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FUNCTION
44h
-
I/O
Control For Devices
AX
BX
CX
DX
SP:
BP;
SI:
Dl:
IP:
FLG
CS
DS
SS
ES
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
Entry
Exit
AH
=
44h
(function
code)
AL =
Request
Type
BX
=
File
handle
CX
= Number
of
byte
to
read'write
DS:DX =
Data
buffer
AX
=
status
code
if
carry set?
Request
0,1
DX
=
Device
information
Requests
2,3,4,5
AX
= number
of
bytes
transferred
Requests
6,7
AL =
device ready
status
=
not
ready
FF
=
ready
Function
44h
gets or sets device information associated
with
an
opened
handle,
or
sends/
receives
a
control string to
a
device
handle.
The
following
Request Type
values
are allowed:
1
2
3
4
5
6
7
-
Get
device
information
-
Set device
information
-
Read
from device
control
channel
-
Write
to
device
control
channel
-
Read
from
disk
device
control
channel
-
Write
to
disk
device
control
channel
-
Get
device
input status
-
Get
device output
status
This
function
can be used
to
get information
about device channels.
Calls
can be
made
upon
regular
files
as
well,
but only request
types
0, 6,
7
are
defined.
All
other
requests
return
an
invalid
function
call
error.
See
the section
on
IOCTL
strings
for
a
description
of
the control strings
which
are defined
for
each
device
in
the
system.
When
writing
the
control
string,
the
count
in
CX
gives the
number
of
bytes
in
the
string.
When
reading
a
control
string,
the
number
in
CX
is
the
maximum
number
of
bytes
to
read,
and
the
actual
number
read
will
be
returned
in
AX.
36
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