Rockwell Automation 1770-HT8 SMART TRANSMITTER User Manual

Page 10

Preface

P-3

The Smart Transmitter Interface Products create a communication interface
between programmable controllers and HART field devices. They are
compatible with HART field devices and with hand-held terminals capable
of supporting the physical and data link layers of the HART protocol.

This manual uses the following terms as defined below.

Actuator: any one of several field devices that provide control functions
using a 4-20mA input control signal. Actuators that support the HART
protocol are designated as being “smart”.

BTR: Block Transfer Read

BTW: Block Transfer Write

Clear: (a bit) equal to 0

Hand-held terminal: a smart terminal product capable of functioning as
either a primary or secondary master to one single HART device, using the
HART protocol; this terminal allows the operator to monitor and configure
the HART field device (e.g. Rosemount 268)

HART: Highway Addressable Remote Transducer

HART field device: a transducer or actuator that supports the HART
protocol

- 4-wire: refers to a HART field device drawing power from an

external power source

- 2-wire: refers to a HART field device drawing power from the 4-20

mA loop

HART protocol: a protocol that provides digital communication over an
industry-standard 4-20 mA process control loop at the same time as the
value of a process control variable is being transmitted as a 4-20 mA signal

Host Processor: the programmable controller or host computer (generally
a PC) connected to the Communications Controller over the RIO, or the
host computer connected to the Communications Controller’s RS-232 port

mA: milliamp; one-thousandth of an Ampere

Multidrop: multiple HART field devices (to a maximum of 15), connected
in parallel, per channel on a terminal block

PLC: Programmable Logic Controller; an Allen-Bradley programmable
controller