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|
;****************************************************************************
; UpdatePCM
; Updates PCM output upon a timer event
;****************************************************************************
UpdatePCM:
ret ; $C9 = RET = no PCM playback
; $D0 = RET NC = PCM playback
exx ; Switch to PCM registers
.doagain:
ld (ix+0), $27 ; Acknowledge timer
ld (ix+1), $1F
ld a, (hl) ; Fetch next sample
inc a ; Check if it's the end of the waveform
jr z, .stop
ld (ix+0), $2A ; Nope, send sample to YM2612
ld (ix+1), a
inc l ; Update buffer position
jr z, .reload ; Need to buffer more?
.nopcm:
exx ; Switch to normal registers
ret ; End of subroutine
.stop:
ld a, $C9 ; Stop playback
ld (UpdatePCM), a
ld (ix+0), $2A ; Turn off DAC
ld (ix+1), $80
ld (ix+0), $2B
ld (ix+1), $00
exx ; Switch to normal registers
ret ; End of subroutine
.reload:
ld a, (RAM_LastBank) ; Bank switch if needed
cp c
jp z, .noswitchu
ld a, c
ld (RAM_LastBank), a
ld hl, $6000
BankSwitch
.noswitchu:
ld hl, RAM_PCMBuffer ; Load samples into the buffer
ld a, c
ex de, hl
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ldi
ex de, hl
ld c, a
ld a, e
or a
jp nz, .nobankchg ; Update high bytes of address if needed
inc d
jp nz, .nobankchg
ld d, $80
inc c
.nobankchg:
ld l, RAM_PCMBuffer&$FF ; Go back to the beginning of the buffer
jp .doagain ; We took so long we should play the next
; sample already ._.'
;****************************************************************************
; PlayPCM* [event $0C]
; Plays a PCM sample
;----------------------------------------------------------------------------
; input c .... current bank
; input hl ... current address
;----------------------------------------------------------------------------
; breaks: af, b
;****************************************************************************
PlayPCMSFX:
call PlayPCM ; We're just a wrapper
jp ProcessSFXRun ; End of subroutine
PlayPCMBGM:
PollPCM
ld a, (RAM_Locked+6) ; Check if channel is free
or a
jp nz, ProcessBGMSkip1 ; Don't play sample if locked
call PlayPCM ; We're just a wrapper
jp ProcessBGMRun ; End of subroutine
PlayPCM:
ld a, (RAM_GlobalVol+$0C) ; Are we allowed to play PCM?
or a
ret z
call GetParam ; Get sample ID
ld a, b
exx ; We'll modify PCM data now
ld h, RAM_PointerList>>8 ; Get offset in pointer list
ld l, a
ld d, (hl) ; Get PCM address
inc h
ld e, (hl)
inc h
ld c, (hl)
ld hl, $6000 ; Initial bank switch
ld a, c
ld (RAM_LastBank), a
BankSwitch
ld h, RAM_PCMBuffer>>8 ; Set buffer where the sample starts
ld a, e
or $F0
ld l, a
ld b, l
.load1st: ; Copy initial samples into the buffer
ld a, (de)
ld (hl), a
inc e
inc l
jp nz, .load1st
ld l, b
ld a, e ; Check if the sample should skip ahead
or a ; already
jp nz, .noskip1st
inc d
jp nz, .noskip1st
ld d, $80
inc c
.noskip1st:
exx ; Back to standard registers
ld a, $D0 ; Enable PCM playback
ld (UpdatePCM), a
ld (ix+0), $2B ; Turn on DAC
ld (ix+1), $80
ld (ix+0), $2A
ld (ix+1), $80
ret ; End of subroutine
;****************************************************************************
; StopPCM*
; Stops a PCM sample
;****************************************************************************
StopPCMSFX:
call StopPCM ; We're just a wrapper
jp ProcessSFXRun ; End of subroutine
StopPCMBGM:
PollPCM
ld a, (RAM_Locked+6) ; Check if channel is free
or a
jp nz, ProcessBGMRun ; Don't stop sample if locked
call StopPCM ; We're just a wrapper
jp ProcessBGMRun ; End of subroutine
StopPCM:
ld a, $C9 ; Stop PCM playback
ld (UpdatePCM), a
ld (ix+0), $2B ; Disable DAC
ld (ix+1), $00
ret ; End of subroutine
;****************************************************************************
; LockChannelPCM [event $EC]
; Locks the PCM channel
;****************************************************************************
LockChannelPCM:
ld a, $01 ; Lock PCM channel
ld (RAM_Locked+6), a
call StopPCM ; Stop PCM playback
jp ProcessSFXRun ; End of subroutine
;****************************************************************************
; SetPCMRate [command $07]
; Changes the sample rate of PCM
;****************************************************************************
SetPCMRate:
ld a, (RAM_ComBank) ; Get new rate
cpl
ld b, a
xor a ; Parsed command already
ld (RAM_Command), a
ld a, b ; Set high bits of timer
ld (ix+0), $24
rrca
rrca
or $C0
ld (ix+1), a
ld a, b ; Set low bits of timer
ld (ix+0), $25
and $03
ld (ix+1), a
jp IdleLoop ; End of subroutine
|
