User`s manual

CP-134U Series User’s Manual Serial Programming Tools
4-4
RS-485 Programming
If you intend to use your CP-134U Series board for RS-485 applications, refer to the RS-485
programming guide below, and also see the Chapter 5, “Connection Cables and Cable Wiring,” for
more details about RS-485 operation.
The CP-134U Series only supports 2-wire half-duplex RS-485 communication, in which case the
data +/- pins are used for both data transmitting and receiving, depending on the mode selected.
Moxa’s own ADDC™ (Automatic Data Direction Control) technology is used to switch between
transmitting and receiving.
ADDC™ (Automatic Data Direction Control)
ADDC™ is the best method for switching between transmission and receiving when using 2-wire
RS-485.
When using ADDC™, additional code is not required to switch between data transmitting and
receiving, since the switching mechanism is managed automatically by the board’s built-in
intelligent hardware mechanism. This means that RS-485 programming using ADDC™ mode is
just as simple and straightforward as RS-232 or RS-422 programming.