Sound Support 1 - Tandy 600 Programmer's Reference Manual

Sound
Support
The
following interrupts provide
sound
support:
INT 55h,
Function
-
Play
Tone
Entry:
AH =
(function code)
CX =
frequency
in
Hertz
DX
=
duration
in
2.5 millisecond
increments
Exit:
No
registers specified
This function
should generate
the specified
tone
for
the specified duration.
If
a tone
is
already
being
generated
when
this
function
is
called,
the current
tone should
be completed
before the
next tone
is
begun.
If
the user types
the
break key
while
sound generation
is in
progress, the
sound
should
be stopped and
control
returned
to
the
calling
program.
The Tandy 600 has only
one hardware
timer
(81C55) which
is
used
for
both playing
tones
and
setting
the
RS232
baud
rate.
The
ROM-BIOS
ignores the tone function while using the timer
as
a
baud
rate
generator.
The
tone function
is,
therefore,
only available
when
the timer
is
not
used as
a baud
rate
generator.
The
tone
function
can produce the
OHz
tone
(i.e.
Pause).
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