Touch Panel Support - Tandy 600 Programmer's Reference Manual

Touch
Panel
Support
—
Unsupported Software
Interrupt
The
touch panel
is
considered
to
be an
interrupt
driven device.
It
should be
scanned
for
a
change
of state at
the
same
time
that
the
keyboard
is
being
scanned.
The touch panel
is
assumed
to
have a
resolution
equal
to
the size
of
one
character
on
the
LCD
display.
Touch panel coordinates are given as row and column, which corresponds
to the
character location
on
the
LCD
which
is
being touched.
It
is
recommended
that
a touch cursor be supported which
highlights the
location currently
being touched
to
give the
user a
positive indication
of
the selected
location
on the screen.
This cursor
must be removed
from
the display
when
the
touch panel
is
not
being touched.
A
touch panel
hook
is
specified.
This
hook
should be
called
by the
BIOS whenever
it
has been
discovered
that
the touch
state of
the touch panel
has changed.
A
change
in
touch
state
occurs
when
the touch panel goes from
'not
being touched'
to
'being touched', or
from
'being
touched'
to 'not
being touched'.
If
a touch pannel
is
not
supported by
the hardware, the
following
values should be
returned:
AL =
BL =
INT
5Bh
-
Touch
Panel
Hook
Entry:
BL =
Current touch
state
=
Not touched
0FFh =
Touched
DH
= Column
at
which
state
change
occurred
DL =
Row
at
which
state
change
occurred
Exit:
No
registers specified
INT 5Bh, Function
-
Touch Panel Status
Entry:
AH =0
(function
code)
Exit:
AL =
State
change
flag
= No
change
since
last call
0FFh =
State
has
changed
since
last call
BL =
Current
state
=
Touch
panel
is
not currently being
touched
0FFh=^ Touch
panel
is
currently
being
touched
DH
= Column
at
which
state
changed
(only
if
AL =
OFFh)
DL =
Row
at
which
state
changed
(only
if
AL^OFFH)
This function
is
called
to
determine
if
the state of
the touch panel
has changed.
The
flag in
AL
indicates
if
the
touched/not touched
state
has
changed
since the last
time
this
function
was
called.
If
the
flag
in
AL
indicates that the state
has changed, then
DH-DL
should
contain the
Column-Row
at
which
that state
change
occurred.
If
a state
change
has not occurred,
then
DH-DL
are undefined.
In all
cases,
BL
indicates the current
touch
state of the
touch
panel.
182