dos33fsprogs/megademo/mockingboard.s

210 lines
5.3 KiB
ArmAsm

; ZP addresses
; left channel
MOCK_6522_1_ORB = $C400 ; 6522 #1 port b data
MOCK_6522_1_ORA = $C401 ; 6522 #1 port a data
MOCK_6522_1_DDRB = $C402 ; 6522 #1 data direction port B
MOCK_6522_1_DDRA = $C403 ; 6522 #1 data direction port A
MOCK_6522_1_T1C_L = $C404 ; 6522 #1 Low-order counter
MOCK_6522_1_T1C_H = $C405 ; 6522 #1 High-order counter
MOCK_6522_1_T1L_L = $C406 ; 6522 #1 Low-order latch
MOCK_6522_1_T1L_H = $C407 ; 6522 #1 High-order latch
MOCK_6522_1_T2C_L = $C408 ; 6522 #1 Timer2 Low-order Latch/Counter
MOCK_6522_1_T2C_H = $C409 ; 6522 #1 Timer2 High-order Latch/Counter
MOCK_6522_1_SR = $C40A ; 6522 #1 Shift Register
MOCK_6522_1_ACR = $C40B ; 6522 #1 Auxiliary Control Register
MOCK_6522_1_PCR = $C40C ; 6522 #1 Peripheral Control Register
MOCK_6522_1_IFR = $C40D ; 6522 #1 Interrupt Flag Register
MOCK_6522_1_IER = $C40E ; 6522 #1 Interrupt Enable Register
MOCK_6522_1_ORAN = $C40F ; 6522 #1 port a data, no handshake
; right channel
MOCK_6522_2_ORB = $C480 ; 6522 #2 port b data
MOCK_6522_2_ORA = $C481 ; 6522 #2 port a data
MOCK_6522_2_DDRB = $C482 ; 6522 #2 data direction port B
MOCK_6522_2_DDRA = $C483 ; 6522 #2 data direction port A
MOCK_6522_2_T1C_L = $C484 ; 6522 #2 Low-order counter
MOCK_6522_2_T1C_H = $C485 ; 6522 #2 High-order counter
MOCK_6522_2_T1L_L = $C486 ; 6522 #2 Low-order latch
MOCK_6522_2_T1L_H = $C487 ; 6522 #2 High-order latch
MOCK_6522_2_T2C_L = $C488 ; 6522 #2 Timer2 Low-order Latch/Counter
MOCK_6522_2_T2C_H = $C489 ; 6522 #2 Timer2 High-order Latch/Counter
MOCK_6522_2_SR = $C48A ; 6522 #2 Shift Register
MOCK_6522_2_ACR = $C48B ; 6522 #2 Auxiliary Control Register
MOCK_6522_2_PCR = $C48C ; 6522 #2 Peripheral Control Register
MOCK_6522_2_IFR = $C48D ; 6522 #2 Interrupt Flag Register
MOCK_6522_2_IER = $C48E ; 6522 #2 Interrupt Enable Register
MOCK_6522_2_ORAN = $C48F ; 6522 #2 port a data, no handshake
; 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 = $7 ; 1 1 1
;========================
; Mockingboard Init
;========================
; Initialize the 6522s
; set the data direction for all pins of PortA/PortB to be output
mockingboard_init:
lda #$ff ; all 8 pins output (1), portA
sta MOCK_6522_1_DDRA
sta MOCK_6522_2_DDRA
; only 3 pins output (1), port B
lda #$7
sta MOCK_6522_1_DDRB
sta MOCK_6522_2_DDRB
reset_ay_both:
;======================
; Reset Left AY-3-8910
;======================
reset_ay_left:
lda #MOCK_AY_RESET
sta MOCK_6522_1_ORB
lda #MOCK_AY_INACTIVE
sta MOCK_6522_1_ORB
; AY-3-8913: Wait 5 us
nop
nop
nop
nop
nop
;======================
; Reset Right AY-3-8910
;======================
reset_ay_right:
lda #MOCK_AY_RESET
sta MOCK_6522_2_ORB
lda #MOCK_AY_INACTIVE
sta MOCK_6522_2_ORB
; AY-3-8913: Wait 5 us
nop
nop
nop
nop
nop
;=========================
; Setup initial conditions
;=========================
; 7: ENABLE
ldx #7
lda #$38 ; noise disabled, ABC enabled
sta MB_VALUE
jsr write_ay_both
;=========================
; Setup Interrupt Handler
;=========================
; Vector address goes to 0x3fe/0x3ff
; FIXME: should chain any existing handler
lda #<interrupt_handler
sta $03fe
lda #>interrupt_handler
sta $03ff
;============================
; Enable 60Hz clock on 6522
;============================
sei ; disable interrupts just in case
lda #$40 ; Continuous interrupts, don't touch PB7
sta $C40B ; ACR register
lda #$7F ; clear all interrupt flags
sta $C40E ; IER register (interrupt enable)
lda #$C0
sta $C40D ; IFR: 1100, enable interrupt on timer one oflow
sta $C40E ; IER: 1100, enable timer one interrupt
lda #$1a
sta $C404 ; write into low-order latch
lda #$41
sta $C405 ; write into high-order latch,
; load both values into counter
; clear interrupt and start counting
; 9c40 / 1e6 = .040s, 25Hz
; 4fe7 / 1e6 = .020s, 50Hz
; 411a / 1e6 = .016s, 60Hz
rts
interrupt_handler:
; A saved by firmware in $45
; sta $45
txa
pha ; save X
tya
pha ; save Y
bit $C404 ; clear 6522 interrupt by reading T1C-L ; 4
jsr play_music
pla
tay ; restore Y
pla
tax ; restore X
lda $45 ; restore A
rti ; return from interrupt ; 6
;=========================================
; Write Right/Left to save value AY-3-8910
;=========================================
; register in X
; value in MB_VALUE
write_ay_both:
; address
stx MOCK_6522_1_ORA ; put address on PA1 ; 4
stx MOCK_6522_2_ORA ; put address on PA2 ; 4
lda #MOCK_AY_LATCH_ADDR ; latch_address on PB1 ; 2
sta MOCK_6522_1_ORB ; latch_address on PB1 ; 4
sta MOCK_6522_2_ORB ; latch_address on PB2 ; 4
lda #MOCK_AY_INACTIVE ; go inactive ; 2
sta MOCK_6522_1_ORB ; 4
sta MOCK_6522_2_ORB ; 4
;===========
; 28
; value
lda MB_VALUE ; 3
sta MOCK_6522_1_ORA ; put value on PA1 ; 4
sta MOCK_6522_2_ORA ; put value on PA2 ; 4
lda #MOCK_AY_WRITE ; ; 2
sta MOCK_6522_1_ORB ; write on PB1 ; 4
sta MOCK_6522_2_ORB ; write on PB2 ; 4
lda #MOCK_AY_INACTIVE ; go inactive ; 2
sta MOCK_6522_1_ORB ; 4
sta MOCK_6522_2_ORB ; 4
;===========
; 31
rts ; 6
;===========
; 65
mockingboard_mute:
ldx #7
lda #$ff
sta MB_VALUE
jmp write_ay_both