iSMA-B-MG-IP User Manual
www.ismacontrolli.com
DMP260en | 1st Issue rev. 6 | 05/2022
page 19 of 29
6 M-Bus Gateway
Figure 10. The iSMA-B-MG-IP M-Bus gateway
The iSMA-B-MG-IP serves as an M-Bus gateway using either one of two protocols: TCP IP
or UDP IP.
6.1 M-Bus TCP IP Gateway
The device simultaneously supports up to
4 M-Bus TCP clients
. If the fifth device is to be
connected to the meter gateway, TCP connection will be rejected. In order to secure the
meter gateway before filling up the call list, a mechanism for monitoring each M-Bus TCP
IP connection was introduced. Every 45 seconds a query is sent to the devices connected
to the bus. If a device does not response to the query, after 2 seconds another query is
sent. If the device does not respond three times, the meter gateway closes the
connection.
The iSMA-B-MG-IP device has a built-in M-Bus TCP IP to M-Bus interface gateway, which
allows to connect additional 3
rd
party M-Bus devices using the bus. In order to ensure
proper operation of the M-Bus gateway, please make sure that the baud rate of the M-
Bus interface of all the devices connected to the bus (gateway and an addition devices)
are the same.
Operation of the gateway is based on sending the M-Bus TCP IP query by the M-Bus. Data
frame from query is converted to M-Bus and sent to the bus. Then the iSMA-B-MG-IP
device waits for an answer from a device connected to the bus; if the meter does not
respond within the estimated time defined by the M-Bus Timeout parameter (by default,
2000 ms), an exception is returned: error code 0x0B. If the slave answers the correct
frame, it is converted to M-Bus TCP IP and sent to the master.
6.2 M-Bus UDP IP Gateway
The device simultaneously supports up to 2 M-Bus UDP clients. In order not to miss the
second
client’s
packet delivery at high intensity periods of incoming data, the data from
the first client is read from the lwIP in the loop, and only two frames are buffered with
different addresses. The response via the UDP protocol is sent to the same port it came
from (the default port for UDP protocol is 10002).
