Rockwell Automation 1770,D17706.5.21 SMART TRANSMITTER TOOLKI - Manual (Page 28)

Chapter 3
Using The Smart Transmitter Toolkit
3-9
In this example, the primary variable is read continuously from two HART
field devices that are associated with one 1770–HT1 Communications
Controller. You will notice that the example reads the primary variable
from device 1 and then from device 2. If you want to talk to two HART
field devices at the same time, you must use two 1770-HT1s. Example 3
demonstrates reading the primary variable from two HART field devices
using two 1770-HT1s.
PLCĆ5 Processor
HART
Field
Device
4-20 mA Loop
1770ĆHT1
1770ĆHT16
Smart Transmitter Interface
RIO
HART
Field
Device
4-20 mA Loop
In this example, we used separate data areas for each device. This forced
us to load the device data file number into the JSR input variable prior to
making the call to the STT subroutine.
In the course of operation, if either HART field device does not respond,
we reissue command 0 to try and get a new HART address for the field
device. This example assumes that each device data area is setup with the
standard inputs for command 0, prior to the execution of this logic.
Device 1 uses N10 and F11
Device 2 uses N12 and F13
N14 is the JSR variable
F15 contains both primary variable values
Programming Example 2:
Multiple HART Devices With
Single 1770ĆHT1