Rockwell Automation 1794-OF8IH FLEX Isolated Input/Output HART Analog Modules - Manual (Page 100)

Publication 1794-UM065B-EN-E - September 2010
88 Configure Module Messaging
HART Pass through Message Overview
FLEX I/O modules have a HART Pass through messaging mechanism that
provides the user the ability to send any HART command to the HART device
using MSG instructions.
There are 5 module commands related to Pass through:
• Pass through Init
• Get Pass through message Query Status
• Read Pass through Reply
• Select Handle
• Flush Queues(rarely needed).
Pass through Init is used to instruct the module to initiate a HART Pass
through operation by sending the needed information for a HART
Pass through request to the module. The "Get Pass through message status"
read command will return status of a Pass through operation that will let you
know if the pass through HART message reply has been received by the
module from the device. Once the "Query Status" shows that the reply is ready
then you can issue a "Read Pass through Reply buffer" operation to retrieve
the reply from the module.
Each channel has a separate buffer to hold a pass through request so you can
have 8 requests running at once. The module discards a reply being held in a
buffer if the reply has not been retrieved from the module within 50 seconds.
There are two types of HART Pass through Init requests, one is called
"EASY-HART" and the other is called "FULL-HART". The EASY-HART
method is simpler, requires less data, and does not require you to know the
details of creating a fully formatted HART message as defined by the HART
Object Attribute 0xA7
Reply Size 0
Request Size 2 bytes
Reset Device Information – Request Packet Structure
Offset Field Value Definition
0 Select Channel 0…7 Channel to reset
1 Pad NA
Total = 2 bytes
Reset Device Information – Packet Structure
Field Value Definition