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SERVSWITCH™ WIZARD MULTIMEDIA KVM EXTENDER
5.11 RS-232 Serial Support
The ServSwitch Wizard Multimedia KVM Extender is designed to carry
bidirectional communication between
one
RS-232 serial device or port attached to
its Unit A and
one
such device or port attached to its Unit B. Unlike the way it
handles other I/O, the Extender doesn’t perform serial switching or contention:
Even when the primary control station’s keyboard and mouse are not in control of
the primary CPU—and for that matter, even when the primary station is locked or
selects “CPU zero”—local
↔
remote serial communication will continue
uninterrupted. So if your application calls for serial switching or contention, it will
have to be handled by some other device.
The default data rate for the Extender’s serial link is 1200 bps, which is suitable
for serial mice. Its default protocol/handshaking setting is also for a serial mouse.
That having been said, we strongly recommend using a PS/2 mouse rather than a
serial mouse; see
Section 4.3
.
9600 bps, the other possible data rate, will be better for most kinds of
communication, including PC-to-PC and PC-to-printer. Keep in mind that any
serial devices you attach to the Extender must be asynchronous, because the
Extender doesn’t support the RS-232 synchronous clock signals.
The second possible handshaking setting is “hardware.” In this setting, the
Extender “passes through” hardware flow control this way: When either Unit
detects a high input level on its DTR lead (Data Terminal Ready, Pin 4), it signals
the other Unit to raise its DSR and CTS leads (Data Set Ready and Clear to Send,
Pins 6 and 8—which are electrically connected inside the Extender). This means
that if you have two CPU serial ports or other DTEs communicating through the
Extender, they can hardware-flow-control each other even if they’re both attached
to the Extender with standard, straight-though-pinned cables.
The third available handshaking setting is “none.” In this setting, the Extender
ignores the states of the control signals. This is ideal for continuous uncontrolled
transmissions or for applications that use X-ON/X-OFF or other types of software
flow control. However, the data rate is limited to 1200 bps in this setting.
You can also set the Extender’s data format. The default format is 7 data bits, no
parity, and one stop bit, but alternative settings include 8 data bits, even or odd
parity, and two stop bits.