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RS-422 Connections
76 Appendix B Manual Documentation Number: ESP901-902_0508m
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 – www.bb-elec.com
B&B Electronics Ltd – Westlink Commercial Pk – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445 – www.bb-europe.com
Figure 67. RS-422 Connections with Flow Control
In the RS-422 mode, TXD lines are outputs and RXD lines are inputs.
Connect the
Serial Server TXDB(+) line to the RXDB(+) line of the
serial device, and the Serial Server TXDA(-) to the RXDA(-) of the
serial device.
If Flow Control is set for RTS/CTS, connect the
Serial Server
RTSB(+) to CTSB(+) of the serial device and the Serial Server
RTSA(-) line to the CTSA(-) of the serial device. Connect from the
Serial Server CTSB(+) line to the RTSB(+) of the serial device and
from the Serial Server CTSA(-) line to the RTSB(+) line of the serial
device.
If connecting to Receive Only RS-422 devices, connect from the
Serial Server TXDB(+) and TXDA(-) lines to the receive pairs on all
serial devices.
Ground is signal ground and provides a common mode reference for
the RS-422 Receiver and Transmitters.
N
N
o
o
t
t
e
e
:
:
The RS-422 mode can be used for full duplex 4-wire RS-485 operation
provided that the serial server is acting as a sole master connecting to
all the slave devices, and all slave devices share the Receive signal
lines to the master. Set Flow Control for none, and omit connections to
RTS/CTS line pairs.
Serial Server pin-out
in RS-422 mode
RS-422
Device
RS-422 Signal Names DB-9
Pin#
Connections Signal
Receive A (-) RXDA(-) 1 TDA(-)
Receive B (+) RXDB(+) 2 TDB(+)
Transmit B (+) TXDB(+) 3 RDB(+)
Transmit A (-) TXDA(-) 4 RDA(-)
Ground GND 5 GND
Clear to Send A (-) CTSA(-) 6 RTSA(-)
Clear to Send B (+) CTSB(+) 7 RTSB(+)
Ready to Send B (+) RTSB(+) 8 CTSB(+)
Ready to Send A (-) RTSA(-) 9 CTSA(-)