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Moxa Technologies CP-114 Series User Manual

Page 40

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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.