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INT 59h, Function
E
-
Get
Serial
Device
Control Status
Entry:
AH
= E
(function
code)
Exit:
AL =
State
of control lines
Bit
-
CTS
1
-DSR
2
-CD
3-7
-
reserved
for
future
use
This
function
is
used
to test
the
state of
the
serial
handshaking
lines.
INT 59h,
Function F
-
Select Active
Serial
Device
Entry:
AH
=
F
(function
code)
AL =
Device
number
to
select
Exit:
AL=
Standard
BIOS
error
code
This
function specifies
which
serial
device
is
active.
The
functions
for
configuring,
reading
from
and
writing to serial
device
affect
the active
port.
INT 59h, Function
10h
-
Request
Serial
Device
Entry:
AH
=
10h
(function
code)
AL
=
Device
number
to
attach
Exit:
AL=
Standard
BIOS
error
code
This
function
will
be
called
before
accessing a
serial
device.
It
does
not select the device, but
marks
it
as
being
in
use.
Attempting
to
select
a
serial
device
via function
OFh
before
attaching
it
via
this
function
is
an
error.
INT 59h, Function
11
h
-
Release
Serial
Device
Entry:
AH
=
1
1
h (function
code)
AL=
Device
number
to
release
Exit:
AL=
Standard
BIOS
error
code
This
function
code
is
called
after
an
application
is
finished
using
a
serial
device.
This
function
marks
the specified
device
as
not
in
use. This
call
does
not
affect
which
serial
device
is
currently selected.
179
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