Data Format; M-Bus Specification; M-Bus Protocol - Camille Bauer EMMOD206 Mode D'emploi

8.2.2 Data format

All transferred measurements are primary values. Instantaneous values are represented as 16-bit integer numbers and energy
meters as 32-bit integer numbers. The corresponding units and decimal point positions are changing in accordance with the
transformer ratios of the basic unit and will be delivered in the data telegram in conformance with the standard.
The measurements for frequency F [Hz] and power factor PF [ ] are not described in the standard. Therefore these data is
transferred as ASCII string, as suggested by the standard.
The largest available energy unit for M-Bus is MWh. But depending on the settings of the transformer ratios, larger unit up to
GWh may occur. In such a case the error flag in DIF is set and the user has to take care himself for a correct interpretation.
8.2.3 Data points and assignments
The transfer sequence of the measurements always corresponds to the table lines, voltages first and power mean-values last.
Measurements which are invalid for the selected system will not be transferred.
On master side normally the „data points" will be assigned in the received sequence. Therefore it's recommended to perform
all settings of the basic unit first before arranging the data analysis in the master.
For a better distinction of measurements with the same unit, the additionally sent information in the rows Module, Memory
and Tariff can be used.
Only the instantaneous values marked with a „•" are available in the corresponding system.
9. M-Bus specifi cation
Detailed information about M-Bus is available via the webpage http://www.m-bus.com and the standard EN1434-3.
Wiring for M-Bus is performed via a pair of wires of a standard phone cable (e.g. JY(St)Y 2 x 2 x 0.8 mm). The polarity does
not matter. However, it should be noted that level converters used for PC connection often are not galvanically isolated, but
the bus works with voltages up to 40 V.
For a standard configuration, with baud rates between 300 and 9600 baud and a maximum of 250 slaves, the maximum di-
stance between master and slave is 350 m (approx. 1150 ft). The maximum distance increases if a lower baud rate is selected
or if the number of slaves is decreased.

10. M-Bus protocol

10.1 Addressing
The EMMOD206 supports both primary and secondary addressing.
For the primary addressing you have to assign via the keys a unique address in the range 1...250 to each device connected
to the bus. The requests from the master will then contain this address and the slave responds if there is a match.
For the secondary addressing the master uses the primary address 253 (Broadcast, Selection) and in addition transmits the
desired identification consisting of 8 bytes (4 serial number + 2 manufacturer + 1 generation + 1 medium). Because the serial
number of the EMMOD206 is guaranteed to be unique, no double addressing can occur and no address setting on the device
is necessary. All subsequent requests with primary address 253 will then be answered by the selected device until a new
selection is detected. Using the wildcards F resp. FF ID elements will be masked, by which the master is able to perform an
efficient search for new devices.
10.2 Supported dialogs
10.2.1 Reset SND_NKE / ACK
➤ Request from master
SND_NKE
10 40 FF 3F 16
By using the broadcast address (FF=255) the master causes all slaves to perform a communication reset with acknow-
ledge by ACK.
➤ Answer of the slave
ACK
E5
10.2.2 Data request using primary addressing REQ_UD2 / RSP_UD
➤ Request from master
REQ_UD2
10 7B 03 7E 16
The master requests data from slave no. 3.
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