12 - Open industrial Fieldbus and DeviceNet systems

Abstract

This chapter examines different open industrial Fieldbus and DeviceNet systems in the market. Fieldbus and DeviceNet are communications standards that enable communications between smart or intelligent instruments, and a master device such as a PLC. DeviceNet generally refers to the on/off and simpler digital devices whilst Fieldbus tends to encompass instrumentation systems, which need to transfer 16-bit data as a minimum. Very simple field devices such as proximity switches, limit switches, and basic actuators only require a few bits of digital information to communicate an “off” or “on” state. These are usually associated with real time control applications where an update time of a few milliseconds is required. There are real benefits to be gained from the emerging Fieidbus networks, including reduced wiring costs, reduced installation and startup time, improved on-line monitoring and diagnostics, easy change-out and expansion of devices, improved local intelligence in the devices, and improved interoperability between manufacturers. This chapter describes the origin and benefits of Fieldbus and DeviceNet systems, and lists three network classes of Fieldbus and DeviceNet systems. The chapter also describes the characteristics of some of the standards, including actuator sensor interface (AS-i), Seriplex, CANbus and DeviceNet, Interbus-S, Profibus, Factory information bus (FIP) and WorldFIP, and Foundation Fieldbus.