MBUS-RELA4 - User manual
3.5.2 Slave-Select in secondary addressing
In secondary addressing, the reserved primary address
0xFD
is used to communicate with the slave. A
prerequisite is that the respective M-Bus slave is selected via its secondary address with
Slave-Select
, prior to
any other communication.
Byte no.
Size (bytes)
Value (HEX)
Description
1
1
68
Start character of a long frame
2
1
0B
Length field (L)
3
1
0B
Length field (repetition)
4
1
68
Start character of a long frame (repetition)
5
1
73
Control field (C): SND_UD
6
1
FE
Address field (A): Broadcast address with response
7
1
52
Control information field (CI): Slave select
8-11
4
xx xx xx xx
Secondary address (secondary ID)
12-13
2
96 4D
Manufacturer ID: SLV
14
1
01
Device version
15
1
22
Device type
16
1
xx
Checksum (CS)
17
1
16
Stop character
Table 7: Slave Select in secondary addressing
Response of the selected MBUS-RELA4:
0xE5
The
Manufacturer ID
can be converted to a manufacturer code maintained by the
DLMS User Association
.
An overview can be found here: www.dlms.com/flag-id/flag-id-list
The usage of wildcards (
0xF
) in the nibbles of the bytes 8-15 and thus also the secondary search is
supported by the MBUS-RELA4.
After a
Slave-Select
, the entire communication is performed with the special primary address
0xFD
. Therefore,
Slave-Select
is not discussed again in subsequent examples.
3.5.3 SND_UD (Send user data to slave)
Via
SND_UD
, data are sent from the M-Bus master to the M-Bus slave.
The slave has to acknowledge the correct receipt of the data according to EN 13757 with the single character
0xE5
. An acknowledgement does not necessarily imply processing of the data. Depending on the function,
the slave can also discard the data.
• In the MBUS-RELA4, SND_UD is employed, amongst others, to control the relays.
3.5.4 REQ_UD2 (Read user data class 2 by the slave)
Via
REQ_UD2
, the M-Bus master requests data from the M-Bus slave. The M-Bus slave replies with a
RSP_UD
telegram, containing the requested data.
• In the MBUS-RELA4,
REQ_UD2
is employed to read out the state of the device.
3.6 Communication with the MBUS-RELA4
The supported application cases for the communication with the MBUS-RELA4 are given in the subsequent
examples. The
SND_NKE
is not contained in the examples.
3.6.1 Setting the primary address via SND_UD
This call assigns a new primary address to the MBUS-RELA4. The MBUS-RELA4 is selected with its old
primary address. Adhering to EN 13757, the acknowledgement contains the single character
0xE5
.
Byte no.
Size (bytes)
Value (HEX)
Description
1
1
68
Start character of a long frame
2
1
06
Length field (L)
Continued on next page
Frank Richter, 6 December 2022
© solvimus GmbH
Version: 1.3
Released
Page 17/21
UG_EN_MBUS-RELA4.pdf
