Fieldbus connections, Overview of terms – Fairbanks FB2550 DAT SERIES DRIVER ACCESS TERMINAL User Manual
Page 89

Section 4: Input/ Output
2/2013
89
51303 Rev. 1
5.8. 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.
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.
5.8.1. OVERVIEW
OF
TERMS
There are currently four (4) different types of
Fieldbus Interfaces
listed as standard
accessories for the FB2550 DAT.
DEVICENET –
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.
CONTROLNET –
An open Control Network in real-time, for high-throughput
applications.
MODBUS-TCP–
Serial network communications in a master/slave
(request/response) type relationship using either ASCII or RTU (Remote Terminal
Unit) modes.
– 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.