Applecorn/mainmem.ensq.s

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2022-11-18 00:31:29 +00:00
* MAINMEM.ENSQ.S
* (c) Bobbi 2022 GPLv3
*
* Ensoniq DOC Driver for Apple IIGS.
*
* Ensoniq control registers
ENSQSNDCTL EQU $C03C
ENSQSNDDAT EQU $C03D
ENSQADDRL EQU $C03E
ENSQADDRH EQU $C03F
* Initialize Ensoniq
* Setup wavetable - one period of a square wave
* Start timer on oscillator #4, silence oscillators 0 to 3
ENSQINIT LDX #3
LDA #$80 ; Initialize sound queues
:L0 STZ SND0STARTIDX,X
STZ SND0ENDIDX,X
DEX
BNE :L0
LDA ENSQSNDCTL ; Get settings
ORA #$60 ; DOC RAM, autoincrement on
STA ENSQSNDCTL ; Set it
LDA #$00
STA ENSQADDRL ; DOC RAM addr $0000
STA ENSQADDRH ; DOC RAM addr $0000
LDA #120 ; High value of square wave
LDX #$00
:L1 STA ENSQSNDDAT ; 128 cycles of high value
INX
CPX #128
BNE :L1
LDA #80 ; Low value of square wave
:L2 STA ENSQSNDDAT ; 128 cycles of low value
INX
CPX #0
BNE :L2
LDA #$5C ; GS IRQ.SOUND initialization
STAL $E1002C
LDA #<ENSQISR
STAL $E1002D
LDA #>ENSQISR
STAL $E1002E
LDA #$00 ; Bank $00
STAL $E1002F
LDX #$E1 ; DOC Osc Enable register $E1
LDY #10 ; Five oscillators enabled
JSR ENSQWRTDOC
LDY #$00 ; Amplitude for osc #4 (timer)
LDA #33+1 ; Freq G2+1/8 tone = 99.46Hz
LDX #$04
JSR ENSQNOTE ; Start oscillator 4
LDX #$A4 ; Control register for osc #4
LDY #$08 ; Free run, with IRQ, start
JSR ENSQWRTDOC
; Fall through
* Silence all channels
ENSQSILENT LDY #$00 ; Amplitude
LDA #$80 ; Frequency
LDX #$03
:L1 JSR ENSQNOTE ; Initialize channel Y
STZ CHANTIMES,X ; No note playing
DEX
BPL :L1
RTS
* Configure an Ensoniq oscillator to play a note
* On entry: X - oscillator number 0-3 , A - frequency, Y - amplitude
* Preserves all registers
ENSQNOTE PHA
PHX
PHY
STX OSCNUM ; Stash oscillator number 0-3
PHA ; Stash orig freq
TAY
LDA FREQLOW,Y
TAY ; Frequency value LS byte
LDA #$00 ; DOC register base $00 (Freq Lo)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
PLA ; Get orig freq back
TAY
LDA FREQHIGH,Y
TAY ; Frequency value MS byte
LDA #$20 ; DOC register base $20 (Freq Hi)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
PLY ; Amplitude value
PHY
LDA #$40 ; DOC register base $40 (Volume)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
LDY #$00 ; Wavetable pointer $00
LDA #$80 ; DOC register base $80 (Wavetable)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
LDY #$00 ; Free run, no IRQ, start
LDA #$A0 ; DOC register base $A0 (Control)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
LDY #$00 ; For 256 byte wavetable
LDA #$C0 ; DOC register base $C0 (WT size)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
PLY
PLX
PLA
RTS
* Adjust frequency of note already playing
* On entry: Y - frequency to set
* Preserves X & Y
ENSQFREQ PHX
PHY ; Gonna need it again
LDA FREQLOW,Y
TAY ; Frequency value LS byte
LDA #$00 ; DOC register base $00 (Freq Lo)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
PLY ; Get freq back
PHY
LDA FREQHIGH,Y
TAY ; Frequency value MS byte
LDA #$20 ; DOC register base $20 (Freq Hi)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
PLY
PLX
RTS
* Adjust amplitude of note already playing
* On entry: Y - amplitude to set
* Preserves X & Y
ENSQAMP PHX
PHY ; Gonna need it again
LDA #$40 ; DOC register base $00 (Freq Lo)
JSR ADDOSC ; Actual register in X
JSR ENSQWRTDOC
PLY
PLX
RTS
2022-11-18 00:38:21 +00:00
**
** Private functions follow (ie: not part of driver API)
**
2022-11-18 00:31:29 +00:00
* Add oscillator number to value in A, return sum in X
* Used by ENSQNOTE & ENSQFREQ
ADDOSC CLC
ADC OSCNUM
TAX
RTS
OSCNUM DB $00
* Wait for Ensoniq to be ready
ENSQWAIT LDA ENSQSNDCTL
BMI ENSQWAIT
RTS
* Write to a DOC register
* On entry: Value in Y, register in X
* Preserves all registers
ENSQWRTDOC PHA
JSR ENSQWAIT ; Wait for DOC to be ready
LDA ENSQSNDCTL
AND #$90 ; DOC register, no autoincr
ORA #$0F ; Master volume maximum
STA ENSQSNDCTL
STX ENSQADDRL ; Select DOC register
STZ ENSQADDRH
STY ENSQSNDDAT ; Write data
PLA
RTS