To avoid common design errors, you can run diagnostic checks that test the completeness of your Stateflow® chart during compilation and simulation. Stateflow diagnostics detect state inconsistencies, violations in data ranges, and cyclic behavior in Stateflow charts in Simulink® models.
When you simulate a model, the Stateflow parser evaluates the graphical and nongraphical objects and data in each Stateflow machine against the supported chart notation and the action language syntax. You can also check the syntax of your chart by selecting Update Chart in the Modeling tab of the Stateflow Toolstrip.
If syntax errors exist in your chart, the chart automatically appears with the highlighted object that causes the first error. You can select the error in the diagnostic window to bring its source chart to the front with the source object highlighted. Any unresolved data or events in the chart are flagged in the Symbol Wizard.
In a Stateflow chart, states are inconsistent if they violate one of these rules:
An active state with exclusive (OR) decomposition and at least one substate has exactly one active substate.
All substates of an active state with parallel (AND) decomposition are active.
All substates of an inactive state are inactive regardless of the state decomposition.
While you edit your chart, the Stateflow Editor displays potential causes for state inconsistencies by highlighting objects in red or orange. For more information, see Detect Modeling Errors During Edit Time.
One type of state inconsistency occurs when all of these conditions are true:
A state with multiple substates has exclusive (OR) decomposition.
The state does not contain a history junction.
Every default path that leads to a substate is guarded by a condition or triggered by an event.
Not all transitions into the state are supertransitions leading directly to a substate.
For example, this chart has a state inconsistency because there is no default transition to indicate which substate becomes active first.
Adding an unconditional default transition to one of the states resolves the state inconsistency.
At compile time, Stateflow charts detect state inconsistencies caused by the omission of an
unconditional default transition. To control the level of diagnostic action, open the
Model Configuration Parameters dialog box. In the Diagnostics > Stateflow pane, for the diagnostic No unconditional default
transitions, you can select
none. The default
error. For more information, see No unconditional default transitions (Simulink).
During simulation, a data range violation occurs when:
For example, this chart contains local data
a that has a
Minimum value of 0 and a Maximum value of 2. The
entry action in state
a to 1. The
during action increments the value of
a by 1. After two time steps, the value of
its specified range, resulting in a data range violation.
At run time, Stateflow charts detect data range violations. To control the level of diagnostic
action, open the Model Configuration Parameters dialog box. In the Diagnostics > Data Validity pane, you can select
none for these diagnostics:
Simulation range checking detects violations based on
minimum-and-maximum range checks. The default setting is
Wrap on overflow and Saturate on
overflow detect violations that occur when integer or fixed-point
operations exceed the numeric capacity of their result type. The default setting is
Cyclic behavior occurs when a step or sequence of steps is repeated indefinitely during chart simulation.
For example, the actions in this chart produce an infinite cycle of recursive event broadcasts.
during action in state
C broadcasts the
E1 triggers the transition from state
A.A1 to state
A.A2. The condition action for
this transition broadcasts the event
E2 triggers the transition from state
B.B1 to state
B.B2. The condition action for
this transition broadcasts the event
The event broadcasts in states
occur in condition actions, so the transitions do not take place until the chart processes
the resulting events. The substates
remain active, so new event broadcasts continue to trigger the transitions and the process
Because undirected local event broadcasts can cause unwanted recursive behavior, use of
send operator to broadcast
directed local events is recommended. For more information, see Broadcast Local Events to Synchronize Parallel States.
During chart simulation, Stateflow charts use cycle detection algorithms to detect a class of infinite recursions caused by event broadcasts. To enable cycle detection, open your Stateflow chart. In the Debug tab, select Diagnostics > Detect Cyclical Behavior. Cyclic behavior checking is selected by default.
Stateflow charts also detect undirected local event broadcasts. To control the level
of diagnostic action, open the Model Configuration Parameters dialog box. In the Diagnostics > Stateflow pane, for the Undirected event broadcasts diagnostic,
you can select
none. The default setting is
warning. For more information, see Undirected event broadcasts (Simulink).
Stateflow cycle detection is limited to cases of recursion due to event broadcasts and does not extend to other types of cyclic behavior.
For instance, Stateflow cannot detect the infinite cycle in this flow chart. In this example, the
default transition initializes the local data
i to 0. The next
transition segment increments
i. The transition to the terminating
junction is valid only when the condition
[i < 0] is true. Because
this condition is never true, an infinite cycle results.
sf_cycle_error_fix provides suggestions for fixing cyclic behavior
in flow charts. At the MATLAB® command prompt,