138 lines
2.7 KiB
ArmAsm
138 lines
2.7 KiB
ArmAsm
; This code detects a SSI263 chip on a Mockingboard
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; it does this by trying to enable the chip and waiting for
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; the SSI-263 to signal an interrupt when done.
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; If the interrupt never comes then assume no SSI-263 is present
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; The code assumes the SSI-263 is hooked to VIA6522 #2 (?)
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;=============================
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;=============================
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; detect SSI263
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;=============================
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;=============================
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; A = slot of mockingboard
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detect_ssi263:
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sta ssi263_slot ; store for later
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and #$7
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ora #$c0 ; turn slot number into address
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sta ssid_wc_smc1+2 ; update the read/write routines
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sei ; disable IRQ
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lda $3fe ; backup the IRQ handler
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sta irq1backup
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lda $3ff
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sta irq2backup
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lda #<mb_irq ; point IRQ handler to our code
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sta $3fe
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lda #>mb_irq
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sta $3ff
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; Set 6522#2 peripheral control register to recognize the signal
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; from the speech chip.
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lda #(VIA6522_PCR2_CA2_LOW|VIA6522_PCR2_CA1_NEG)
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ldx #VIA6522_PCR2
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jsr ssi263_d_write_chip
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; Raise control bit in register 3 of SSI-263
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lda #SSI263_CAA_CTL
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ldx #SSI263_CAA
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jsr ssi263_d_write_chip
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; Transitioned inflection (when CTL is toggled)
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lda #SSI263_DRP_TRANSITIONED_INFLECTION
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ldx #SSI263_DRP
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jsr ssi263_d_write_chip
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; Lower control bit in SSI-263
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lda #$70 ; CTL=0, T=6, AMP=0
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ldx #SSI263_CAA
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jsr ssi263_d_write_chip
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; Enable 6522 interrupt on input CA2
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lda #(VIA6522_IER2_SET|VIA6522_IER2_CA1)
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ldx #VIA6522_IER2
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jsr ssi263_d_write_chip
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ldx #0 ; clear counts
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ldy #0
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cli ; enable interrupts
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wait_irq:
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lda irq_count ; see if irq happened
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bne got_irq
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iny ; otherwise increase counts
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bne wait_irq
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inx ;
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bne wait_irq
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got_irq:
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sei ; disable interrupts
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rts
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;========================
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; detection IRQ handler
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;========================
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mb_irq:
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txa ; save X
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pha
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; Clear the 6522 interrupt flag
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lda #VIA6522_IFR2_CA1
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ldx #VIA6522_IFR2
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jsr ssi263_d_write_chip
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; disable speech
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; Raise control bit in register 3 of SSI-263
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lda #SSI263_CAA_CTL
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ldx #SSI263_CAA
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jsr ssi263_d_write_chip
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; Disable talking on SSI-263 (when CTL is toggled)
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lda #SSI263_DRP_DISABLE_AR
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ldx #SSI263_DRP
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jsr ssi263_d_write_chip
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; Lower control bit in SSI-263
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lda #$70 ; also T=7?
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ldx #SSI263_CAA
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jsr ssi263_d_write_chip
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; increment our irq count
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inc irq_count
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; Disable 6522 interrupts
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lda #VIA6522_IER2_CA1
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ldx #VIA6522_IER2
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jsr ssi263_d_write_chip
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pla ; restore X
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tax
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lda $45 ; restore accumulator
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rti ; return from interrupt
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;========================
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; write_chip
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;========================
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ssi263_d_write_chip:
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ssid_wc_smc1:
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sta $C000,X
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rts
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irq_count: .byte $00
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irq1backup: .byte $00
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irq2backup: .byte $00
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ssi263_slot: .byte $00
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