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

HART operating data records

B.1

HART command interface

Data records
The HART commands are sent over data records to the connected field device as "external
HART jobs" from the client (e.g. PDM). The response of the field device is made available
again in the system via data records.
HART communication may only be used by one client per channel. If a channel is used by
multiple clients, the response provided by the AI-DI 16/DQ16x24VDC HART HA cannot be
reliably assigned to one specific client. The AI-DI 16/DQ16x24VDC HART HA 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 module after it is first read with a successful or error status.
● The client may only write a request data record to the 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 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 disable of the request data record is reset after the termination or completion of the
requested HART command.
SHC sequence
If a HART command with a set SHC bit is sent to the module, this channel is reserved for HART
commands for 2 seconds, i.e. no internal HART command is sent to the field device by the
channel.
The module then reserves the channel for HART commands again for another 2 seconds
following each further HART command with a set SHC bit. Command 3 or 9 for reading the
HART variables starts being sent cyclically to the field device again if a HART command without
Input/output module AI-DI 16/DQ16x24VDC HART HA (6DL1133-6EW00-0PH1)
Manual, 05/2017, A5E39294170-AA
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