User`s manual

4-6 Smartio C168H/PCI User’s Manual
RS-485 Programming for Opt8J
If you intend to use Opt8J for RS-485 communications, follow the RS-485
programming guide given below, and refer to the chapter Connection Option (Opt8x)
and Cable Wiring for more Opt8J RS-485 operation details.
The Opt8J option only supports 2-wire half-duplex RS-485 communications. Data
+/ − pins are used for both data transmitting and receiving, depending on the RTS
signal.
The port switch for each port should be set to the On position. The port is used for
transmitting data if RTS is asserted and is used for receiving data if RTS is not
asserted.
This RTS scheme is suitable for any system that permits RTS control from within
application programs. This includes Windows NT, Windows 95/98, DOS, and UNIX.
How to transmit and receive data under Windows NT and
Windows 95/98
We recommend that you configure Smartio C168H/PCI ports as follows to acquire
precise timing control when using RS-485 2-wire transmission.
There are 2 ways to control RS-485 2-wire transmission.
Solution 1
The following model is commonly used for RS-485 2-wire transmission.