Epson 10020 - Manual (Page 140)

Note
Another way to change the real-time clock's time and date
is with the MS-DOS (version 3.3 or later) TIME and DATE
commands. See your MS-DOS Reference Manual for
instructions.
Changing Serial Port Settings
The primary and secondary serial port settings let you change
the default values for the serial port(s) in your computer. If you
are using the built-in serial port or an additional serial port you
have installed in the computer, use these options to set or
change the parameters required by the port to send and receive
data.
For example, if you have a serial printer attached to the built-in
serial port, you can use the Primary serial port option to match
the computer’s parameters to the printer’s settings. This
eliminates the need for you to use the MS-DOS MODE
command to set up the serial port when it is needed. (See the
MS-DOS Reference Manual for more information on the
MODE command.)
The primary serial port is the one that MS-DOS recognizes as
COM1 and is usually the built-in serial port. The secondary
serial port is COM2 and this is usually an additional
serial port
provided by an option card.
Note
You can reverse the assignments so the built-in port is
secondary and the optional port is primary by changing the
DIP switches on the computer and on the optional port. See
"Setting the DIP switches," above, for more information.
A-10 Changing
DIP Switches and Using Setup