The addressing of I / O-Modules (I / O) of a
Building Automation System shall be simplified. Therefore, there is provided a method of automatically addressing a plurality of I / O-Modules (I / O) of an I / O-Module arrangement being connected to a controller (BAC), the I / O-Modules (I / O) being arranged serially in a first I / O-
Bus segment (1) and at least a separate second I / O-
Bus segment, each I / O-
Bus segment (1, 2) including a
branch connection unit (BCC, BCN) and at least one of the I / O-Modules (I / O), the
branch connection units(BCC, BCN) of the first and second I / O-Bus segments (1, 2) are interconnected, the method includes the steps of providing pregiven topology data (engineered data) of the I / O-Module arrangement, the pregiven topology data includes for each I / O-Bus segment: a segment address and respective segment topology data, wherein the segment topology data includes an address of the controller or the respective
branch connection unit and each I / O-Module (I / O) of the respective I / O-Bus segment, automatically discovering physical segment topology data (
fingerprint) by the controller (BAC) in the first I / O-Bus segment (1) and by the respective branch connection module (BCC) in the second I / O-Bus segment (2) and automatically addressing all I / O-Modules with the respective segment address in accordance with the pregiven topology data, only if the physical segment topology data of each I / O-Bus segment (1, 2) corresponds to the respective segment topology data of the pregiven topology data.