User Manual

Compact IO™ Isolated HART Analog Output Module
User’s Manual 03 00217-03 Rev. A
7-30
HART Get Device Information - reply packet structure
Field Value Definition
HARTSlot2Units (1 byte) CMD#33, Byte 13, 0 if not present
Output module use only.
HARTSlot3Units (1 byte) CMD#33, Byte 19, 0 if not present
Output module use only.
HARTPVLowerRange (4 bytes – Floating Point
Value)
CMD#15, Bytes 3-6
HARTPVUpperRange (4 bytes – Floating Point
Value)
CMD#15, Bytes 7-10
Pad for 32 bit alignment (3 bytes)
The command status, the second byte in the reply packet for the module specific
command, can return three different responses, SUCCESS, RUNNING and DEAD.
These responses echo the state of the module at the time the command is sent. The
conditions for each response are as follows:
SUCCESS will be sent back when all of the following conditions are met:
 Command and HART Channel number are both valid.
 HART channel device information is available.
RUNNING will be sent back when all of the following conditions are met:
 Command and HART Channel number are both valid.
 HART channel is enabled and communication has been established, meaning at
least the device addressing information is available.
 HART channel is already in the state of gatherin g devi ce i n fo rmation. Reply
will be sent back without additional events triggered.
DEAD will be sent back if any of the following conditions is true:
 Command or HART Channel number is invalid
 HART channel is not enabled
 HART communication has not been established, meaning that the 5-byte unique
address has not been determined yet.
 All other conditioned not generating RUNNING or SUCCESS.
7.4.2 HART Pass-Through Command
The HART Pass-Through Command can be used to send any HART command including
universal, common practice or device specific, directly to a field device. The module in
this case could be considered a HART bridge. There can be two (2) instances of a HART
pass-through message being serviced, meaning the pass-through message queue is 2
deep. The HART pass-through response will be qu eued the moment the command is
received, if the queue spaces are not already in use, and be dispatched after at least a full
scan is done. In other words, after servicing a pass-through, the HART module will make
sure all enabled HART channels have updated variable values before another pass-
through is placed into service.
All HART pass-through commands require a series of messages to be exchanged. First, a
pass-through command request must be sent to the HART module to initiate the pass-
through command. The HART module will respond to the command request with a
command request rep ly that includes a handle that can be used to obtain the pass-through
message response. Once the handle is received, the user may issue a Get Command
Query to obtain the status of the pass-through command and the pass-through command
response data, if it is available.
There is a handle timeout associated with the final reply message. After the HART
module obtains the requested information from the HART device, it will start a handle