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9.3.3 Bus structure (bus segment)
In a bus structure:
·Connect all devices in line.
·Each device has its own device address.
·You can integrate up to 32 devices (nodes).
Terminate the beginning and the end of your
bus segment with termination resistors (inside
the devices or with 120 Ω/0.25 W termination
resistors).
·Use repeaters (signal amplifiers) to connect bus
segments if there are more than 32 nodes.
·Devices with bus termination switched on must
be powered.
·It is recommended that the master be placed at
the end of a segment. If the master is replaced
with the bus termination switched on, the bus is
out of operation.
·The bus can become unstable if a slave with bus
termination switched on is replaced or is de-
energized.
·Devices that are not involved in the bus
termination can be replaced without the bus
becoming unstable.
Fig. Representation of a bus structure
Slave
Slave Slave Slave Repeater
Slave Slave Slave
Master
T
T
T
T
- Power supply necessary
T
- Bus terminator on
- e.g. UMG 801 Master
- e.g. UMG 96-S2 Slave
9.4 JanBus interface
The JanBus interface:
·Is a proprietary interface which serves to connect
the UMG 801 to modules (e.g. the 800-CT8-A
current measurement module).
·Is located on the underside of the meter and
supplies connected modules with power.
INFORMATION
·The maximum bus length of the JanBus is
100 m.
·Information on connecting modules can be
found in the information products for the
modules.