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Acyclic data exchange: Reading measurement data from M-Bus devices
The measured values are transferred from the PN/M-Bus LINK to the S7 control system
through data records. The PN/M-Bus LINK always reads all available measured values from
an M-Bus device and saves the measured values as a data record.
A data record is read via "Read Data Record" (RDREC). The default index number is 600.
A data record contains the user data from the RSP_UD response telegram with the
transmitted measured values, starting with the first DIF. The telegram header is not included
in the data record.
The data block with the measured data contained in the data record is transferred to the
S7 controller without any changes. The corresponding evaluation and further processing of
the measurement data must be performed by the user program.
A data record has the following structure:
Byte
0 ... 1
2 ... 3
4 ... 5
6 ... <END>
1) CI field (control information field) from received RSP_UD response telegram
PN/M-Bus LINK
Operating Instructions, 03/2018, A5E44260928-AA
Name
Data type
ResponseCode
UINT16
Mode
UINT16
Length
UINT16
Measured data
M-Bus STRUCT
4.1 Cyclic and acyclic data exchange
Value
Description
Device error information
0
No error
1
No data available
2
M-Bus communication error - no data
available
Specification of the M-Bus data
structure
0
Variable data structure
CI
= 72h/76h
1
1
Fixed data structure
CI
= 73h/77h
1
Total length of the M-Bus STRUCT in
bytes
Measured data from M-Bus device,
starting with the first DIF (EN1434-3)
Functions
17
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