RSX280 now supports 4 additional terminals on Bill Shen's quad-serial port
board (OX16C954 chip). If the quad-serial board is not detected when the
system is booted up, the corresponding units will be set off-line.

The current version of the driver initializes all four ports to 19200 baud,
8-N-1.

Important:
----------

For the OX16C954 chip to work properly, any unused receiver input lines must
*not* be left floating (unconnected), despite what the chip documentation says.
The receiver inputs are very sensitive to noise and hum pickup, and thus are
prone to flooding the system with spurious characters when unconnected.

Thus, I'd recommend soldering a 1K..10K resistor from the receiver input lines
to ground (see accompanying picture quad-serial-resistors-1.jpg). The resistors
will keep the noise out by grounding the input lines when not used, and will
not interfere with normal operation.

