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RS485 4-wire connection (4-wire bus system, full-duplex)
The terminals of the 2 twisted-pair cables are wired in the same way as for the RS422 connec
-
tion. Both twisted-pair cables must be terminated if the Mitsubishi Alarm Modem is installed at
the start or end of the bus cables. The termination of the receive cables is activated via the DIP
switches. The transmit cables must be terminated externally (see figure arrow).
E
ATTENTION:
Always ensure that the end devices are terminated correctly.
Incorrect or missing termination may give rise to communication faults.
4.5 Mitsubishi FX at RS485/422
The Mitsubishi FX is to be connected via the optional RS485-BD or RS422-BD to the optional
COM2 of the Mitsubishi Alarm Modem, using 5-wire twistedpair cable. The Alarm Modems DIP
switches 3 and 4 must be set to OFF therefore. Perhaps the termination is to be set via DIP
switches 3and 4.Moreinformation onthese DIPswitches areto befound inchapter 4.4ofthis
manual.
The wiring shall become clear by this depiction:
Interfaces Mitsubishi FX at RS485/422
Mitsubishi Alarm Modem 4-5
COM2
Slave 1
T–
T–
T+
T+
(0V
)
R–
R–
R+
R+
Slave 2
T–
T+
R–
R+
Slave 3
T–
T+
R–
R+
Fig. 4-9:
The twisted pair cables are to be con
-
nected according to the opposite sketch.
For termination of the sending line, put a
resistor (120 Ohm/0,5 W) between the
T+ and T- terminals.
Resistor
COM2
Mitsubishi FX
T–
SDB
T+
SDA
(0V
)
R–
RDB
R+
RDA
SG
422-BD/485-BD
Fig. 4-10:
Connection of the modem at the
Mitsubishi FX via the optional
RS485/422-BD