How to set Smartfield as Valuehelp only property using cds annotations

I have a requirement where i need to change the smartfield which is an Input field to F4 help field and make the field allow to choose values from F4 only in a std fiori element object page app. I am able to make the field as F4 by creating annotate extension view in backend. But i am not able to restrict manual input into the field.

Kindly suggest.