There are two types of RS-232 ports, DTE (Computer) and DCE (Modem). Connected directly together using a modem cable wired pin to pin, the inputs match the outputs of the other.
When two of the same type (DTE to DTE or DCE to DCE) are interconnected, a crossover (null modem) cable is needed to route the outputs of one to the inputs of the other. This type of cable is needed to interconnect two computers with RS-232.
RS-232 devices which require hardware handshaking require connection of RTS/CTS and/or DTR/DSR lines in order to operate properly.
Programs for RS-232 may chose to use only Receive and Transmit and ignore hardware handshaking (None) inputs, or may require connections to verify that a cable and device is ready for access.
Some devices may use Software Handshaking using Xon/Xoff characters to start and stop the incoming or outgoing data. These unprintable characters have the decimal value (17) and (19), and can often be generated in a terminal program with CTL+Q or CTL+S.
DTR Operation In RS-232 Mode
Example – DTR Operation – Select Normal (Windows 98)
In RS-232 mode, the card supports software and hardware handshaking. Set the DTR Operation driver Setting to Normal.
42 | Chapter 5 | Documentation Number 3PCIO1-0903 Manual |
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