Rockwell Automation 1794-OE8H FLEX I/O HART Analog Modules User Manual - Manual (Page 115)

1 Publication 1794-UM063A-EN-P - March 2006
Appendix
D
FLEX I/O HART Modules Network Messaging
What This Appendix
Contains This appendix discusses:
• How to communicate with the FLEX 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 HART I/O 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 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.