output monitoring mode — Monitoring mode for active state output

Child activity (default) | Leaf state activity

Monitoring mode for the active state output data. For more information, see Monitor State Activity Through Active State Data.

Dependencies

To enable this parameter, enable Create output for monitoring.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	OutputMonitoringMode
Values:	"ChildActivity" (default) | "LeafStateActivity"

Data name — Name of active state data object

ChartMode | scalar

Name of the active state data object for the state transition table.

Dependencies

To enable this parameter, enable Create output for monitoring.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	OutputPortName
Values:	"ChartMode" (default) | string scalar | character vector
Data Types:	string | char

Enum name — Name of enumerated data type for active state data object

ChartModeType | scalar

Name of the active state data object for the state transition table.

Dependencies

To enable this parameter, enable Create output for monitoring.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	EnumTypeName
Values:	"ChartModeType" (default) | string scalar | character vector
Data Types:	string | char

Define enumerated type manually — Whether to define enumerated data type manually

off (default) | on

Whether to define the enumerated data type for the active state data output manually90. For more information, see Define State Activity Enumeration Type.

Dependencies

To enable this parameter, enable Create output for monitoring.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	DoNotAutogenerateEnum
Values:	false or 0 (default) | true or 1
Data Types:	logical

Advanced

Execute (enter) chart at initialization — Whether to initialize state configuration

off (default) | on

Whether to initialize the state configuration of the chart at time zero instead of at the first input event. For more information, see Execution of a Chart at Initialization.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	ExecuteAtInitialization
Values:	false or 0 (default) | true or 1
Data Types:	logical

Saturate on integer overflow — Whether data saturates on integer overflow

on (default) | off

Whether the data in the chart saturates on integer overflow. When you clear this parameter, the data in the chart wraps on integer overflow. For more information, see Handle Integer and Enumeration Overflow for Chart Data.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	SaturateOnIntegerOverflow
Values:	true or 1 (default) | false or 0
Data Types:	logical

Initialize outputs every time chart wakes up — Whether to initialize output data

on (default) | off

Whether to initialize the output data every time the chart wakes up.

When you select this parameter, the chart resets its output values every time that the chart wakes up, not only at time 0. The chart resets the output values whenever function call, edge trigger, or clock tick triggers the chart. If you set an initial value for an output data object, the output resets to that value. Otherwise, the output resets to zero. Select this parameter to:

• Ensure that all outputs are defined in every chart execution.

• Prevent latching of outputs, that is, prevent values of outputs computed in previous executions.

• Provide all chart outputs with a meaningful initial value.

For more information, see Initial value.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	InitializeOutput
Values:	true or 1 (default) | false or 0
Data Types:	logical

Support variable-size arrays — Whether the chart supports variable size data

on (default) | off

Whether the chart supports variable-size data. For more information, see Declare Variable-Size Data in Stateflow Charts.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	SupportVariableSizing
Values:	true or 1 (default) | false or 0
Data Types:	logical

Export chart level functions — Whether to export chart-level functions

off (default) | on

Whether to export chart-level functions to other blocks in the Simulink model. For more information, see Export Stateflow Functions for Reuse.

Dependencies

To enable this parameter, add a function to your chart.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	ExportChartFunctions
Values:	false or 0 (default) | true or 1
Data Types:	logical

Treat exported functions as globally visable — Whether exported functions are globally visible

off (default) | on

Whether exported functions from the chart are globally visible in the Simulink model. When this property is enabled, blocks throughout the model can call functions exported from the chart without using qualified notation.

Dependencies

To enable this parameter, enable Export chart level functions.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	AllowGlobalAccessToExportedFunctions
Values:	false or 0 (default) | true or 1
Data Types:	logical

Enable super step semantics — Whether to enable super step semantics

off (default) | on

Whether to enable super step semantics for the chart. Select this parameter to enable the chart to take multiple transitions in each time step until it reaches a stable state. This option is not available when you. For more information, see Super Step Semantics.

Dependencies

To enable this parameter, set Update method to Discrete.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	EnableNonTerminalStates
Values:	false or 0 (default) | true or 1
Data Types:	logical

Max iterations in a superstep — Maximum number of transitions

1000 (default) | positive integer

The maximum number of transitions that can be completed in one super step. For more information, see Super Step Semantics.

Dependencies

To enable this parameter, enable Enable super step semantics.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	NonTerminalMaxCounts
Values:	1000 (default) | positive integer
Data Types:	single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

After too many iterations — Action if super step exceeds maximum number of transitions

Proceed (default) | Throw Error

Action for Stateflow to take if super step exceeds maximum number of transitions in one super step. For more information, see Super Step Semantics.

Dependencies

To enable this parameter, enable Enable super step semantics.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	NonTerminalUnstableBehavior
Values:	"Proceed" (default) | "Throw Error"

Treat dimensions of length 1 as fixed size — Whether chart treats output data with dimension of length 1 as fixed size

on (default) | off

Since R2022b

Whether the chart treats output data with a dimension of length 1 as fixed size. When you select this parameter, the chart treats output data that have at least one dimension of length 1 as fixed size, regardless of whether you enable the Variable size data property. When you clear this parameter, the chart treats data with the Variable size property enabled as variable size.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	TreatDimensionOfLengthOneAsFixedSize
Values:	true or 1 (default) | false or 0
Data Types:	logical

Variant activation time — Active choice of the variant blocks or variant parameters at different stages of the simulation and code generation workflow

update diagram analyze all choices (default) | code compile

Specify which block variants Stateflow analyzes during simulation and code generation. Based on the option you choose, Stateflow determines if the generated code must contain only the active choice or both active and inactive choices.

• update diagram analyze all choices — When you select this option, Stateflow analyzes both active and inactive choices for incompatibilities in signal attributes and generates code only for the active choice.

• code compile — When you select this option, Stateflow analyzes both active and inactive choices of variant transitions and generates code for both the active and inactive choices. The choices are enclosed in C preprocessor conditional statements #if and #endif that are conditionally compiled when you compile the generated code.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	VariantActivationTime
Values:	"update diagram analyze all choices" (default) | "code compile"

Action language — Action language

MATLAB (default) | C

Action language to use to program the chart, specified as MATLAB or C. For more information, see Differences Between MATLAB and C as Action Language Syntax.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	ActionLanguage
Values:	"MATLAB" (default) | "C"

State machine type — State machine semantics

Classic (default) | Mealy | Moore

State machine semantics implemented by the chart, specified as Classic, Mealy, or Moore. For more information, see Overview of Mealy and Moore Machines.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	StateMachineType
Values:	"Classic" (default) | "Mealy" | "Moore"

Fixed-point properties

Treat these inherited Simulink signal types as fi objects — Inherited Simulink signals to treat as fi objects

Fixed-point (default) | Fixed-point & Integer

Inherited Simulink signals to treat as Fixed-Point Designer™ fi objects, specified as one of these values:

• Fixed-point — The chart treats all fixed-point inputs as fi objects.

• Fixed-point & Integer — The chart treats all fixed-point and integer inputs as fi objects.

Dependencies

To enable this parameter, set Action language to MATLAB.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	TreatAsFi
Values:	"Fixed-point" (default) | "Fixed-point & Integer"

MATLAB Chart fimath — Default fimath properties

Same as MATLAB (default) | Specify Other

Default fimath properties for the chart, specified as one of these values:

• Same as MATLAB — The chart uses the same fimath object properties as the current default fimath object. The text box is dimmed and displays the current global fimath object in read-only form.

• Specify other — Specify your own fimath object in the text box one of two ways:

  • Constructing the fimath object inside the text box.

  • Constructing the fimath object in the MATLAB or model workspace and then entering its variable name in the text box. If you use this option and plan to share your model with others, define the variable in the model workspace.

For more information, see fimath Object Construction (Fixed-Point Designer).

Dependencies

To enable this parameter, set Action language to MATLAB.

Programmatic Use

To set the chart parameter value programmatically, access the Stateflow.Chart object of the chart and change the object property by using dot notation.

Parameter:	EmlDefaultFimath
Values:	"Same as MATLAB Default" (default) | "Other:UserSpecified"

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 additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has one default HDL architecture.

Active State Output

To generate an output port in the HDL code that shows the active state, in the Properties window of the chart, select Create output for monitoring. The output is an enumerated data type. See Simplify Stateflow Charts by Incorporating Active State Output.

Registered Output

To insert an output register that delays the chart output by a simulation cycle, use the OutputPipeline (HDL Coder) block property.

HDL Block Properties

ClockDrivenOutput	Enable clock-driven outputs to prevent combinatorial logic from driving the output and to allow an immediate output update when the clock signal and state change. The default is off. When you set ClockDrivenOutput to on, HDL Coder adds an output register that updates when the state updates. The final output variable is then assigned a value from the clock-drive register. This option is available only for Moore charts.
ConstMultiplierOptimization	Canonical signed digit (CSD) or factored CSD optimization. The default is none. See also ConstMultiplierOptimization (HDL Coder).
ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
DistributedPipelining	Pipeline register distribution, or register retiming. The default is inherit. See also DistributedPipelining (HDL Coder).
GuardIndexVariables	Specify whether to hoist array indices out of conditional statements or not. When you enable certain optimizations such as RAM Mapping, loop streaming, sharing, and so on, expressions are moved out of the array indices. A temporary variable is created for the expression that might result in an index out-of- bounds error during simulation. The default is off. See GuardIndexVariables (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 is 0. For more details, see InputPipeline (HDL Coder).
InstantiateFunctions	Generate a VHDL® entity or Verilog® module for each function. The default is off. See also InstantiateFunctions (HDL Coder).
LoopOptimization	Unroll, stream, or do not optimize loops. The default is none. See also LoopOptimization (HDL Coder).
MapPersistentVarsToRAM	Map persistent arrays to RAM. The default is off. See also MapPersistentVarsToRAM (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 is 0. For more details, see OutputPipeline (HDL Coder).
ResetType	Suppress reset logic generation. The default is default, which generates reset logic. See also ResetType (HDL Coder).
SharingFactor	Number of functionally equivalent resources to map to a single shared resource. The default is 0. See also Resource Sharing (HDL Coder).

Optimizations

The block participates in these HDL optimizations to optimize the speed, and area.

Speed and Area Optimization

Optimization	Description
Distributed Pipelining (HDL Coder)	Distributed pipelining, or register retiming, is a speed optimization that moves existing delays in a design to reduce the critical path while preserving functional behavior.
Resource Sharing (HDL Coder)	Resource sharing is an area optimization in which HDL Coder identifies multiple functionally equivalent resources and replaces them with a single resource.
Delay Balancing (HDL Coder)	When optimizations or block implementation options introduce delays along the critical path in a model, Delay Balancing detects introduction of new delays along one path, and then inserts matching delays on the other paths.
Clock-Rate Pipelining (HDL Coder)	Clock-rate pipelining is an optimization framework in HDL Coder that allows other speed and area optimizations to introduce latency at the clock rate.
Adaptive Pipelining (HDL Coder)	Adaptive pipelining optimization creates patterns or combination of blocks with registers that can improve the achievable clock frequency and reduce the area usage on the FPGA boards by inserting pipeline registers to the blocks in your design.
Critical Path Estimation (HDL Coder)	To quickly identify the most likely critical path in your design, use Critical Path Estimation. Critical path estimation speeds up the iterative process of finding the critical path. To know blocks that are characterized in critical path estimation, see Characterized Blocks (HDL Coder).

Complex Data Support

This block supports code generation for complex signals.

Restrictions

To learn about restrictions of using charts, see Introduction to Stateflow HDL Code Generation (HDL Coder).

When you apply optimizations, the block has these limitations:

• Stateflow Chart that has State Machine Type property set to Moore does not support HDL optimizations.

• HDL optimizations are not supported for the Stateflow Chart that has Trigger port.

PLC Code Generation

Generate Structured Text code using Simulink® PLC Coder™.

PLC Block properties

UseExternalDefinition

Suppress block definition in generated code. The default is Off. See also UseExternalDefinition (Simulink PLC Coder).

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced before R2006a

R2024a: Implicit ordering of transitions and parallel states will be removed

In a future release, the property User-specified state/transition execution order will be removed. This property applies only to charts that use C as the action language.

• When you enable this property, charts execute transitions and parallel states in the order you created them. You can also manually determine the execution order.

• When you disable this property, charts execute transitions and parallel states according to an implicit order defined by physical position.

  Transitions execute according to:

  1. The hierarchical level of the parent of each transition.

  2. The labels of the transition, in this order:

     1. Labels with events and conditions.

     2. Labels with events.

     3. Labels with conditions.

     4. No label.

  3. The angular surface position of the transition source. The transition with the smallest clock position has the highest priority. For example, a transition with a 2 o'clock position has a higher priority than a transition with a 4 o'clock position. A transition with a 12 o'clock source position has the lowest priority.

  Parallel states execute in this order:

  1. Top to bottom.

  2. Left to right.

To ensure your implicitly ordered charts remain compatible, enable the User-specified state/transition execution order property.

R2023b: Convert to state transition table

To convert a chart to a state transition table, use the function convertToSTT.

R2023a: Specify how to treat output data with dimension of length 1

With the new property Treat dimensions of length 1 as fixed size, you can specify how charts treat output data when at least one dimension has length 1. Prior to R2023a, charts treat output data with at least one dimension of length 1 as fixed size, regardless of whether you enable the Variable size data property.