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14 Chapter 2 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
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.
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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.
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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
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o
o
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e
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(For more information on RS-485 Receiver Biasing, see B&B
Electronics RS-422/485 Application Note available at www.bb-
elec.com)