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RS485 / RS422
Setting the operating mode on the DIP switch
Operating mode
Two-wire RS485 with termination
Two-wire RS485 without termination
Four-wire RS485 without termination
Four-wire RS485 with termination of receive cable
RS422
Tab. 4-1:
NOTE
RS485 stipulates that the cables should be terminated at both ends of the transmission sec-
tion. The termination prevents signal reflections in the cables and in times of no data trans-
mission, enforces a defined idle state on the bus. This termination can be implemented
using, for example, specific resistors at the screw terminal. It can also be implemented via
the DIP switches on the Mitsubishi Alarm Modem.
RS422 Connection
RS485 2-wire connection (2-wire bus system, half-duplex)
In this operating mode, transmit cables and receive cables are interconnected. If the Mitsubishi
Alarm Modem is installed at the beginning (first station) or end (last station) of the bus system,
the bus system must be terminated by setting the DIP switches accordingly.
Bus Master
4 - 4
Setting the operating mode on the DIP switch
COM2
COM2
DIP 1
DIP 2
1
1
0
0
0
0
1
1
0
0
Fig. 4-7:
The receiving lines are to be connected to
R+ (other end T+) and
Device B
R- (other end T-),
the sending lines to
R+
T+ (other end R+) and
R–
T- (other end R-)
T–
according to the opposite sketch.
T+
Fig. 4-8:
The twisted pair cable is to be connected to
Slave 1
T+ to T+ or R+ and for
T- to T- or R-
R+/T+
according to the opposite sketch.
R–/T–
Slave 2
R+/T+
R–/T–
Slave 3
R+
R–
T+
T–
Interfaces
DIP 3
DIP 4
DIP
1
1
1111
1
1
0011
0
0
0000
0
0
1100
0
0
0000
MITSUBISHI ELECTRIC
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