When selecting the handshaking to use for your terminals, printers or other devices, you have both hardware and/or software handshaking to choose from. How do you choose which to use?

Software handshaking can be either XON/XOFF or XPC. XPC is a special version of XON/XOFF designed for PC terminals. It does not use the same STOP and START codes, since the XON/XOFF stop and start codes conflict with the PC terminal definition. XPC is used with PC terminals, XON/XOFF with printers and other devices. Hardware handshaking is typically DTR/DSR on standard port boards, and is defined differently by each intelligent board. For example, the Arnet Smartport uses CTS, and the Digiboard COMxi uses DTR and CTS.

The type of handshaking you can use depends first on the type of cabling and board you are using. If you have only a three wire cable, you will only be able to use software handshaking (even that is problematical, as CCI Concurrent DOS sends out data so quickly that we may overrun a three wire cable - four wire cable is the minimum recommended). If you have at least a four wire cable, you must choose between hardware or software handshaking or both.

Using software handshaking with a very long cable may result in noise or signal reflections causing an "off" character to be sent. With XPC handshaking, that would be a "65" which can be seen in the PORTS utility with V3.04 (on earlier versions use COMS for COM1 or COM2). The issuance of this character can cause the terminal or device attached to that port to appear to be locked up. In addition, hardware handshaking is faster than software handshaking and has less overhead. However, if you are using hardware handshaking you should always have a breakout box with you for diagnostic purposes. If you have a cable with a bad pin or wire, it is extremely difficult to definitively diagnose it without a breakout box. If you have a breakout box with you, we recommend that you select hardware handshaking for all local stations and for remote stations that do not have printers. For remote stations with printers, use hardware handshaking and XPC.