MATLAB: How to set a change event (Implicit Event in Stateflow) to get triggered only when the value of a variable changes to a different one

Question

How can I set a change event (Implicit Event in Stateflow) to get triggered only when the value of a variable changes to a different one? Right now it gets triggered everytime the variable gets written to, even when the value remains the same.

Answer 1

You can use the hasChanged operator, which was introduced in Stateflow 7.0 (R2007b). If you are using a previous version, you would need to create a top-level parallel state which double buffers the data values and the actual check would be transformed to:

"data_prev != data_start"

The top-level parallel state would need to contain something like the following:

data_prev = data_start;
data_start = data;