Allen-Bradley 1794-IE8H, User Manual, Page: 93 / 146

1 Publication 1794-UM063A-EN-P - March 2006
Appendix
B
FLEX I/O HART Module Commands
What This Appendix
Contains
Read this appendix to learn the module commands to and from FLEX I/O
HART modules.
Protocol Overview
HART field communications protocol is widely accepted in the industry as the
standard for digitally enhanced 4 to 20 mA communication with smart field
instruments. The HART protocol message structure, command set, and status
are discussed in this appendix.
The HART command set is organized into three groups and provides
read/write access to a wide array of information available in smart field
instruments:
•
Universal commands provide access to information that is useful in
normal plant operation such as the instrument manufacturer, model,
tag, serial number, descriptor, range limits, and process variables. All
HART devices must implement universal commands.
•
Common practice commands provide access to functions, which can be
carried out by many devices though, not all.
•
Device-specific commands provide access to functions that may be
unique to a particular device.