Owner manual

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.
➊ The PLC-5 processor sends a Smart Transmitter Interface packet to
the 1770-HT1 as block-transfer write (BTW) data.
➋ The 1770-HT1 forwards the Smart Transmitter Interface packet as a
HART packet to the HART field device.
❸ 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.
➍ 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
420 mA Loop
1770HT1
Smart T ransmitter
Interface packet
➊
❸
➋
➍
HART
packet
1770HT16
Smart Transmitter Interface
PLC5 Processor
How a PLC5 Processor
Communicates With a HART
Field Device