Interfaces of the Device
106358_en_02
PHOENIX CONTACT
53
4.2.1.2
Termination
Always turn on the termination in a 4-wire point-to-point connection (RS-422 / RS-485). A
sender termination for the quiescent level of the receiver must exist on the remote station.
Turn on the termination only at the two ends of the lines in a 2- or 4-wire multi-point connec-
tion (RS-422 / RS-485).
Figure 4-6
Termination possibilities RS-422 / RS-485 (intern)
4.2.1.3
Transmitter Control
Switching between half-duplex and full-duplex is carried out by the DTR signal.
Full-duplex (DTR inactive / off):
The transmitter is always active and is not turned off on intermissions.
The receiver is always active.
Half-duplex (DTR active / on):
The transmitter is activated during the transmission. On intermissions, the transmitter is
highly resistive.
The receiver is disabled during the transmission. The operating device does not receive the
own transmit data at the receiver.
Table 4-4
Resistance values termination RS-422 / RS-485
Designation
Value
R1
120 Ohm
The switch positions for ON or OFF are printed onto the operating device. Only the spec-
ified switch positions are allowed.
Table 4-5
Termination switch RS-422 / RS-485
Switch position
Function
ON
Receiver termination (120 Ohm)
OFF
No receiver termination
