trigger a transition with a condition

I have my variable (a) loaded into a data store via a constant outside of the stateflow to be equal to 0. Then inside the initial simulink state, I update the data store of a to equal 1 (constant block Connected to data store write). The transition has a condition [a==1]. The symbol is tied to data store and says it’s becomes equal to one, but the transition never triggers. I can hover over the condition and it tells me a=1, but does not trigger. I’ve set the initial constant to 1, and the transition triggers.

Answer 1

[Akanksha]

Hi Rebecca Red,

Basically, in Simulink and Stateflow, the order of execution plays a vital role. When you update your variable “a” using a "Data Store Write" block connected to a constant, the new value of “a” (in your case, 1) might not be available to Stateflow in the same simulation step when the transition condition [a==1] is evaluated. This is why the transition doesn’t trigger unless you set the initial value to 1.

To ensure that Stateflow sees the updated value ofabefore evaluating the transition, you can:

1. Check Execution Order: Make sure the Data Store Write operation happens before the Stateflow chart executes. You can control this using theBlock Execution Orderby setting priorities or using function calls.
2. Use Data Store Memory Properly: Ensure that your Data Store Memory, Data Store Write, and Stateflow chart are all referencing the same variable and that the data store is accessible to the chart.
3. Consider Direct Signals: If possible, instead of using a Data Store, directly connect the signal to the Stateflow chart as an input. This often leads to more predictable behavior.

Suppose you have:

• A Constant block (value = 1)
• A Data Store Write block (writes to“a”)
• A Stateflow Chart (usesafor transition)

You can set the execution order so that the Data Store Write happens before the chart:

% In the model, right-click the blocks and set their priorities: 
set_param('yourModel/YourDataStoreWriteBlock','Priority','1') 
set_param('yourModel/YourStateflowChart','Priority','2') 

This ensures the value is written before the chart checks the transition.

Below are some helpful official links for your reference :

• https://www.mathworks.com/help/simulink/slref/datastorememory.html describes how to create and configure a shared memory location (the data store) that multiple blocks including Data Store Write and Stateflow charts can access.
• https://www.mathworks.com/help/simulink/slref/datastorewrite.html will help you to write values to a data store during simulation.

Hope this helps!