M-BUS-EK Datasheet, PDF (8/20 Pages) Silicon Laboratories – AC to DC power adapter

Wireless M-Bus-EK
The power consumption of the meter depends on the parameter settings. The PC application allows the following
parameters to be set:
 Transmit Period
 Data Field Length
 M-Bus Mode
 Transceiver Mode
 Data Select
 Pulse Frequency
 Encryption
 LCD Enabled
8.1. Transmit Period
The transmit period can be set for 1 second to 3600 seconds (5 minutes). The C8051F930 MCU will sleep for this
period with the Si4431 EZRadioPRO in shut-down. Then, it will wake up, take a measurement, and send the data.
The Transmit period has a large effect on the power consumption. A long transmit period is necessary to achieve
multi-year battery life.
8.2. Data Field Length
The data field length sets the length of the application payload in the M-Bus packet. The minimum length is 2,
including the required CI byte. The maximum is 100 bytes. If AES encryption is enabled, this field must be a
multiple of 16.
8.3. M-Bus Mode
The following menus can be used to select the M-Bus mode:
 Mode S: 32,768 cps Manchester encoding
 Mode SL: same as above with a very long preamble
 Mode T: 100 kcps, three-out-of-six encoding
 Mode R: 4800 cps, Manchester encoding
Mode T provides the highest data rate and gives the lowest power consumption. The current consumption of Mode
SL with the long preamble is slightly higher than Mode S. The long preamble is not necessary for the Si4431
EZRadioPRO. Power consumption is the highest using Mode R. Sending a long packet using Mode R may take
hundreds of milliseconds. Mode T2, Mode S2, and Mode R2 may be selected by choosing TX and RX in the
Transceiver mode menu. According to the specification, Mode R should always use TX and RX. For additional
information about M-Bus modes, refer to “AN451: Wireless M-Bus Software Implementation” and EN 13757-4.
8.4. Transceiver Mode
The Wireless M-Bus demo PC application provides two transceiver modes:
 TX
 TX and RX
If the TX only mode is selected, the meter will sleep for the transmit period, wake up, and transmit its data. If the TX
and RX mode is selected, the meter will wake up and send an access demand message. If the access demand
message is acknowledged, the meter will send its data to the other device.
When a meter reader (Other) device is present, the current consumption of the two-way communication is highest.
Because there is overhead associated with the two-way data transfer. If the meter reader (Other) is not present, the
two-way meter only needs to send the access demand message and wait for the response time. Still, the response
time is long compared to the message length; so, the one-way communication usually provides the lowest power
consumption.
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