dos33fsprogs/music/tiny_music/mockingboard_setup.s
2021-11-04 17:19:21 -04:00

244 lines
6.2 KiB
ArmAsm

; Mockingboad programming:
; + Has two 6522 I/O chips connected to two AY-3-8910 chips
; + Optionally has some speech chips controlled via the outport on the AY
; + Often in slot 4
; TODO: how to auto-detect?
; References used:
; http://macgui.com/usenet/?group=2&id=8366
; 6522 Data Sheet
; AY-3-8910 Data Sheet
;========================
; Mockingboard card
; Essentially two 6522s hooked to the Apple II bus
; Connected to AY-3-8910 chips
; PA0-PA7 on 6522 connected to DA0-DA7 on AY
; PB0 on 6522 connected to BC1
; PB1 on 6522 connected to BDIR
; PB2 on 6522 connected to RESET
; left speaker
MOCK_6522_ORB1 = $C400 ; 6522 #1 port b data
MOCK_6522_ORA1 = $C401 ; 6522 #1 port a data
MOCK_6522_DDRB1 = $C402 ; 6522 #1 data direction port B
MOCK_6522_DDRA1 = $C403 ; 6522 #1 data direction port A
MOCK_6522_T1CL = $C404 ; 6522 #1 t1 low order latches
MOCK_6522_T1CH = $C405 ; 6522 #1 t1 high order counter
MOCK_6522_T1LL = $C406 ; 6522 #1 t1 low order latches
MOCK_6522_T1LH = $C407 ; 6522 #1 t1 high order latches
MOCK_6522_T2CL = $C408 ; 6522 #1 t2 low order latches
MOCK_6522_T2CH = $C409 ; 6522 #1 t2 high order counters
MOCK_6522_SR = $C40A ; 6522 #1 shift register
MOCK_6522_ACR = $C40B ; 6522 #1 auxilliary control register
MOCK_6522_PCR = $C40C ; 6522 #1 peripheral control register
MOCK_6522_IFR = $C40D ; 6522 #1 interrupt flag register
MOCK_6522_IER = $C40E ; 6522 #1 interrupt enable register
MOCK_6522_ORANH = $C40F ; 6522 #1 port a data no handshake
; right speaker
MOCK_6522_ORB2 = $C480 ; 6522 #2 port b data
MOCK_6522_ORA2 = $C481 ; 6522 #2 port a data
MOCK_6522_DDRB2 = $C482 ; 6522 #2 data direction port B
MOCK_6522_DDRA2 = $C483 ; 6522 #2 data direction port A
; AY-3-8910 commands on port B
; RESET BDIR BC1
MOCK_AY_RESET = $0 ; 0 0 0
MOCK_AY_INACTIVE = $4 ; 1 0 0
MOCK_AY_READ = $5 ; 1 0 1
MOCK_AY_WRITE = $6 ; 1 1 0
MOCK_AY_LATCH_ADDR = $7 ; 1 1 1
;========================
;========================
; Mockingboard Init
;========================
;========================
mockingboard_init:
;=========================
; Initialize the 6522s
; set the data direction for all pins of PortA/PortB to be output
lda #$ff ; all output (1)
sta MOCK_6522_DDRB1 ; set for 6522 #1
sta MOCK_6522_DDRA1
sta MOCK_6522_DDRB2 ; set for 6522 #2
sta MOCK_6522_DDRA2
mockingboard_setup_interrupt:
;=========================
; Setup Interrupt Handler
;=========================
; NOTE: we don't support IIc as it's a hack
; traditionally Mockingboard on IIc was rare
;========================
; set up interrupt
; Vector address goes to 0x3fe/0x3ff
lda #<interrupt_handler
sta $03fe
lda #>interrupt_handler
sta $03ff
;============================
; Enable 50Hz clock on 6522
;============================
; Note, on Apple II the clock isn't 1MHz but is actually closer to
; roughly 1.023MHz, and every 65th clock is stretched (it's complicated)
; 9c40 / 1.023e6 = .040s, 25Hz
; 8534 / 1.023e6 = .033s, 30Hz
; 4fe7 / 1.023e6 = .020s, 50Hz
; 411a / 1.023e6 = .016s, 60Hz
; French Touch uses
; 4e20 / 1.000e6 = .020s, 50Hz, which assumes 1MHz clock freq
sei ; disable interrupts just in case
lda #$40 ; Continuous interrupts, don't touch PB7
sta MOCK_6522_ACR ; ACR register
lda #$7F ; clear all interrupt flags
sta MOCK_6522_IER ; IER register (interrupt enable)
lda #$C0
sta MOCK_6522_IFR ; IFR: 1100, enable interrupt on timer one oflow
sta MOCK_6522_IER ; IER: 1100, enable timer one interrupt
lda #$34
; lda #$E7
sta MOCK_6522_T1CL ; write into low-order latch
lda #$85
; lda #$4f
sta MOCK_6522_T1CH ; write into high-order latch,
; load both values into counter
; clear interrupt and start counting
;===================================
;===================================
; Reset Both AY-3-8910s
;===================================
;===================================
;===========================
; Reset Right/Left AY-3-8910
;===========================
lda #MOCK_AY_RESET
sta MOCK_6522_ORB1
sta MOCK_6522_ORB2
lda #MOCK_AY_INACTIVE
sta MOCK_6522_ORB1
sta MOCK_6522_ORB2
init_registers:
; init song data
lda #0
sta SONG_OFFSET
sta SONG_COUNTDOWN
; read 14 bytes from beginning of song to init
ldx #13
init_loop:
init_smc:
txa
tay
lda (SONG_L),Y
jsr ay3_write_reg ; trashes Y
dex
bne init_loop
; update SONG_L to point past the init
lda SONG_L
clc
adc #14
sta SONG_L
bcc no_oflo
inc SONG_H
no_oflo:
; create Frequency Table
ldx #12
make_freq_loop:
lda frequency_lookup,X
lsr
sta frequency_lookup+16,X
lsr
sta frequency_lookup+32,X
dex
bpl make_freq_loop
rts
;=====================
;=====================
;=====================
; ay3 write reg
;=====================
;=====================
;=====================
; writes to both chips (so same output to both Right/Left)
; address in X (preserved)
; value in A
; NOTE: it looks like you could interleave things to save bytes
; but technically this violates the AY-3-8910 spec sheet on
; finishing accesses in less than 10us (10 cycles)
ay3_write_reg:
pha
lda #MOCK_AY_LATCH_ADDR ; latch_address for PB1 ; 2
ldy #MOCK_AY_INACTIVE ; go inactive ; 2
stx MOCK_6522_ORA1 ; put address on PA1 ; 4
sta MOCK_6522_ORB1 ; latch_address on PB1 ; 4
sty MOCK_6522_ORB1 ; 4
stx MOCK_6522_ORA2 ; put address on PA2 ; 4
sta MOCK_6522_ORB2 ; latch_address on PB2 ; 4
sty MOCK_6522_ORB2 ; 4
pla
; value
sta MOCK_6522_ORA1 ; put value on PA1 ; 4
sta MOCK_6522_ORA2 ; put value on PA2 ; 4
lda #MOCK_AY_WRITE ; ; 2
sta MOCK_6522_ORB1 ; write on PB1 ; 4
sty MOCK_6522_ORB1 ; 4
sta MOCK_6522_ORB2 ; write on PB2 ; 4
sty MOCK_6522_ORB2 ; 4
rts
; starts at C4
frequency_lookup:
.byte $F4,$E6,$D9,$CD,$C1,$B7,$AC,$A3,$99,$91,$89,$81,$00
;.byte $00,$00,$00,$00
;.byte $7A,$73,$6C,$66,$60,$5B,$56,$51,$4C,$48,$44,$40,$00,$00,$00,$00
;.byte $3D,$39,$36,$33,$30,$2D,$2B,$28,$26,$24,$22,$20,$00,$00,$00,$00