Moxa Technologies CP-114 Series - Manual (Page 40)

4-8 Industio CP-114 User's Manual
There are 2 solutions to control RS-485 2-wire transmission.
Solution 1
The following model is common in RS-485 2-wire transmission.
sio_SetWriteTimeouts(port, 0); /* Set sio_write() into block mode if for Windows NT
and Windows 95/98 */
sio_RTS(port, 1); /* Turn on RTS signal. The RS-485 port is ready for
transmitting data. */
sio_write(port, buff, 10); /* Write 10 byte characters in "buff". The function
blocks until last character transmitted */
sio_RTS(port, 0); /* Turn off RTS signal. The RS-485 port is ready for
receiving data. */
sio_read(port, buff, 10); /* Read 10 bytes */
Solution 2
There is a dedicated RS-485 function in PComm or API-232 library. It integrates the above
functions of solution 1 regarding sending data as one.
sio_putb_x(port, buff, tick ); /* 1. Turn on RTS and ready for transmitting data.
2. Send data.
3. Wait for tick time.
4. Turn off RTS and ready for receiving data. */
For more information on these functions, please refer to PComm library on-line Help file for
Windows NT and Windows 95/98 or API-232.txt file for DOS, respectively.