From Control Studio online or debug you can enter any writeable function block parameter in the fieldbus device. The mechanism for the update of the value in the device is the same as described above. Device-sourced function blocks that appear in control module function block diagrams are really controller-resident extended blocks. Any writeable parameter can be changed in the extended block, but some parameters require that the target mode be OOS (Out of Service) in order for the update in the device to be successful.