Fairbanks FB2550 SERIES - Manual (Page 114)

Section 5: Input/ Output
07/2012 114 51254 Rev. 3
5.15. FIELDBUS CONNECTIONS
The term FIELDBUS usually describes an all-digital two-way communications
system that interconnects measurement and control equipment such as sensors,
actuators and controllers.
Fieldbus traces its beginnings in the automotive industry, where efforts to simplify
and reduce wiring resulted in a multiplexed CAN (Controller Area Network) system of
modules installed at various points of a vehicle.
A WORKING EXAMPLE
Most cars have multiple controls on the door panel, such as power-window, power-
mirror, power-lock and power-seat controls. A Fieldbus Network combines all the
switch wires into a two wire communication bus. Pressing a switch closes a relay
that provides power to the window motor, sending a packet of data onto the
communication bus to adjust the passenger-side mirror.
5.15.1. OVERVIEW OF TERMS
There are currently four (4) different types of
Fieldbus Interfaces listed as standard
accessories for the FB2550 Instrument.
•
DEVICE NET
– A network system to interconnect control
devices for data exchange.
– It uses a differential serial bus, called
Controller Area Network (CAN), as the backbone technology and defines an
application layer to cover a range of device profiles.
•
CONTROL NET
– An open control network in real-time, for high-throughput applications.
•
MODBUS
– Serial network communications in a master/slave (request/response) type
relationship using either ASCII or RTU (Remote Terminal Unit) modes.
•
PROFIBUS
– Non-powered two-wire (RS-485) network, with up to 126 nodes, transfering a
maximum of 244 data bytes per node per cycle.
NOTE: See Section 9.3.1. Installing the Fieldbus for complete connectivity
information.
Typical Fieldbus Card installation.