196 lines
6.8 KiB
ArmAsm
196 lines
6.8 KiB
ArmAsm
* MAINMEM.ENSQ.S
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* (c) Bobbi 2022 GPLv3
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*
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* Ensoniq DOC Driver for Apple IIGS.
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*
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* Ensoniq control registers
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ENSQSNDCTL EQU $C03C
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ENSQSNDDAT EQU $C03D
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ENSQADDRL EQU $C03E
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ENSQADDRH EQU $C03F
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* Initialize Ensoniq
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* Setup wavetable - one period of a square wave
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* Start timer on oscillator #4, silence oscillators 0 to 3
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ENSQINIT LDX #3
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LDA #$80 ; Initialize sound queues
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:L0 STZ SND0STARTIDX,X
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STZ SND0ENDIDX,X
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DEX
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BNE :L0
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LDA ENSQSNDCTL ; Get settings
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ORA #$60 ; DOC RAM, autoincrement on
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STA ENSQSNDCTL ; Set it
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LDA #$00
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STA ENSQADDRL ; DOC RAM addr $0000
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STA ENSQADDRH ; DOC RAM addr $0000
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LDA #120 ; High value of square wave
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LDX #$00
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:L1 STA ENSQSNDDAT ; 128 cycles of high value
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INX
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CPX #128
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BNE :L1
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LDA #80 ; Low value of square wave
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:L2 STA ENSQSNDDAT ; 128 cycles of low value
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INX
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CPX #0
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BNE :L2
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LDA #$5C ; GS IRQ.SOUND initialization
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STAL $E1002C
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LDA #<ENSQISR
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STAL $E1002D
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LDA #>ENSQISR
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STAL $E1002E
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LDA #$00 ; Bank $00
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STAL $E1002F
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LDX #$E1 ; DOC Osc Enable register $E1
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LDY #10 ; Five oscillators enabled
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JSR ENSQWRTDOC
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LDY #$00 ; Amplitude for osc #4 (timer)
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LDA #33+1 ; Freq G2+1/8 tone = 99.46Hz
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LDX #$04
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JSR ENSQNOTE ; Start oscillator 4
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LDX #$A4 ; Control register for osc #4
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LDY #$08 ; Free run, with IRQ, start
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JSR ENSQWRTDOC
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; Fall through
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* Silence all channels
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ENSQSILENT LDY #$00 ; Amplitude
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LDA #$80 ; Frequency
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LDX #$03
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:L1 JSR ENSQNOTE ; Initialize channel Y
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STZ CHANTIMES,X ; No note playing
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DEX
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BPL :L1
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RTS
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* Configure an Ensoniq oscillator to play a note
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* On entry: X - oscillator number 0-3 , A - frequency, Y - amplitude
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* Preserves all registers
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ENSQNOTE PHA
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PHX
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PHY
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STX OSCNUM ; Stash oscillator number 0-3
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PHA ; Stash orig freq
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TAY
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LDA EFREQLOW,Y
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TAY ; Frequency value LS byte
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LDA #$00 ; DOC register base $00 (Freq Lo)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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PLA ; Get orig freq back
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TAY
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LDA EFREQHIGH,Y
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TAY ; Frequency value MS byte
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LDA #$20 ; DOC register base $20 (Freq Hi)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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PLY ; Amplitude value
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PHY
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LDA #$40 ; DOC register base $40 (Volume)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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LDY #$00 ; Wavetable pointer $00
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LDA #$80 ; DOC register base $80 (Wavetable)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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LDY #$00 ; Free run, no IRQ, start
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LDA #$A0 ; DOC register base $A0 (Control)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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LDY #$00 ; For 256 byte wavetable
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LDA #$C0 ; DOC register base $C0 (WT size)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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PLY
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PLX
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PLA
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RTS
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* Adjust frequency of note already playing
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* On entry: X - oscillator number 0-3, Y - frequency to set
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* Preserves X & Y
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ENSQFREQ PHX
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PHY ; Gonna need it again
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LDA EFREQLOW,Y
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TAY ; Frequency value LS byte
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LDA #$00 ; DOC register base $00 (Freq Lo)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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PLY ; Get freq back
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PHY
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LDA EFREQHIGH,Y
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TAY ; Frequency value MS byte
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LDA #$20 ; DOC register base $20 (Freq Hi)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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PLY
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PLX
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RTS
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* Adjust amplitude of note already playing
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* On entry: X - oscillator number 0-3, Y - amplitude to set
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* Preserves X & Y
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ENSQAMP PHX
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PHY ; Gonna need it again
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LDA #$40 ; DOC register base $00 (Freq Lo)
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JSR ADDOSC ; Actual register in X
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JSR ENSQWRTDOC
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PLY
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PLX
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RTS
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* Ensoniq interrupt service routine - just calls generic audio ISR
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ENSQISR CLD
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JSR AUDIOISR
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RTL
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**
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** Private functions follow (ie: not part of driver API)
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**
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* Add oscillator number to value in A, return sum in X
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* Used by ENSQNOTE & ENSQFREQ
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ADDOSC CLC
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ADC OSCNUM
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TAX
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RTS
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OSCNUM DB $00
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* Wait for Ensoniq to be ready
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ENSQWAIT LDA ENSQSNDCTL
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BMI ENSQWAIT
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RTS
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* Write to a DOC register
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* On entry: Value in Y, register in X
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* Preserves all registers
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ENSQWRTDOC PHA
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JSR ENSQWAIT ; Wait for DOC to be ready
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LDA ENSQSNDCTL
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AND #$90 ; DOC register, no autoincr
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ORA #$0F ; Master volume maximum
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STA ENSQSNDCTL
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STX ENSQADDRL ; Select DOC register
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STZ ENSQADDRH
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STY ENSQSNDDAT ; Write data
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PLA
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RTS
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