HART operating data records
A
A.1 HART command interface
Data records
The HART commands are sent as external HART orders to the connected eld device from the
client, e.g. PDM, via data records. The response of the eld device is made available again in the
system via data records.
HART communication may only be handled by one client per channel. If a channel is handled by
several clients, the response made available by the module cannot be allocated to one client
with certainty. The I/O module does not support client management.
Rules
• After having written a request data record, a client must read the response data record before
it may write another request data record.
• The client can evaluate the "processing status" in the response data record: If the "processing
status" indicates "successful" or "error," the response data record contains current response
data or error indications, respectively.
• The response data record must always be read in full as the data record can be changed by
the I/O module after it is rst read with a successful or error status.
If the processing status in the response data record indicates "successful" or "error", the data
record contains current response data or fault displays.
• The client may only write a request data record to the I/O module again when it has read the
response to the previously written request data record via the corresponding response data
record. Otherwise, the response from the I/O module is overwritten.
• The STATUS component in the response frame (HART device status in the response data)
provides information on whether errors have occurred and, if so, which errors.
Each request is stored on a channel-specic basis, and the corresponding request data record is
locked. Another writing of the same request data record is thus not possible and is
acknowledged with BUSY.
The disable of the request data record is reset after the termination or completion of the
requested HART command.
F-AI 8xI 2-/4-wire HART HA
Equipment Manual, 09/2021, A5E50557845-AA 95
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