Rs-422 mode, Rs-485 mode – B&B Electronics ESP902 - Manual User Manual
Page 22
Making Hardware Connections
14
Chapter 2
Manual Documentation Number: ESP901-902_5012m
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
RS-422 Mode
In
RS-422 Mode
the currently selected serial port is configured as an
RS-422 interface supporting four RS-422 signal channels with full
duplex operation for
Receive
,
Transmit
,
RTS
(Request To Send) and
CTS
(Clear To Send). The data lines are differential pairs (A & B) in
which the B line is positive relative to the A line in the idle (mark)
state. Ground provides a common mode reference. To use handshaking,
Flow Control must be set to RTS/CTS during configuration.
N
N
o
o
t
t
e
e
:
:
Refer to Appendix B RS-422 connection pin-outs.
RS-485 Mode
In
RS-485 Mode
the currently selected port is configured as an RS-485
interface supporting transmit (TX) and receive (RX) signal channels
using 2-wire, half-duplex operation. The data lines are differential with
the Data B line positive relative to Data A in the idle (mark) state.
Ground provides a common mode reference.
N
N
o
o
t
t
e
e
:
:
Refer to Appendix C for RS-485 connection pin-outs.
RS-485 Receiver Biasing
RS-485 Receiver Biasing
can be implemented from the
Serial Server
if the network does not supply it. Remove the two side-cover screws of
the
Serial Server
, slide the cover off and re-position the bias jumpers
(shown open in the figure below) to enable biasing (shorting).
Figure 10. Internal Setting to Select RS-485 Bias
N
N
o
o
t
t
e
e
:
:
(For more information on RS-485 Receiver Biasing, see B&B
Electronics RS-422/485 Application Note available at