User manual

1 Publication 1794-UM063A-EN-P - March 2006

Appendix

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.