DeviceNet & PROFIBUS: What Is the Difference?

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DeviceNet and Profibus -- short for Process Field Bus -- both serve as prominent digital networks for automation applications. Known as fieldbuses, these platforms connect field devices and their controllers via a single digital link rather than a series of point-to-point links. Although both act as general-purpose, device-level networks, DeviceNet focus on critical factory networking between industrial machines, while Profibus caters to quick, efficient communication between computers and programmable logic controllers, among other differences.

Functions

  • As a low-level network, DeviceNet connects industrial devices to high-level controllers. In contrast, Profibus accommodates high-level communication among devices. Unlike the real-time communication provided by DeviceNet, Profibus-networked devices don't communicate in real-time. DeviceNet focuses on interchangeability among simple devices such as switches, starters and sensors while Profibus generally caters to communication between controllers and peripherals, allowing high-speed data transfer between sensors and actuators. It acts chiefly as as master-slave network. Meanwhile, DeviceNet primarily serves as a peer-to-peer network.

Specifications

  • DeviceNet operates on the controller area network platform, a fast-response interconnect system that caters to industrial applications, and uses trunk- and drop-line topology, meaning it provides separate buses for signal and power distribution. It relies on thick and thin trunk- and drop-line cables, just like the twisted-pair, two-conductor copper wire cables of Profibus, which separates itself from DeviceNet via additional use of fiber optics.

    Networks connected by DeviceNet support up to 64 node addresses; Profibus supports 32 without repeaters or 127 with repeaters. Profibus supports a maximum distance of about 656 feet without repeaters or a half-mile with repeaters, while DeviceNet supports a maximum distance of about one-third mile.

Features

  • Via DeviceNet's distinct power distribution system, devices use one set of wires for both power and communication, typically eliminating the need for external power supplies for simple sensors. DeviceNet also allows you to remove devices and add power taps without removing network power. Features distinct to Profibus include the ability to operate as either a monomaster or multimaster system, including either independent subsystems or one master with assigned slaves.

Considerations

  • Although DeviceNet focuses on peer-to-peer networking, both platforms are capable of performing as master-slave type networks. DeviceNet provides asynchronous communication in contrast with the cyclical communication of Profibus. Both Allen-Bradley and Siemens -- the companies behind DeviceNet and Profibus, respectively -- offer detailed online knowledgebases, including communication sheets and data sheets for their fieldbuses.

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