;******************************************************************************* ; UpdateFmChan ; ; Called every tick (after the tracks are updated) to update a YM2612 channel. ; It looks at the attached track's state and writes to the hardware whatever has ; changed since the last update. ;------------------------------------------------------------------------------- ; input iy .... pointer to FM channel state ;------------------------------------------------------------------------------- ; modifies .... all but iy ;******************************************************************************* UpdateFmChan: ld h, YmAddr1>>8 ; We're going to access the YM2612 ; through HL. Sometimes we need to ; change which port to access but ; the upper byte of the address stays ; the same, so put it into H now. ld e, (iy+FMCHAN_TRACK) ; Get pointer to the track associated call GetTrackStateAddr ; with this channel ld a, (ix+TRACK_FLAGS) ; Get flags rrca ; Is keying canceled? jr c, NoFmKeyOff ; If so, skip this rrca ; Requested key-off? ld a, $00 ; Mask = all slots off call c, DoFmKey ; If so, do key-off NoFmKeyOff: ld l, (iy+FMCHAN_PORT) ; The following stuff is done on ; different banks depending on ; which channel it is bit FLAG_INSTRUMENT,(ix+TRACK_FLAGS); Need to load new instrument? call nz, LoadFmVoice bit FLAG_VOLUME, (ix+TRACK_FLAGS) ; Need to recompute TL values? call nz, UpdateFmVol bit FLAG_PITCH, (ix+TRACK_FLAGS) ; Need to recompute frequency? call nz, UpdateFmFreq bit FLAG_PAN, (ix+TRACK_FLAGS) ; Need to update panning? call nz, UpdateFmPan ld a, (ix+TRACK_FLAGS) ; Get flags rrca ; Is keying canceled? jr c, NoFmKeyOn ; If so, skip this rrca ; Skip key-off flag rrca ; Requested key-on? ld a, $F0 ; Mask = all slots on call c, DoFmKey ; If so, do key-on NoFmKeyOn: ld (ix+TRACK_FLAGS), 0 ; Acknowledge all the flags ret ; Done with this channel ;******************************************************************************* ; DoFmKey ; Performs key-on/off for a FM channel. ;------------------------------------------------------------------------------- ; input iy .... pointer to FM channel state ; input h ..... pointer to YmAddr1 (upper byte) ; input a ..... $00 = key-off, $F0 = key-on ;------------------------------------------------------------------------------- ; output hl ... pointer to YmAddr1 ;------------------------------------------------------------------------------- ; modifies .... a,hl ;******************************************************************************* DoFmKey: ld l, YmAddr1&$FF ; Key is always done in bank 1 ; regardless of channel ld (hl), YMREG_KEY ; Write register number or (iy+FMCHAN_KEY) ; OR mask with the channel bits inc hl ld (hl), a ; Write register value dec hl ret ; End of subroutine ;******************************************************************************* ; LoadFmVoice ; Called by the FM update code to load a new FM instrument. Slow!! ;------------------------------------------------------------------------------- ; input ix .... pointer to track state ; input iy .... pointer to FM channel state ; input hl .... pointer to YmAddr1 for ch1-ch3 ; pointer to YmAddr2 for ch4-ch6 ;------------------------------------------------------------------------------- ; modifies .... a,bc,de,bc',de',hl' ;******************************************************************************* LoadFmVoice: ; register usage because this subroutine is a mess: ; ; a = scratch ; b = loop counter ; c = register number ; hl = pointer to YM2612 port ; ix = pointer to track state ; iy = pointer to FM channel state ; bc' = scratch (stomped on by LDI) ; de' = pointer to instrument ; hl' = scratch (used as pointer) set FLAG_VOLUME, (ix+TRACK_FLAGS) ; TL registers need to be recomputed ; as well but we won't touch them, ; request the volume code do that exx call GetTrackInstrument ; Get pointer to the instrument data exx ld a, YMREG_MUL ; Get base register number for this add a, (iy+FMCHAN_BASE) ; FM channel ld c, a add a, YMREG_ALGO-YMREG_MUL ; Algorithm register number ld (hl), a ; Write register number exx ld a, (de) ; Get algorithm and feedback inc de ; Advance address exx inc hl ld (hl), a ; Write algorithm and feedback dec hl and $07 ; Isolate algorithm alone exx add a, InstrumentTLMask&$FF ; Retrieve the bitmask of which ld l, a ; slots have their TL affected by adc a, InstrumentTLMask>>8 ; attenuation and store it in the sub l ; channel state ld h, a ld a, (hl) ld (iy+FMCHAN_TLMASK), a exx ld b, 4 ; Write MUL/DT registers call LoadFmVoice_Loop exx push iy ; Copy the TL values into the FM pop hl ; channel state, they'll be written ex de, hl ; later by the attenuation code ldi ldi ldi ldi ex de, hl exx ld a, YMREG_AR-YMREG_TL ; Adjust the register number to account add a, c ; for the skipped writes from above ld c, a ld b, 20 ; Write remaining registers LoadFmVoice_Loop: exx ld a, (de) ; Get next value to write inc de ; Advance address exx ld (hl), c ; Write register number inc hl ld (hl), a ; Write register dec hl inc c ; Increment register number inc c inc c inc c djnz LoadFmVoice_Loop ; Go for next register ret ; End of subroutine ;******************************************************************************* ; UpdateFmVol ; ; Recomputes the TL registers for a FM channel to apply the track's attenuation. ; The actual values depend on the current instrument (the FM channel state keeps ; track of the required information). ;------------------------------------------------------------------------------- ; input ix .... pointer to track state ; input iy .... pointer to FM channel state ; input hl .... pointer to YmAddr1 for ch1-ch3 ; pointer to YmAddr2 for ch4-ch6 ;------------------------------------------------------------------------------- ; modifies .... a,bc,de,bc',de',hl' ;******************************************************************************* UpdateFmVol: push iy ; Get pointer to all TL values for pop de ; the current instrument ld a, YMREG_TL ; Determine register number for the add a, (iy+FMCHAN_BASE) ; TL values for this channel ld c, a exx ld e, (iy+FMCHAN_TLMASK) ; Mask of which TL values to change ld b, (ix+TRACK_VOLUME) ; Get attenuation from track ld c, $7F ; Maximum allowed value for TL exx ld b, 4 ; Loop through all slots UpdateFmVolLoop: ld a, (de) ; Get base TL value for this slot inc de ; (for attenuation = 0) exx rr e ; Should we touch this TL value? jr nc, UpdateFmVolOk ; If not, leave it as-is add a, b ; Add attenuation from track cp c ; Is it too quiet? jr c, UpdateFmVolOk ; If not, use result as-is ld a, c ; If yes, make it mute instead UpdateFmVolOk: exx ld (hl), c ; Write register number inc hl ld (hl), a ; Write new TL value dec hl inc c ; Next register number (and burn a inc c ; few cycles meanwhile) inc c inc c djnz UpdateFmVolLoop ; Go for next slot ret ; End of subroutine ;******************************************************************************* ; UpdateFmFreq ; Recomputes and updates the frequency for a YM2612 channel. ;------------------------------------------------------------------------------- ; input ix .... pointer to track state ; input iy .... pointer to FM channel state ; input hl .... pointer to YmAddr1 for ch1-ch3 ; pointer to YmAddr2 for ch4-ch6 ;------------------------------------------------------------------------------- ; modifies .... a,bc,de,bc',de',hl' ;******************************************************************************* UpdateFmFreq: ld a, YMREG_FREQ_HI ; Get register number for the frequency add a, (iy+FMCHAN_BASE) ; values for this channel ld b, a exx ; We'll work on the alternate registers call GetTrackPitch ; Get pitch to use ; A = semitone ; C = octave ld hl, FmFreqTable ; Get frequency for this semitone call GetWordFromList ; into HL ld a, c ; Get octave add a, a ; Put octave bits where they belong add a, a add a, a or h ; Merge with upper bits of frequency exx ; Back to normal registers ld (hl), b ; Write register number inc hl ld (hl), a ; Write upper byte of frequency dec hl exx ; Get lower byte of frequency ld a, l exx dec b ; Get register number for low byte dec b ; of frequency (and help burn a few dec b ; more cycles we need) dec b push hl ; Still not slow enough... pop hl ld (hl), b ; Write register number inc hl ld (hl), a ; Write lower byte of frequency dec hl ret ; End of subroutine ;******************************************************************************* ; UpdateFmPan ; Updates the pan setting for a YM2612 channel. ;------------------------------------------------------------------------------- ; input ix .... pointer to track state ; input iy .... pointer to FM channel state ; input hl .... pointer to YmAddr1 for ch1-ch3 ; pointer to YmAddr2 for ch4-ch6 ;------------------------------------------------------------------------------- ; modifies .... a ;******************************************************************************* UpdateFmPan: ld a, YMREG_PAN ; Get register number to write add (iy+FMCHAN_BASE) ld (hl), a ; Write register number ld a, (ix+TRACK_PAN) ; Get new pan setting inc hl ld (hl), a ; Write new pan setting dec hl ret ; End of subroutine ;******************************************************************************* ; MuteFm ; Mutes all the FM channels immediately. This modifies the instruments on the ; hardware side but not the FM state side, to resume playback make sure to mark ; the FLAG_INSTRUMENT flag and call UpdateFmChan to reload the instrument. ;------------------------------------------------------------------------------- ; modifies ... all ;******************************************************************************* MuteFm: ld hl, YmAddr2 ; Set up RR of ch4-ch6 call MuteFmRR ld l, YmAddr1&$FF ; Set up RR of ch1-ch3 call MuteFmRR ld bc, 7<<8 ; B = loop counter ; C = channel to key-off MuteFmKeyLoop: ld (hl), YMREG_KEY ; Write register number inc hl ; Point to data port ld (hl), c ; Tell it to key-off this channel dec hl ; Point back to address port ex (sp), hl ; Waste a lot of cycles (we need 80 ex (sp), hl ; cycles in total, including the ex (sp), hl ; DEC HL, INC C and DJNZ) ex (sp), hl inc c ; Increase channel number djnz MuteFmKeyLoop ; Go for next channel ret ; End of subroutine ;------------------------------------------------------------------------------- MuteFmRR: ld bc, (16<<8)|YMREG_RR ; B = loop counter ; C = register number MuteFmRRLoop: ld (hl), c ; Write register number inc hl ; Point to data port ld (hl), $0F ; Write register value (max. RR) dec hl ; Point back to address port push hl ; Waste a few cycles pop hl inc c ; Increase register number djnz MuteFmRRLoop ; Go write next RR register ret ; Back to subroutine