Moxa Technologies C168HS user manual Solution, Function in PComm or API-232 library. It

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	function in PComm or API-232 library. It
There is a dedicated RS-485

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

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4-18Smartio C168H/HS User’s Manual