Hart Operating Data Records; Hart Command Interface - Siemens SIMATIC ET 200SP HA Manual

HART operating data records

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HART command interface

Data records
The HART commands are sent as so-called external HART requests from the client (e.g. PDM)
to the connected field device using data records. The response of the field device is provided
again in the system using data records.
The 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 I/O 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 completely because the I/O module may
modify the data record after the initial reading with "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 error 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-specific 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 lock of the request data record is reset after the termination or completion of the requested
HART command.
SHC sequence
If a HART command with set SHC bit is sent to the I/O module, this channel is reserved for
HART commands for 2 seconds. That is, no more internal HART commands are sent to the
field device for this channel.
For each additional HART command with SHC bit set, the I/O module reserves this channel
again for HART commands for an additional 2 seconds. Command 3 or 9 for reading the HART
variables starts being sent cyclically to the field device again if a HART command without a
Analog Input Module AI 16xI 2-wire HART HA ( 6DL1134-6TH00-0PH1)
Manual, 11/2017, A5E39408968-AB
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