L-INX User Manual
211
LOYTEC
Version 4.0
LOYTEC electronics GmbH
10 M-Bus
10.1 Introduction
The M-Bus (Meter-Bus) is a European standard (EN 13757-2, EN 13757-3) designed for
remote reading of meters. With its standardization as a galvanic interface for remote readout
of heat, water, and energy meters, this bus has become an important interface for automatic
meter reading applications with different vendor‘s meters on the same cable.
The M-Bus is a serial bus, which is controlled by a single bus master. This master can
request data from several slave devices connected to the network. The data transmission
from master to slave is done by a modulation of the output voltage (36 V means a logical
‗1‘, 24 V means logical ‗0‘). During data transmission from slave to master the current is
modulated (1.5 mA represent the logical ‗1‘, 11-20 mA represent a logical ‗0‘). M-bus
devices can be powered over the bus. The number of devices which can be powered
depends on the M-Bus transceiver used.
10.2 Hardware Installation
For using the M-Bus with the device an external M-bus interface with an RS-232 connector
is required. The external interface must be connected to the LOYTEC device either via the
serial connector or the extension port EXT. The M-Bus functionality must be enabled on the
device itself.
10.2.1 Console Connector
When using the serial console connector, the M-Bus interface is enabled on the device by
setting DIP-switch 7 to ON. This disables the console of the device and activates M-Bus
over the console connector. After the device is rebooted, the M-Bus is active on the device.
When rebooting the device with M-Bus activated and the console connected, a couple of
boot messages are displayed in the console, before the console is turned off.
If the console is needed again, set the DIP switch 7 to OFF and reboot the device. This is
required, if the firmware shall be updated over the serial port using the LSU tool.
When using the L-MBUS coupler, connect the L-MBUS to the device‘s console connector
via a Null modem cable (female to female sub-D connector) as shown in Figure 164. On the
L-MBUS remove the jumper as indicated on the front label.
