The AS-i Master/Gateway controls the AS-i network and acts as a direct link to the host (PLC, Building Management Systems, etc.). Combined with an integrated mini-PLC functionality the master can also be used for pre-processing or as a stand-alone device without the need for a host controller (programming language IL or C).
A Gateway is an AS-i Master, and simultaneously a slave to higher level network (PROFIBUS, EtherNet/IP, Modbus, etc.). AS-Interface is the lowest level of the automation pyramid intended for Actuator/Sensor networking.
AS-i supports free topology such as Star, Ring, Linear, Tree and Mesh network (see examples below).