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INT
59h,
Function
A
-
Transmit Data
Entry:
AH
= A
(function
code)
AL
=
data
to
transmit
Exit;
AL=
Standard
BIOS
error
code
It
is
recommended
that
a
timeout
be
associated
with
the
transmitter
for failsafe
reasons.
If
the
transmitter
does
not
become
ready
to
accept
the character
within
the timeout period,
then
an
error
should
be
returned.
The recommended
timeout period
is
250
msec.
INT
59h,
Function
B
-
Transmit Break
Entry;
AH
=
B
(function
code)
Exit:
AL=
Standard
BIOS
error
code
INT 59h,
Function
C
-
Configure
Modem
Entry:
AH
=
C
(function
code)
CH
=
data
rate
1
=300
baud
3
=
1
200 baud
CL
=
mode
=
originate
0FFh =
answer
Exit:
AL=
Standard
BIOS
error
code
The
data
rate
parameter
specified
in
CH
specifies the
encoding
method
to
use.
Note: For
all
of
the
above
routines,
when
an
error
is
returned the
BIOS
must
clear
its
error status
so subsequent
calls
will
only
return
an
error
if
a
new
error
has
occurred.
INT 59h, Function
D
-
Set
Serial
Control Lines
Entry:
AH
=
D
(function
code)
AL =
State
to set control
lines
Bit
-
RTS
1
-DTR
2-7
-
reserved
for future
use
Exit:
No
registers specified
This
function
is
used
to
set the
serial
handshaking
lines to
a
specified
state.
A
zero
in
a
bit
position
means
to
set
the
corresponding
control
line
to
a
spacing
(0)
state,
a
one
bit
means
to
set
the
corresponding
control
line
to
the
marking
(1)
state.
178
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