Rockwell Automation 1794-OF8IH FLEX Isolated Input/Output HART Analog Modules - Manual (Page 18)

Publication 1794-UM065B-EN-E - September 2010
6 About the FLEX I/O HART Analog Module
This value indicates an open wire condition in the loop.
The remote fault and local fault alarms are issued with the same bit whether
the cause is an under or overrange. Monitor the overrange and underrange bits
in your programming software to determine if the problem is a high current or
low current.
Use the HART Capabilities Before using the HART capabilities, be sure that:
• the I/O module and the associated field device are working properly in
the analog 4 to 20 mA mode.
• the I/O module is configured for 4 to 20 mA range.
• the field device is HART capable.
• no more than one HART field device is connected to each channel.
• input filtering is set to a valid (defined) value.
HART Implementation
Overview The FLEX I/O HART modules act as intelligent HART multiplexers.
Basically, the module learns which HART devices are attached to its channels
and then routes HART messages, as appropriate, between the HART field
devices and the flexbus. Since the HART modules act as intelligent HART
multiplexers, HART commands can be issued to the HART modules
themselves.
Communication on the flexbus occurs between the adapter and the HART
module. The adapter converts these messages to the appropriate network
format for communication with the controlling processor. The controlling
processor gets its command from the user program, storing the responses in
its memory.
Chapter Summary In this chapter, you learned about FLEX I/O analog I/O modules and HART
module capabilities. Read the next chapter to learn about configurable features
on your module.
Processor
User program
Adapter FLEX I/O
HART
module HART
Field Device
Command
Response
for example, HART
Command 3)
Flexbus 4…20 mA with
HART signal