Moxa Technologies RS-485 Programming, Automatic Data Direction Control Mode Recommended

RS-485 Programming

If you intend to do RS-485 communication with Industio CI-134 Series, please follow the RS-485 programming guide below and also refer to the chapter, “Connection Cable and Cable Wir ing”, for more RS-485 operation details.

The Industio CI-134 Series supports only 2-wir e half-duplex RS-485 communication. Data+/- pins are served for both data transmitting and receiving,

depending on the mode selected: either Automatic Data Direction Control or By RTS mode.

Automatic Data Direction Control Mode (Recommended)

Automatic Data Dir ection Contr ol scheme is the best solutions for RS-485 applications. The mode switch for the port should be set to ON position, to be able to use Automatic Data Direction Control Mode.

Under this mode, no extra code is required to control the data transferring (data transmitting and receiving), which is automatically managed with the intelligent hardware mechanism. That is, RS-485 pr ogr amming in this mode is just as simple as RS-232/RS-422 pr ogr amming.

By RTS Mode (For back-compatibility)

If the mode switch for the port is set to OFF position, By RTS Mode is used. The port is ready for transmitting data if RTS signal is asser ted and ready for receiving data if RTS signal is not asser ted.

RTS scheme is a traditional way and suitable for most system, including Windows NT, Windows 95/98 and DOS, or even UNIX, that permits RTS control from application programs. This mode should be compatible with most of the already- made RS-485 applications.

How to transmit and receive data for Windows NT, 95/98 & DOS

We recommend you to configure Industio CI-134 Series ports as follows in order to acquire precise timing control in RS-485 2-wire transmission.

4-10Industio CI-134 Series User’s Manual