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Music_DoLowHealthAlarm::
ld a, [wLowHealthAlarm]
cp DISABLE_LOW_HEALTH_ALARM
jr z, .disableAlarm
bit BIT_LOW_HEALTH_ALARM, a
ret z
and LOW_HEALTH_TIMER_MASK
jr nz, .notToneHi ;if timer > 0, play low tone.
call .playToneHi
ld a, 30 ;keep this tone for 30 frames.
jr .resetTimer
.notToneHi
cp 20
jr nz, .noTone ;if timer == 20,
call .playToneLo ;actually set the sound registers.
.noTone
ld a, CRY_SFX_END
ld [wChannelSoundIDs + CHAN5], a ;disable sound channel?
ld a, [wLowHealthAlarm]
and LOW_HEALTH_TIMER_MASK
dec a
.resetTimer
; reset the timer and enable flag.
set BIT_LOW_HEALTH_ALARM, a
ld [wLowHealthAlarm], a
ret
.disableAlarm
xor a
ld [wLowHealthAlarm], a ;disable alarm
ld [wChannelSoundIDs + CHAN5], a ;re-enable sound channel?
ld de, .toneDataSilence
jr .playTone
;update the sound registers to change the frequency.
;the tone set here stays until we change it.
.playToneHi
ld de, .toneDataHi
jr .playTone
.playToneLo
ld de, .toneDataLo
;update sound channel 1 to play the alarm, overriding all other sounds.
.playTone
ld hl, rAUD1SWEEP ;channel 1 sound register
ld c, $5
xor a
.copyLoop
ld [hli], a
ld a, [de]
inc de
dec c
jr nz, .copyLoop
ret
MACRO alarm_tone
db \1 ; length
db \2 ; envelope
dw \3 ; frequency
ENDM
;bytes to write to sound channel 1 registers for health alarm.
;starting at FF11 (FF10 is always zeroed).
.toneDataHi
alarm_tone $A0, $E2, $8750
.toneDataLo
alarm_tone $B0, $E2, $86EE
;written to stop the alarm
.toneDataSilence
alarm_tone $00, $00, $8000
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