How to make a Simulink block constant, execute only once?

I have a model in Simulink (2018a) which has more models inside. So I have:

    parent.slx --> child.slx

I want child.slx to execute only once in the whole simulation, so basically its output will be constant at all times.

Answer 1

[TAB]

Put your child model in Enabled Subsystem in parent model.

[parent.slx [Enabled Subsystem [Enchild.slx]]]

Enable the subsystem only once using "Stateflow" or using "Constant block + Unit delay Block arrangement".

Using "Constant block + Unit delay Block arrangement" you can do as below

[Constant(Value=0)]-->[Unit delay (Initial condition=1)]--> to enable port