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SIMATIC S7 HART Analog Modules
4.8.3 HART Communication Data Records
Transfer data
records
Coordination
rules for HART
communication
4-30
HART communication can be operated by up to 7 clients, using two separate
channels each. There are 14 separate data transfer areas for this purpose, 7
for channel 0 and 7 for channel 1. Each transfer area consists of a command
data record and a response data record.
Each client / channel is allocated fixed data record numbers:
Channel Client / Data
record
1 2 3 4 5 6 7
0 Command 10 14 18 22 26 30 34
0 Response 12 16 20 24 28 32 36
1 Command 50 54 58 62 66 70 74
1 Response 52 56 60 64 68 72 76
Each client may only use the data record numbers allocated to its transfer
area.
For example, for client 6, channel 0: the command is data record 30 and
the response is data record 32.
After a client has written a command data record, it must read the
response data record before it can write another command data record.
The transfer area of each client is allocated a data ready bit which is set
when new data can be fetched (see Figure 4-20).
In Master Class 2 the client can evaluate the “processing state” in the
response data record: if the “processing state” indicates “successful” or
“error,” the data record contains current response data or error bits
respectively.
The data record must always be read completely, as the the data record of
the module can be changed after the first reading.
The status section of the data record provides information on any errors
that have occurred.
The HART burst mode cannot be used by more than one client at any one
time (that is, only one client can set this operating mode with a
command).
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04