Industrial
Electronic Devices
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User Manual
M-Bus / M-Bus Wireless / MQTT
Document code: MN67931_ENG Revision 1.200 Page 13 of 49
ETHERNET:
The Ethernet connection must be made using Connector3 of HD67931-B2 with at least a Category 5E cable. The maximum length of the
cable should not exceed 100m. The cable has to conform to the T568 norms relative to connections in cat.5 up to 100 Mbps. To connect the
device to an Hub/Switch is recommended the use of a straight cable, to connect the device to a PC/PLC/other is recommended the use of a
cross cable.
M-BUS:
The M-Bus is a unpolarized bus.
A two wire standard telephone cable (JYStY N*2*0.8 mm) is used as the transmission medium for the M-Bus. The maximum distance
between a slave and the repeater is 350m; this length corresponds to a cable resistance of up 29Ω. This distance applies for the standard
configuration having Baud rates between 300 and 9600 Baud, and a maximum of 250 slaves. The maximum distance can be increased by
limiting the Baud rate and using fewer slaves, but the bus voltage in the space state must at no point in a segment fall below 12V, because
of the remote powering of the slaves. In the standard configuration the total cable length should not exceed 1000m, in order to meet the
requirement of a maximum cable capacitance of 180nF.
(Taken from M-Bus specifics)
