1-250 intended for measuring instruments
0, 251-255 special addresses
8-digit serial number (along with manufacturer ID, version, and type of device)
3-digit ID, in MX devices = BER
In order for the M-Bus units to be addressable, they must be given an ID – an “M-Bus address.” This address is divided into a primary and a secondary address.
The Primary Address is intended for fast device access. It consists of a number from 1 to 250. This number can be allocated to any M-Bus subscriber. The meter can then be addressed and read using this number.
If two or more units have been allocated the same primary address, a collision will occur during direct reading as several units try to answer the master simultaneously.
Primary Addressing: 1 - 250 intended for measuring instruments 0, 251-255 special addresses
Secondary Addressing: 8-digit serial number (along with manufacturer ID, version, and type of device)
Manufacturer ID: 3-digit ID, in MX devices = BER
The secondary address was created for such a case. It is device-specific and normally corresponds to the serial number of the unit. In its entirety, the secondary address consists of the serial number, the manufacturer ID, version, and type of device. By setting the primary (253) and secondary address, each device can be specifically addressed. As the secondary address consists of 8-digit positions, the probability of a coincidental match is very small.
In addition to the identification described above, each device has a manufacturer ID. In MX, this is BER. Other manufacturer designations are, e.g., REL = relay.
SPECIAL PRIMARY ADDRESS
The primary addresses 0 and 251 to 255 are reserved for special tasks, and should not and cannot be used for device addressing. The address 0 is used for the device initial state; i.e., the device has not yet been addressed and put into operation using this number. The M-Bus modules are also supplied with the primary address of 0, unless the customer has requested otherwise.
- 251, 252 possible later use in the standard
- 253 for secondary addressing
- 254 for commands to all devices with a reply
- 255 for commands to all devices without a reply
The M-Bus is based on European standard EN 1434 as a normed interface for calorimeters and is used for the teletransmission of meter data. The normed data protocol is dealt with in Part 3 of EN 1434. Apart from calorimeters, water, gas, and, electricity meters can sometimes be equipped with M-Bus. M-Bus has been standardized since 1997. Meters that were supplied with M-Bus interfaces before this date do not fully correspond with the standard.
START-UP OPERATION SEQUENCE FOR M-BUS MODULE
Start-up operation of the M-Bus modules and other bus subscribers must proceed as follows:
- Setting the reference day If the terminal units are to be programmed with a reference day, the desired reference day must be set in the measuring instrument using the chip card before connection to the M-Bus modules
- Read-out and addressing In order to be able to read out the serial number and the current measurement data from the connected measuring instrument, a command must be sent to all M-Bus modules: Send the command “Read-out” (send UD 51d0) to all modules => Read out the serial number of the device and => set the secondary address
- Search for primary and secondary addresses After that, the search for modules can be started. Initially, all primary addresses are queried and tagged as free, programmed, or multiple allocations. After that, the secondary addresses are searched and listed.
- Addressing the device (allocation of primary address) In the following steps, these modules can now be allocated with a freely programmable address.
- Reading the initial value Finally, the current memory content of the measuring instruments is read from each module.
- Write a project list After completion, a list should be compiled in which the primary address, the corresponding serial number (secondary address), type of device, the initial value, and the installation location is apparent.
See our Glossary for additional assistance.