Compaq Contec COM-2(PC)F - Manual (Page 33)

Hardware Setup
COM-2(PC)F
24
I/O Address Setting
The board is an I/O device controlled by I/O instructions from the
PC. I/O devices include expansion boards and devices inside the
PC. The various devices are identified by their I/O addresses.
I/O addresses are represented as four digit hexadecimal values
(e.g. 02A0H) and act as the ID number for each I/O device.
Most expansion boards are controlled via a range of consecutive I/O
addresses. The address of the first I/O address in the range is
called the base I/O address.
When using Enhanced mode, either 1A0H or 2A0H is selected as
the base I/O address. In Compatible mode, the fixed address for
the PC system is used.
Notes!
1. When using more than one expansion board, set each board so
that their I/O addresses do not overlap.
2. If the PC already has COM1 to COM4 ports, those ports cannot
be set for the board.