User Manual
Compact IO™ Isolated HART Analog Input Module
U ser 's M a n u a l 0 300 21 5- 03 R ev. A
7-36
Table 7-1 5 (HART Pass-Through Request Reply )
HART pass through c ommand request – reply packet structure
Field Value Definition
HART Channel Number 0x00 – 0x03 (1 byte) Module input
channe l number for
HART command
Status (1 byte)
32 = Busy (Queue is already full).
33 = DR_INITIATE
35 = DR_DEAD (bad request)
Command status
Count (1 byte) Set to 1
Handle (1 byte)
0 (bad when st at us is DR_DEAD)
1-255 (good)
The handle for
command complete
query
The command status, the second byte in the reply packet for this module specific
command, can return two different responses, INITIATE, 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:
INITIATE will be sent bac k under the fo llowing conditions:
•
Command and HART Cha nnel number are bot h valid .
•
HART channel is enabled and communication has been estab lished, meani ng at
least the device addressing information is available.
•
Handle is available, meaning no p e ndin g handle is still activ e.
•
HART channel is doing regular data sampling only. No pending device
information gathering is active.
•
No pending pass-through handle is active, meaning handle timeout has not
occurred yet.
•
Device address and delimiter are valid.
•
Received CIP word count is large enough for the entire command packet.
DEAD will be sent back if any of the follow ing conditions are true:
•
Command or HART Chan nel number is invalid.
•
HART channel is not enabled.
•
HART communication has not been establis hed , meaning that the 5-b yte unique
address has not been determined yet.
•
The channel is currently updating device information. Theoretically, pass-
through command can be safely accepted after successfully receiving Command
0, but for simplicity, we 'll track update of the device information as a whole.
•
All other conditioned not generating INITIAT E .
After the pass-through response is sent with a valid handle and a response value
indicating (33) INITIATE, the user can retrieve the data associated with the handle using
the following command message.