industrial//industrial communication//fieldbus

A fieldbus is one of the digital networks that connect controllers to field devices and were born before industrial Ethernet: serial buses such as Modbus on RS-485, PROFIBUS, and the automotive CAN bus.

A fieldbus is one of the digital networks that connect controllers to field devices and were born before industrial Ethernet: serial buses such as Modbus on RS-485, PROFIBUS, and the automotive CAN bus.

A digital device need not speak Ethernet: a fieldbus device is fully digital, addressed on a shared serial line, and has no IP address. Ethernet came later as another link under the same vocabularies (protocol stack, industrial Ethernet).

What a fieldbus defines is the conversation (who asks, what operation, which data); what it rides on (RS-485, CAN's differential pair) is defined by the physical standard. Modbus RTU and Modbus TCP are the same conversation on two different stacks.

It is the second rung of industrial communication, between the analog loop and industrial Ethernet, and shares its physics with the rest of serial electronics: differential signaling for noise and bus termination at both ends.

Fieldbuses are the layer a plant cannot throw away: a 2003 Modbus meter and a 2006 PROFIBUS DCS keep working for decades, and the digitalization job is to read them through a gateway rather than replace them (edge gateway).