I/O subnets for the APS Control System

Although the Advanced Photon Source Control System allows for microprocessor-based input/output controllers (IOCs) to be distributed throughout the facility, it is not always cost-effective to provide such capability at every location where an interface to the control system is required. For greatest flexibility, the subnets must support connections to equipment that requires several discrete I/O points, connections to GPIB and RS232 instruments, and a network connection to custom designed intelligent equipment. An approach is described that supports all of these interfaces with one subnet implementation, BITBUS. In addition to accommodating several different interfaces on a single subnet, this approach also circumvents several limitations of GPIB and RS232 which would otherwise restrict their use in a harsh, industrial environment.<>