The enumerative type is special type that can be assigned to a sub-frame.
In the Enum dock is possible to define any number of enum groups and for each groups is possible to define up to 256 different enum values (it is an 8bit value). Each enum is defined by a pairs name-value.
For instance it is possible to define, in the enum group register, the list of registers that can be addressed by the set register frame, and for each register in the list the relative value to be set in sub-frame data.