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Rockwell Automation 1770,D17706.5.21 SMART TRANSMITTER TOOLKI User Manual

Page 11

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Chapter 1

Introducing The Smart Transmitter Toolkit

1-4

To help explain what the STT subroutine can do for you, let’s examine how
communication occurs between a PLC processor and a HART field device.

The PLC-5 processor sends a Smart Transmitter Interface packet to
the 1770-HT1 as block-transfer write (BTW) data.

The 1770-HT1 forwards the Smart Transmitter Interface packet as a
HART packet to the HART field device.

The HART field device receives the HART packet and then responds
back to the 1770-HT1 with a HART packet that contains the
appropriate HART digital data.

The 1770-HT1 routes the response back to the PLC-5 processor in a
Smart Transmitter Interface packet as block-transfer read (BTR) data.

90065

HART Response

HART

Field

Device

BTW Data

RIO

BTR Data

HART Poll

4Ć20 mA Loop

1770ĆHT1

Smart Transmitter

Interface packet

HART

packet

1770ĆHT16

Smart Transmitter Interface

PLCĆ5 Processor

How a PLCĆ5 Processor

Communicates With a HART

Field Device