M-Bus - Siemens SENTRON PAC2200 Product Manual

Description
2.5 Communication
2.5.2 RS 485
Permits communication via the MODBUS RTU protocol. This interface features simple
topology and high immunity against EMC interference.
The data is transmitted differentially via two wires A and B. The third wire "COM" serves as
the common ground potential.
Grounding of the cable shield:
The serial Modbus data cable should be shielded. The shield should be connected to
protective ground at one end of the cable at least.
Grounding of the COM line:
Many masters do not have a common terminal. If this is the case, then RS 485 common
should reference the same functional ground as the master (at a single point). If the
master has a common terminal, then the common is connected to it, and it is not connected
to functional ground.
Note
RS 485 termination is recommended!
In order to avoid reflection on the bus cable, we recommend fitting a 120 Ohm terminating
resistor at the beginning and end of the bus cable.
2.5.3

M-BUS

M-BUS is the abbreviation for Meter-Bus according to EN13757. The M-BUS is used as a
fieldbus for the acquisition of consumption data. The data is serially transmitted over a
reverse-polarity protected two-wire line.
PAC2200 data can be read out with an M-BUS master. The PAC2200 is then implemented
as an M-BUS slave.
To read out measurement data stored on the device, the slave address must be known.
The user can give a primary address to the device manually, or use the secondary address
of the device. The secondary address is automatically created from the serial number of the
device and must therefore not be set explicitly. Furthermore, the interface of the PAC2200
must be set to the baud rate used in your M-BUS system. Additionally the user can choose
between two different DIF / VIF codes ("mapping"). In "Mapping 1" the measured values are
coded in more detail with DIF / VIF with the result that all the data records have different
coding.
Different measurement data is available, depending on the connection type, 3P4W or 1P2W.
(With MID devices only connection type 3P4W is possible).
The connection type and the parameter setting in the M-BUS communications menu on the
device display define the data record structure or contents of the RSP_UD2 long datagram.
At the M-BUS interface the setting can be determined by means of the version number in the
header of the RSP_UD2 response datagram of an REQ_UD2 request (see M-BUS
specification)
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PAC2200
Manual, 05/2018, L1V30415167B-02