Intesis IntesisBox FJ-AC-MBS-1, Руководство пользователя

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IntesisBox
®
ModBus RTU
– Fujitsu
User Manual r1.0 EN
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This information is subject to change without notice
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EIA-485 bus. Termination resistors and Fail-Safe Biasing mechanism
EIA-485
bus requires a 120Ω terminator resistor at each end of the bus to avoid signal reflections.
To prevent fail status detected by the receivers, which are
“listening” the bus,
when all the transmitters
’ outputs are
in three-state (high impedance), it is also required a fail-safe biasing mechanism. This mechanism provides a safe
status (a correct voltage level) in the bus when all the transmitters’ outputs are in three-state. This mechanism must
be supplied by the Modbus Master.
The FJ-AC-MBS-1 device includes an on-
board terminator resistor of 120Ω that can be connected to the EIA-485
bus by using DIP-switch SW4.
Some Modbus RTU EIA-485 M
aster devices can provide also internal 120Ω terminator resistor and/or fail-safe
biasing mechanism (Check the technical documentation of the Master device connected to the EIA-485 network in
each case).