Specifications
PC Serial
Port
Jumperlng
Three jumpers (W17, W18, and W20)
can
be used to modify
the
I/O
port address (3F8-3FFh
or
2F8-2Ffb) and interrupt usage ORQ3 or IRQ4)
of
the
PC
Serial Port. Jumper W20 se-
lects the port's
I/O
port address, while interrupt channel selection is made using either W17
or W18. Refer to Table 2-14 when
making serial channel selection.
Nota
Normally,
the
DOS
COMt
device
bas
address
3F8-3FFh
and
interrupt
IRQ4; however,
the
ROM-BIOS scans both
choices
and
will
install
the
first
one
it
finds
as
COMt
regardless
of
which option
has
been configured.
Tabla 2-14. PC Serial
Port
Configuration
I/O
ADDRESSING
INTERRUPT
W17
W18
W20
3F8h
thru
3FFh
IRQ4
short
open open
2F8h
thru
2FFh
IRQ3
open
short short
Default:
short
open open
2.4.5 V40 Serial
Port
-
J2
A
non-standard
RS232C serial port,
based
on
the V40's internal serial controller function,
appears
at
connector J2. This
port
can
be
used for connection
of
many
types
of
RS232C
serial devices. However, because this
port
is not compatible with
the
serial
ports
normally
used in PC's, off-the-shelf communications programs cannot
be used without modification.
This
port
requires the use
of
customized
or
modified software, unless it is
to
be
used
as
a
serial console device (see Chapter 3).
One
additional limitation
of
the
V40 serial port is that
it cannot
be
used in
an
interrupt
driven mode, unless
the
board's
keyboard
interrupt
is
not
required (see Chapter 4).
A single active
handshaking
signal
in
each
direction
is
available,
for
use
with
printers,
modems, and other devices, to control the flow
of
data. Consult the external serial device's
installation manual for information regarding appropriate handshake protocols,
and
other
interface considerations.
Table 2-15 gives
the
board's connector pinout and signal dermitions.
In
addition, the pins to
which each signal should
be wired for compatibility with a subset
of
the
COM
port external
serial connectors
of
PC's (DB2S) and
ATs
(DB9) is
also
indicated.
One
output signal (12-5,
DTR)
provides a means
of
sending
an
EIA
TRUE
to
the attached device,
if
needed.
In
some
applications it may
be
necessary to connect either the input handshake signal (CTS), output
handshake signal (RTS),
or
output
EIA
True
signal level
(DTR)
to
different pins
of
either
the DB2S
or
DB9 connectors than those shown in the table.
2-15