informacje pochodza ze strony
http://en.wikipedia.org/wiki/Serial_cab ... andshaking


mowiac bardzo ogolnie " no handshaking "to kabel z trzema polaczonymi pinami. "full handshaking" ma polaczone wszystkie piny.

No handshaking
The most simplistic type of serial cable. This cable has only the data and signal ground wires connected. All of the other pins have no connection. With this type of cable flow control has to be implemented in the software. The use of this cable is restricted to data-traffic only on its cross connected Rx and Tx lines. This cable can also be used in devices that do not need or make use of modem control signals.

one end other end
(DTE) (DTE)
TxD ------------ RxD
RxD ------------ TxD
GND ------------ GND



Loop back handshaking
Because of the compatibility issues and potential problems with a simple null modem cable, a solution was developed to trick the software into thinking there was handshaking available. However, the cable pin out merely loops back and does not physically support the hardware flow control.

This cable could be used with more software but it had no actual enhancements over its predecessor. The software would work thinking it had hardware flow control but could suddenly stop when higher speeds were reached and with no identifiable reason.


Partial handshaking
In this cable the flow control lines are still looped back to the device. However, they are done so in a way that still permits Request To Send (RTS) and Clear To Send (CTS) flow control but has no actual functionality. The only way the flow control signal would reach the other device is if the opposite device checked for a Carrier Detect (CD) signal at pin 1. As a result only specially designed software could make use of this partial handshaking. Software flow control still worked with this cable.


Full handshaking
This cable is the most expensive of the serial cables because it has full wiring and pin-outs. This cable is incompatible with the previous types of cables hardware flow control, due to a crossing of its RTS/CTS pins. With this cable and the suitable software to take advantage of it, the cable is capable of much higher speeds than its predecessors. It also supports software flow control.

full handshake cable, and is used when both ends are doing hardware handshaking:

one end other end
(DTE) (DTE)
TxD ------------ RxD
RxD ------------ TxD
RTS ------------ CTS
CTS ------------ RTS
DCD -+---------- DTR
DSR -'
.....................,- DSR (musialem dopisac kropki bo ucieka do lewej)
DTR ----------+- DCD
GND ------------ GND

oznaczenia
1 DCD - Data Carrier Detect in
2 RxD - Recieve Data in
3 TxD - Transmit Data out
4 DTR - Data Terminal Ready out
5 GND - Ground -
6 DSR - Data Set Ready in
7 RTS - Request to Send out
8 CTS - Clear to Send in
9 RI