dos33fsprogs/games/duke/pt3_lib_mockingboard_setup.s

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2020-11-15 04:18:51 +00:00
; 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 = $7 ; 1 1 1
;========================
; Mockingboard Init
;========================
; Initialize the 6522s
; set the data direction for all pins of PortA/PortB to be output
mockingboard_init:
lda #$ff ; all output (1)
mock_init_smc1:
sta MOCK_6522_DDRB1
sta MOCK_6522_DDRA1
mock_init_smc2:
sta MOCK_6522_DDRB2
sta MOCK_6522_DDRA2
rts
;===================================
;===================================
; Reset Both AY-3-8910s
;===================================
;===================================
;======================
; Reset Left AY-3-8910
;======================
reset_ay_both:
lda #MOCK_AY_RESET
reset_ay_smc1:
sta MOCK_6522_ORB1
lda #MOCK_AY_INACTIVE
reset_ay_smc2:
sta MOCK_6522_ORB1
;======================
; Reset Right AY-3-8910
;======================
;reset_ay_right:
;could be merged with both
lda #MOCK_AY_RESET
reset_ay_smc3:
sta MOCK_6522_ORB2
lda #MOCK_AY_INACTIVE
reset_ay_smc4:
sta MOCK_6522_ORB2
rts
; Write sequence
; Inactive -> Latch Address -> Inactive -> Write Data -> Inactive
;=========================================
; Write Right/Left to save value AY-3-8910
;=========================================
; register in X
; value in MB_VALUE
; note the datasheet says 10,000ns (10 cycle) max hold
; time on the write signals. So interleaving write/left
; write might violate that
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write_ay_both:
; address
; write left
lda #MOCK_AY_LATCH_ADDR ; latch_address on PB1 ; 2
ldy #MOCK_AY_INACTIVE ; go inactive ; 2
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write_ay_smc1:
stx MOCK_6522_ORA1 ; put address on PA1 ; 4
write_ay_smc2:
sta MOCK_6522_ORB1 ; latch_address on PB1 ; 4
write_ay_smc3:
sty MOCK_6522_ORB1 ; go inactive ; 4
; write right
stx MOCK_6522_ORA2 ; put address on PA2 ; 4
sta MOCK_6522_ORB2 ; latch_address on PB2 ; 4
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sty MOCK_6522_ORB2 ; 4
;===========
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; value
lda MB_VALUE ; 3
; write left
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write_ay_smc4:
sta MOCK_6522_ORA1 ; put value on PA1 ; 4
lda #MOCK_AY_WRITE ; ; 2
write_ay_smc5:
sta MOCK_6522_ORB1 ; write on PB1 ; 4
write_ay_smc6:
sty MOCK_6522_ORB1 ; 4
lda MB_VALUE ; 3
; write right
sta MOCK_6522_ORA2 ; put value on PA2 ; 4
lda #MOCK_AY_WRITE ; ; 2
sta MOCK_6522_ORB2 ; write on PB2 ; 4
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sty MOCK_6522_ORB2 ; 4
;===========
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rts ; 6
;===========
; 63
write_ay_both_end:
;.assert >write_ay_both = >write_ay_both_end, error, "write_ay_both crosses page"
;=======================================
; clear ay -- clear all 14 AY registers
; should silence the card
;=======================================
; 7+(74*14)+5=1048
clear_ay_both:
ldx #13 ; 2
lda #0 ; 2
sta MB_VALUE ; 3
clear_ay_left_loop:
jsr write_ay_both ; 6+63
dex ; 2
bpl clear_ay_left_loop ; 3
; -1
rts ; 6
clear_ay_end:
;.assert >clear_ay_both = >clear_ay_end, error, "clear_ay_both crosses page"
;=============================
; Setup
;=============================
mockingboard_setup_interrupt:
;===========================
; Check for Apple IIc
;===========================
; it does interrupts differently
lda $FBB3 ; IIe and newer is $06
cmp #6
beq apple_iie_or_newer
jmp done_apple_detect
apple_iie_or_newer:
lda $FBC0 ; 0 on a IIc
bne done_apple_detect
apple_iic:
; activate IIc mockingboard?
; this might only be necessary to allow detection
; I get the impression the Mockingboard 4c activates
; when you access any of the 6522 ports in Slot 4
lda #$ff
; don't bother patching these, IIc mockingboard always slot 4?
sta MOCK_6522_DDRA1
sta MOCK_6522_T1CL
; bypass the firmware interrupt handler
; should we do this on IIe too? probably faster
sei ; disable interrupts
lda $c08b ; disable ROM (enable language card)
lda $c08b
lda #<interrupt_handler
sta $fffe
lda #>interrupt_handler
sta $ffff
lda #$EA ; nop out the "lda $45" in the irq hand
sta interrupt_smc
sta interrupt_smc+1
done_apple_detect:
;=========================
; 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 50Hz clock on 6522
;============================
; 4fe7 / 1e6 = .020s, 50Hz
; 9c40 / 1e6 = .040s, 25Hz
; 411a / 1e6 = .016s, 60Hz
sei ; disable interrupts just in case
lda #$40 ; Continuous interrupts, don't touch PB7
setup_irq_smc1:
sta MOCK_6522_ACR ; ACR register
lda #$7F ; clear all interrupt flags
setup_irq_smc2:
sta MOCK_6522_IER ; IER register (interrupt enable)
lda #$C0
setup_irq_smc3:
sta MOCK_6522_IFR ; IFR: 1100, enable interrupt on timer one oflow
setup_irq_smc4:
sta MOCK_6522_IER ; IER: 1100, enable timer one interrupt
lda #$E7
setup_irq_smc5:
sta MOCK_6522_T1CL ; write into low-order latch
lda #$4f
setup_irq_smc6:
sta MOCK_6522_T1CH ; write into high-order latch,
; load both values into counter
; clear interrupt and start counting
rts