dos33fsprogs/demos/wargames/ssi263_detect.s
2021-09-19 00:01:26 -04:00

140 lines
2.7 KiB
ArmAsm

; This code detects a SSI263 chip on a Mockingboard
; it does this by trying to enable the chip and waiting for
; the SSI-263 to signal an interrupt when done.
; If the interrupt never comes then assume no SSI-263 is present
; The code assumes the SSI-263 is hooked to VIA6522 #2 (?)
;=============================
;=============================
; detect SSI263
;=============================
;=============================
; A = slot of mockingboard
; carry set if found
detect_ssi263:
and #$7
ora #$c0 ; turn slot number into address
sta ssid_wc_smc1+2 ; update the read/write routines
sei ; disable IRQ
lda $3fe ; backup the IRQ handler
sta irq1backup
lda $3ff
sta irq2backup
lda #<mb_irq ; point IRQ handler to our code
sta $3fe
lda #>mb_irq
sta $3ff
; Set 6522#2 peripheral control register to recognize the signal
; from the speech chip.
lda #(VIA6522_PCR2_CA2_LOW|VIA6522_PCR2_CA1_NEG)
ldx #VIA6522_PCR2
jsr ssi263_d_write_chip
; Raise control bit in register 3 of SSI-263
lda #SSI263_CAA_CTL
ldx #SSI263_CAA
jsr ssi263_d_write_chip
; Transitioned inflection (when CTL is toggled)
lda #SSI263_DRP_TRANSITIONED_INFLECTION
ldx #SSI263_DRP
jsr ssi263_d_write_chip
; Lower control bit in SSI-263
lda #$70 ; CTL=0, T=6, AMP=0
ldx #SSI263_CAA
jsr ssi263_d_write_chip
; Enable 6522 interrupt on input CA2
lda #(VIA6522_IER2_SET|VIA6522_IER2_CA1)
ldx #VIA6522_IER2
jsr ssi263_d_write_chip
ldx #0 ; clear counts
ldy #0
cli ; enable interrupts
wait_irq:
lda irq_count ; see if irq happened
bne got_irq
iny ; otherwise increase counts
bne wait_irq
inx ;
bne wait_irq
sei
clc ; not found
rts
got_irq:
sei ; disable interrupts
sec ; found
rts
;========================
; detection IRQ handler
;========================
mb_irq:
txa ; save X
pha
; Clear the 6522 interrupt flag
lda #VIA6522_IFR2_CA1
ldx #VIA6522_IFR2
jsr ssi263_d_write_chip
; disable speech
; Raise control bit in register 3 of SSI-263
lda #SSI263_CAA_CTL
ldx #SSI263_CAA
jsr ssi263_d_write_chip
; Disable talking on SSI-263 (when CTL is toggled)
lda #SSI263_DRP_DISABLE_AR
ldx #SSI263_DRP
jsr ssi263_d_write_chip
; Lower control bit in SSI-263
lda #$70 ; also T=7?
ldx #SSI263_CAA
jsr ssi263_d_write_chip
; increment our irq count
inc irq_count
; Disable 6522 interrupts
lda #VIA6522_IER2_CA1
ldx #VIA6522_IER2
jsr ssi263_d_write_chip
pla ; restore X
tax
lda $45 ; restore accumulator
rti ; return from interrupt
;========================
; write_chip
;========================
ssi263_d_write_chip:
ssid_wc_smc1:
sta $C000,X
rts
irq_count: .byte $00
irq1backup: .byte $00
irq2backup: .byte $00