Spectrum Controls 1756sc-OF8H Series A - Manual (Page 100)

86 ControlLogix ™ Analog HART Modules
Table 7.13 (HART Pass-Through Command Request Reply)
HART pass through command request – reply packet structure
Field Value Definition
Unconnected Message Header
HART Channel Number
0x00 – 0x07 (1 byte) Module input channel
number for HART
command
Status (1 byte)
33 = INITIATE
35 = DEAD (bad request)
Command status
Count (1 byte) Set to 1
Handle (1 byte)
0 (bad when status is 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 back under the following conditions:
• 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.
• Handle is available, meaning no pending handle is still active.
• 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 following conditions are 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.
• The channel is currently updating device information. Theoretically,
pass-through command can be safely accepted after successfully