FISCHER Mess- und Regeltechnik GmbH
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BA_EN_DE43
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3.3.1 Modbus RTU network
The DE43 is usually connected in a line network structure as a so-called slave
to the Modbus RTU network. Up to 123 bus participants can be operated
without an amplifier on one strand
NOTICE! Star-shaped networks are not allowed.
MASTER
DE43
1
2
DE43
1
2
DE43
1
2
Address 1
Address 2
Address 127
Bus termination
DC
AC
M
Feed
1
2
E
Modbus
5
Fig. 12:
Modbus RTU network
Communication is effected solely via a Modbus master that is also connected to
the bus system. The connected slaves only react to direct commands from the
master, which is why communication between the slaves is not possible.
To guarantee fault-free data transmission, we recommend terminating the end
point of the Modbus RTU network with a 120Ω resistor. These bus terminating
resistors are available as accessories.
It can be connected to an existing Modbus network via a conventional T-piece
(passive TAP).
MASTER
M
TAP
M
Slave
TAP
LT
LT
M
Slave
TAP
DE43
1
2
Supply
1
2
E
DC
AC
Fig. 13:
Modbus connection
