Command input serves primarily for the secured switching of data points in Energy technology. 'Secured' means that there is a check whether the switching operation is allowed, according to the configured interlocking condition and the dynamically updated topology (no relation to the zenon network topology). The configuration of the topology is performed via the ALC.
These conditions determine whether the switching action is allowed at the moment (No interlocking condition is active), whether it is forbidden (non-unlockable condition is active) or whether it can be performed after unlocking (unlockable interlocking is active).
A data point of the command input always consists of 2 data points. The response variable and the command variable. The action is performed on one of these data points.
User actions are performed via a context menu or with the picture type 'Power'. Specific control elements are provided for this. This picture also contains a procedure which allows unlocking, two-step execution and locking. The picture can be activated via picture element, function or context menu.
The synchronization of the execution of the command input is performed via an access object which is runtime-monitored and updated cyclically in the driver and which is associated to the response variable. The activation of this object is indicated by the status 'Select' at the response variable.
The access objects are created on demand and associated with the creator on the RT side. Managing these objects in the driver makes sure that there is only one active access object per response variable.
The command interlockings can be exported and imported as well as exchanged and duplicated on the interlocking level. Command interlockings and general interlockings are stored in a common file (verriegel.bin/verrieg.cmp) and are also managed together. This is why it is not possible to have a general and a command interlocking with the same name.