МBU-250 starts to operate immediately after connecting
the supply voltage to it. The algorithm of work is as follows:
Starting initialization mode (0.2-0.3 s)
For about 0.2-0.3 s the device is busy with initialization
of important parameters. During initialization the output
is forbidden and the output voltage is 0 V. Leds ‘on’ and
‘prot’ (protection) are active. the output becomes active,
the unit then measures current consumption of the connected
slaves. Led ‘prot’ is turned off, led ‘out’ (allowed output)
and ‘com’ (transmit) become active. If short circuit, the
output is held forbidden and after a few second a new check
is done, while led ‘prot’ becomes active, leds ‘out’ and
‘com’ are turned off.
Normal operation mode
Continuously the unit measures current consumption of the
connected slaves. If the consumed current becomes higher
than 385 mA, the led 'ovr' is turned on. If the consumed
current becomes higher than 410 ± 5mA, the output is forbidden
and turned off. When connecting the device to a collecting
unit (personal computer, etc.) through one of input interface, the
collecting unit can transmit data to any slave device in
the m-bus network. In this case the MBU-250 is a dedicated
bridge for the connection between computer and slave devices.
The data is transmitted immediately, without delay. When
a slave device is sending information, this data is first
decoded and then send via input interfaces, with no delay.
This is indicated by the blinking of led ‘com’. It is possible simultaneously to
transmit/receive data. If collision (two or more slave devices
send instantly), the led ‘col’ (collision) is turned on,
although the data is transmitted to selected interface (RS-232, RS-485, USB or m-bus slave).
MBU-250 can also serve as a repeater in larger networks, where expand to more than 250 devices is
needed. It has m-bus slave input, which is 1.2mA load for the external master. If used, everything
on m-bus input goes to m-bus output and vice-versa.
