when I create some internal variables in zenon and activate them as externally visible, they are accessible in zenon logic. also the change of values affect both the zenon and zenon logic. but if I use external variables ,e.g from 60870-104 driver, and tick the externally visible option, they also are reachable in zenon logic, but changing the value from 104 device is not visible in zenon logic while I can see them in zenon!

what could make this difference?