Bar Code Reader Support - Tandy 600 Programmer's Reference Manual

Bar
Code
Reader Support
—
Unsupported
Software
Interrupt
The
data returned by the read block
function
should be
fully
decoded. There
are
a
number
of
encoding
schemes
used
with bar
code
readers,
and
the
one expected
to
be the
most
common,
or standard, for the particular
machine should be implemented.
Different
encoding
schemes can be supported by
supplying
additional
bar
code
drivers
which
the
user
may
install
as needed.
If
bar
code reader hardware
is
not
available, the bar
code
reader functions
should
return the
Device Not
Available error
code
when
called.
The
following interrupts
support bar code reader
input;
INT 5Ah, Function
-
Request Bar
Code
Reader
Entry:
AH =
(f
u notion
code)
Exit:
AL =
Standard
BIOS
error
code
This
routine
will
be
called
before
any access
to
the
bar
code
reader.
Its
purpose
is
to
mark
the
bar code
reader as
in
use.
INT 5Ah, Function
1
-
Initialize
Bar
Code
Reader
Entry:
AH =
1
(function
code)
Exit:
AL =
Standard
BIOS
error
code
This
function
is
called
before attempting
to
read bar
code
data.
It
should perform
any
initialization
necessary
to
prepare the bar
code reader
to
receive data.
INT 5Ah, Function 2
-
Read
Block
Entry:
AH =2
(function
code
CX =
buffer length
DX
=
segment
address
of
data
buffer
BX
=
offset
address
of
data
buffer
Exit:
AL=
Standard
BIOS
error
code
CX = number
of
bytes
of
data placed
in
the buffer
This function should read
a
block
of
bar
code
data
and place
it
in
the specified
buffer.
A
count
of
the
number
of
bytes transferred should
be
returned
in
CX.
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