Broadcom

AV02-0876EN

12

HCPL-0720, HCPL-7720, HCPL-0721,

and HCPL-7721 Data Sheet

40-ns Propagation Delay, CMOS Optocoupler

Digital Field Bus Communication Networks

To date, despite its many drawbacks, the 4 mA to 20 mA analog current loop has been the most widely accepted standard

for implementing process control systems. In today’s manufacturing environment, however, automated systems are

expected to help manage the process, not merely monitor it. With the advent of digital field bus communication networks

such as CC-Link, DeviceNet, PROFIBUS, and Smart Distributed Systems (SDS), gone are the days of constrained

information. Controllers can now receive multiple readings from field devices (sensors, actuators, etc.) in addition to

diagnostic information.

The physical model for each of these digital field bus communication networks is very similar as shown in Figure 11. Each

includes one or more buses, an interface unit, optical isolation, transceiver, and sensing and/or actuating devices.

Figure 11: Typical Field Bus Communication Physical Model

CONTROLLER

TRANSCEIVER

OPTICAL

ISOLATION

BUS

INTERFACE

TRANSCEIVER

OPTICAL

ISOLATION

BUS

INTERFACE

TRANSCEIVER

OPTICAL

ISOLATION

BUS

INTERFACE

TRANSCEIVER

OPTICAL

ISOLATION

BUS

INTERFACE

TRANSCEIVER

OPTICAL

ISOLATION

BUS

INTERFACE

FIELD BUS

XXXXXX

YYY

SENSOR

DEVICE

CONFIGURATION

MOTOR

STARTER

MOTOR

CONTROLLER