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Partial implementation of pitch envelope.
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Bobbi Webber-Manners
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30119703d3
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applecorn.po
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applecorn.po
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@ -7,6 +7,11 @@
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COUNTER DW $0000 ; Centisecond counter
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* Sound buffers
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* Four bytes are enqueued for each note, as follows:
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* - MS byte of channel number
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* - LS byte of channel number
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* - Frequency
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* - Duration
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SNDBUFSZ EQU 21 ; FOR 4 NOTES + spare byte
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SNDBUF0 DS SNDBUFSZ
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SNDBUF1 DS SNDBUFSZ
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@ -62,11 +67,31 @@ CHANENV DB $00
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DB $00
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* Envelope step counter for current note.
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* This is used in order to invoke the envelope processing at the requested
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* rate in 1/100th of a second.
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CHANCTR DB $00
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DB $00
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DB $00
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DB $00
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* Pitch envelope section (0..4)
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PITCHSECT DB $00
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DB $00
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DB $00
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DB $00
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* Step within pitch envelope section
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PITCHSTEP DB $00
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DB $00
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DB $00
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DB $00
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* Current pitch
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CURRPITCH DB $00
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DB $00
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DB $00
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DB $00
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* Get address of sound buffer
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* On entry: X is buffer number
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* On exit: A1L,A1H points to start of buffer
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@ -360,6 +385,8 @@ ENSQISR INC COUNTER+0 ; Increment centisecond timer
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BRA :S2
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:HASENV STA CHANENV,X ; Store envelope number
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STZ CHANCTR,X ; Reset envelope step counter
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STZ PITCHSECT,X ; Start on pitch section 0
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STZ PITCHSTEP,X ; Start on step 0
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LDA #$00 ; Initial amplitude is zero
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PHA ; Zero amplitude to stack
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@ -369,6 +396,7 @@ ENSQISR INC COUNTER+0 ; Increment centisecond timer
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TYA ; Duration
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STA CHANTIMES,X
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PLA ; Recover frequency
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STA CURRPITCH,X ; Store for pitch envelope
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PLY ; Recover amplitude
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JSR ENSQNOTE ; Start note playing
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:NEXT DEX
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@ -393,7 +421,8 @@ ENSQISR INC COUNTER+0 ; Increment centisecond timer
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* Handle envelope tick counter
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* On entry: X is audio channel #
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* On return: CS if this cycle is a tick, CC otherwise.
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* On return: CS if this cycle is an envelope tick, CC otherwise.
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* X is preserved
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ENVTICKS DEC CHANCTR,X ; Decrement counter
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BEQ :ZERO ; Expired
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CLC ; Not expired
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@ -405,10 +434,11 @@ ENVTICKS DEC CHANCTR,X ; Decrement counter
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* Reset envelope tick counter
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* On entry: X is audio channel #
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* On return: Sets CHANCTR,X to length of each step in 1/100ths
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RSTTICKS LDA CHANENV,X ; Get envelope number
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TAY
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JSR GETENVADDR ; Envelope address in A1L,A1H
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LDY ENVT ; Parm for length of each step
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LDY #ENVT ; Parm for length of each step
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LDA (A1L),Y ; Get value of parm
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AND #$7F ; Mask out MSB
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STA CHANCTR,X ; Reset counter
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@ -417,6 +447,7 @@ RSTTICKS LDA CHANENV,X ; Get envelope number
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* On entry: Y is envelope number
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* On return: A1L,A1H point to start of buffer for this envelope
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* X is preserved
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GETENVADDR LDA #<ENVBUF0 ; Copy ENVBUF0 to A1L,A1H
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STA A1L
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LDA #>ENVBUF0
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@ -435,15 +466,75 @@ GETENVADDR LDA #<ENVBUF0 ; Copy ENVBUF0 to A1L,A1H
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:DONE RTS
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* Process pitch envelope
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PITCHENV
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* On entry: X is audio channel #
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* X is preserved
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PITCHENV LDA CHANENV,X ; Set envelope number
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TAY
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JSR GETENVADDR ; Addr of envelope -> A1L,A1H
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LDA PITCHSECT,X ; See what section we are in
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BEQ :SECT1 ; Section 1, encoded as 0
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CMP #$01
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BEQ :SECT2 ; Section 2, encoded as 1
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CMP #$02
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BEQ :SECT3 ; Section 3, encoded as 2
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RTS ; Other section, do nothing
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:SECT1 LDY #ENVPI1 ; Parm: change pitch/step section 1
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LDA (A1L),Y ; Get value of parm
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JSR UPDPITCH ; Update the pitch
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LDY #ENVPN1 ; Parm: num steps in section 1
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LDA (A1L),Y ; Get value of parm
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CMP PITCHSTEP,X ; Are we there yet?
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BEQ :NXTSECT ; Yes!
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INC PITCHSTEP,X ; One more step
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RTS
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:SECT2 LDY #ENVPI2 ; Parm: change pitch/step section 2
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LDA (A1L),Y ; Get value of parm
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JSR UPDPITCH ; Update the pitch
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LDY #ENVPN2 ; Parm: num steps in section 2
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LDA (A1L),Y ; Get value of parm
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CMP PITCHSTEP,X ; Are we there yet?
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BEQ :NXTSECT ; Yes!
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INC PITCHSTEP,X ; One more step
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RTS
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:SECT3 LDY #ENVPI3 ; Parm: change pitch/step section 3
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LDA (A1L),Y ; Get value of parm
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JSR UPDPITCH ; Update the pitch
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LDY #ENVPN3 ; Parm: num steps in section 3
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LDA (A1L),Y ; Get value of parm
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CMP PITCHSTEP,X ; Are we there yet?
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BEQ :LASTSECT ; Yes!
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INC PITCHSTEP,X ; One more step
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RTS
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:NXTSECT INC PITCHSECT,X ; Next section
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STZ PITCHSTEP,X ; Back to step 0 of section
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RTS
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:LASTSECT BRA :NXTSECT ; TODO: HANDLE REPEATING PITCH ENVELOPES
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* Update pitch value. Called by PITCHENV.
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* On entry: A - Change of pitch/step, X is audio channel #
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* X is preserved
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UPDPITCH CLC
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ADC CURRPITCH,X ; Add change to current
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STA CURRPITCH,X ; Update
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* TODO: Update Ensoniq too!
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* Probably should have some ENSQxxx function for that
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RTS
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* Process amplitude envelope
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* On entry: X is audio channel #
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* X is preserved
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ADSRENV
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RTS
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* Update volume. Called by ADSRENV.
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* On entry: A - Change of volume/step, X is audio channel #
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* X is preserved
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UPDVOL
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RTS
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*****************************************************************************
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* Ensoniq DOC Driver for Apple IIGS Follows ...
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*****************************************************************************
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