Data Flow Control - Advantech Data Acquisition Modules ADAM 4000 User Manual

E.3 RS-485 Data Flow Control
The RS-485 standard uses a single pair of wires to send and receive
data. This line sharing requires some method to control the direction of
the data flow. RTS (Request To Sent) and CTS (Clear To Sent) are the
most commonly used method.
Intelligent RS-485 Control
ADAM-4510 and ADAM-4520 are both equipped with an I/O circuit
which can automatically sense the direction of the data flow. No
handshaking with the host (like RTS, Request to Send) is necessary to
receive data and forward it in the correct direction. You can use any
software written for half-duplex RS-232 with an ADAM network
without modification. The RS-485 control is completely transparent to
the user.
Figure E-6 RS-485 data flow control with RTS
Appendix E
Appendix E RS-485 Network E-7