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                                CHAPTER 20

                                  ______
                                  BUZZER



This chapter describes the system services which  drive  the  buzzer.   The
buzzer is driven by software, so programs calling these routines are paused
for the duration of the sound.  The buzzer volume is not  controllable  via
the operating system services.  Note that all of the following services run
with  interrupts  DISABLED  in  order  to  prevent  the  keyboard  scanning
interrupts from introducing gaps into the middle of the note.



        _______
20.0.1  BZ$ALRM


VECTOR NUMBER :         013

INPUT PARAMETERS :      NONE

OUTPUT VALUES :         NONE

DESCRIPTION

Gives the noise used by ALARM.

NOTE :  BZ$ALRM disables interrupts with an SEI.

EXAMPLE

        OS      BZ$ALRM

ERRORS

        NONE



          _______
20.0.1.1  BZ$BELL


VECTOR NUMBER :         014

INPUT PARAMETERS :      NONE

OUTPUT VALUES :         NONE

DESCRIPTION

Makes a standard beep, of fixed frequency and duration.  This is the  sound
produced by PRINT CHR$(16) in OPL, or by a call to DP$EMIT with A=16.

NOTE :  BZ$BELL disables interrupts with an SEI.

EXAMPLE

        OS      BZ$BELL

ERRORS

        NONE



            _______
20.0.1.1.1  BZ$TONE -

VECTOR NUMBER :         015

INPUT PARAMETERS :      X = duration
                        D = 1 _/ pitch

OUTPUT VALUES :         NONE

DESCRIPTION

Makes a beep of duration X milliseconds, and frequency given by the formula
:       frequency in Hz = 921600 / ( 78 + 2 * D register ), X can range from
0 to $7FFF.  X=0 produces the shortest possible note.

NOTE :  BZ$TONE disables interrupts with an SEI.

EXAMPLE

;       THIS IS THE CODE FOR BZ$BELL

        LDD     #56             ; FREQENCY = 4850 Hz
        LDX     #50             ; 50 ms
        OS      BZ$TONE

ERRORS

        NONE