From 178968cc2fc4c32fb918ebb4ccd24d78b64cd73f Mon Sep 17 00:00:00 2001
From: Javier Degirolmo
Date: Fri, 7 Oct 2011 12:17:54 -0300
Subject: Initial upload, Echo 0.8 UNSTABLE VERSION

---
 src-z80/player/pcm.z80 | 139 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 src-z80/player/pcm.z80

(limited to 'src-z80/player/pcm.z80')

diff --git a/src-z80/player/pcm.z80 b/src-z80/player/pcm.z80
new file mode 100644
index 0000000..44bc236
--- /dev/null
+++ b/src-z80/player/pcm.z80
@@ -0,0 +1,139 @@
+;****************************************************************************
+; PlayPCM*
+; Plays a PCM sample
+;****************************************************************************
+
+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:
+    call GetParam               ; Get sample ID
+
+    ld a, b
+    exx                         ; We'll modify PCM data now
+    ld b, $01                   ; Play PCM!
+
+    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                ; Restore $6000 back to HL
+    exx                         ; Back to standard variables
+
+    ld (ix+0), $2B              ; Turn on DAC
+    ld (ix+1), $80
+    ld (ix+0), $2A
+    ld (ix+1), $80
+
+    ret                         ; End of subroutine
+
+;****************************************************************************
+; UpdatePCM
+; Updates PCM output upon a timer event
+;****************************************************************************
+
+UpdatePCM:
+    ;ld (ix+0), $24              ; Reset timer
+    ;ld (ix+1), $FE
+    ;ld (ix+0), $25
+    ;ld (ix+1), $03
+    ld (ix+0), $27
+    ld (ix+1), $1F
+
+    exx                         ; Switch to PCM registers
+
+    ld a, b                     ; Do any playback?
+    or a
+    jr z, .nopcm
+
+    ld a, (RAM_LastBank)        ; Bank switch?
+    cp c
+    jp z, .noswitchu
+    ld a, c
+    ld (RAM_LastBank), a
+    BankSwitch
+.noswitchu:
+
+    ld a, (de)                  ; Get sample
+    inc a                       ; Is it end of waveform?
+    jr z, .stop                   ; If so, stop
+    ld (ix+0), $2A              ; Nope, send sample to YM2612
+    ld (ix+1), a
+
+    inc e                       ; Get address for next sample
+    jr nz, .nopcm
+    inc d
+    jr nz, .nopcm
+    ld d, $80
+    inc c
+
+.nopcm:
+    exx                         ; Go back to normal registers
+    ret                         ; End of subroutine
+
+.stop:
+    ld b, $00                   ; Stop playback
+    ld (ix+0), $2A              ; Turn off DAC
+    ld (ix+1), $80
+    ld (ix+0), $2B
+    ld (ix+1), $00
+    exx                         ; Go back to normal registers
+    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:
+    exx                         ; Stop PCM playback
+    ld b, $00
+    exx
+
+    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
-- 
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