TECHNICAL DESCRIPTION Wired M-Bus • Water Meters flowIQ® 2101
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Kamstrup A/S · Technical Description · 55121944_A1_GB_08.2016
5.5
M-Bus master to M-Bus water meter
Communication on the M-Bus is initiated by the M-Bus Master. After this the addressed M-Bus water meter
replies. Basically, there are 2 different communication sequences (from M-Bus Master to M-Bus water meter):
SEND -> CONFIRM
REQUEST -> RESPONSE
When using ‘SEND -> CONFIRM’ the M-Bus Master sends a command or data to the M-Bus water meter, that
replies with an acknowledgement (ACK). The acknowledgement (ACK) just means that the M-Bus water meter has
received the telegram successfully, but it has not necessarily accepted the contents.
When using ‘REQUEST -> RESPONSE’ the M-Bus Master sends a request to the M-Bus water meter, which in return
replies with a datagram according to the request.
The M-Bus water meter only supports ‘Mode 1’ data format where all multi-byte data values to and from the M-
Bus water meter are transmitted with Least Significant Byte (LSB) first.
In the default application the FCB / FCV bit in the C-field is not used and the M-Bus water meter accepts both FCB =
0 and FCB = 1.
The M-Bus water meter does not use DFC (Data Flow Control) / ACD (Access Demand) bits, which means that both
bits will always have the value 0 in the C-Field from the M-Bus water meter.
The following describes the individual M-Bus telegrams, from M-Bus Master to M-Bus water meter and from M-Bus
water meter to M-Bus Master, that are supported.
REQ_UD1:
Short frame. Request for time-critical data alarm.
Start character
10h
C-field
5Ah or 7A
A-field
xxh or FDh
Checksum
Xxh
Stop character
16h
REQ_UD2:
Short frame. Request for data from the M-Bus interface.
Start character
10h
C-field
5Bh or 7B
A-field
xxh or FDh
Checksum
xxh
Stop character
16h
REQ_SKE:
Short frame. Status request.
Start character
10h
C-field
49h
A-field
xxh or FDh
Checksum
xxh
Stop character
16h
