industrial//fieldbus

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

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

"Digital" never meant "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.

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).