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RTS/CTS handshake on RS232C

Posted on 1997-06-10
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Last Modified: 2010-08-05
I have developed a program in Borland C for MSDOS which handles serial communications over COM1/2/3/4 using only the pins TXD, RXD and GND. (I access the UARTs directly). I have been using Xon/Xofff software handshake but now would like to use RTS/CTS for hardware handshake. My problem is that I don't know what the standard is! What shall I do with RTS/CTS to provide data integrity?
When shall I raise and/or lower RTS?
When shall I check CTS? Do I need to check?
I would appreciate if somebody could come up with some help and maybe some documents about this subject.

Thanks in advance,

Paulo Neves
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Question by:pneves
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by:pneves
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aviad earned 50 total points
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The following is an excerpt from http://www.med2000.com:457/HANDBOOK/RTS_CTS.html
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The Ready To Send (RTS) and Clear To Send (CTS) lines for the RS-232 serial interface were originally intended as handshaking signals between a DTE device (computer, printer, and so forth) and a DCE device (almost always a modem). This section describes unidirectional handshaking between two DTE devices: a computer and a printer. The computer asserts its RTS (Ready To Send) line when it is ready to send data to the printer. The printer asserts its RTS when it was ready to receive data.

If the printer's input buffer is nearly full, it lowers its RTS line (connected to the computer's CTS (Clear To Send) line). If the computer sees CTS go low, it stops sending data until it goes high again when the printer has caught up.
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Hope this helps.
Aviad.
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