Gateway for inter-network connection in the Pohang Light Source control system

The control system for the Pohang Light Source (PLS), under construction, is a large scale distributed computer control system which can manipulate approximately 7000 signals. It has a hierarchical structure with two heterogeneous data communication networks. The upper level network is a baseband Ethernet to link operator console computers with Subsystem Control Computers. The lower level network is a MIL-STD-1553B multidrop field bus which connects each Subsystem Control Computer with VME based local controllers. In this control system structure, frequent modification of local control software during system commissioning and maintenance periods requires repeated installations of developed software on the local controllers, which are distributed along the circumference of the storage ring. This paper describes the construction of a software gateway which is a specific kind of network server, to interconnect the two different networks so that an operator in the upper level network is able to access any low level local control computer transparently