Rockwell Automation 1794-OF8IH FLEX Isolated Input/Output HART Analog Modules - Manual (Page 127)

115 Publication 1794-UM065B-EN-E - September 2010
Appendix
C
FLEX I/O HART Modules Network Messaging
Overview This appendix discusses:
• How to communicate with theFLEX I/O HART modules via the MSG
or CIO instruction
· The differences between Attributes and Assembly Indexes
· Enhancements to the HART frame
Communication The messaging between the processor and the FLEX I/O HART module is
handled via MSG or CIO instructions, depending on the processor type.
These ladder logic instructions need specific details for proper operation. In
particular, they need four items:
• Class
The Class value for FLEX I/O is 7D hex.
• Instance
The Instance is a number between 1 and 8. This number indicates the
module location relative to the adapter module. Use 1 for the module
connected directly to the adapter.
• Service
The Service value is 0E hex for Get Attribute Single and 10 hex for Set
Attribute Single. Use a Service value of 0E hex to read data from the
adapter and 10 hex to write data to the adapter.
• Attribute
The Attribute value is based on the Attribute Values table.
Handle replaces Preamble. Handle is a number you supply so that the module
returns the Handle with the associated response from the HART command.
The response from the HART command is reformatted to add this handle and
to add additional status information.