Bus monitor unit

A central node for a data bus system includes a bus monitor unit with receiver means for registering signals on the data bus, and evaluation means which detect incorrect communication on the data bus and at least temporarily block communication by the user that causes the incorrect communication or compensate the incorrect communication of a user which is triggered by the interference influences. The bus monitor unit includes timing means which are triggered according to time patterns for the transmission of each user of the data bus, in order to detect an incorrect communication of a user if the latter transmits outside the time provided for it. The bus monitor unit is integrated into the central bus node and a plurality of bus branches of different users are combined at the central node so that the bus monitor unit can check a plurality of users for incorrect communication. In order to increase reliability, in addition to the bus monitor unit, a diagnostic unit is integrated into the central node. The latter monitors the bus monitor unit in terms of regular retriggering in response to the time patterns, so that the bus monitor unit can be deactivated in the absence of retriggering.