4cade/src/hw.mockingboard.a

;license:MIT
;(c) 2019-2020 by Andrew Roughan, qkumba, 4am
;
; Mockingboard support functions
;

;------------------------------------------------------------------------------
; GetMockingboardStuff
; detect Mockingboard card by searching for 6522 timers across all slots 7->1
; access 6522 timers with deterministic cycle counts
;
;   based on prior art in Mockingboard Developers Toolkit
;   with optimisation from deater/french touch
;   also takes into account FastChip //e clock difference
;
; in:    A/Y contains address of callback to call if card was found
;          (this will be called before the speech detection routine, and
;          (zp$81 will contain the slot in form $Cx)
;        /!\ ALL ACCELERATORS MUST BE OFF OR SET TO 1 MHZ
; out:   if card was found, X = #$?n where n is the slot number of the card, otherwise #$00
;                           and    bit 6 = 0 if Mockingboard Sound I found
;                               or bit 6 = 1 if Mockingboard Sound II or "A" found
;                           and    bit 7 = 1 if Mockingboard Sound/Speech I or "C" found
;        flags clobbered
;        zp $80-$82 clobbered
;        A/Y clobbered
;------------------------------------------------------------------------------
GetMockingboardStuff
         +STAY @callback+1
         lda   #$00
         sta   $80
         sta   $82                   ; type
         ldx   #$C1
@slotLoop
         stx   $81
         ldy   #$04                  ; 6522 #1 $Cx04
         jsr   @timercheck
         beq   @foundI

@nextSlot
         inx
         cpx   #$C8
         bne   @slotLoop
         ldx   #$00                  ; not found
         rts

@foundI  ; sound I or better
         jsr   @callback
         ldy   #$84                  ; 6522 #2 $Cx84
         jsr   @timercheck
         beq   @foundII

         ldy   #$0c
         sty   @mb_smc3 + 1
         iny
         sty   @mb_smc8 + 1
         iny
         sty   @mb_smc7 + 1
         sty   @mb_smc11 + 1

         +HIDE_NEXT_2_BYTES
@foundII  ;stereo
         ror   $82

         lda   $81
         sta   @mb_smc1 + 2
         sta   @mb_smc2 + 2
         sta   @mb_smc3 + 2
         sta   @mb_smc4 + 2
         sta   @mb_smc5 + 2
         sta   @mb_smc6 + 2
         sta   @mb_smc7 + 2
         sta   @mb_smc8 + 2
         sta   @mb_smc9 + 2
         sta   @mb_smc10 + 2
         sta   @mb_smc11 + 2
         sta   @mb_smc12 + 2
         sta   @mb_smc13 + 2

         ; detect speech chip

         sei
         lda   #<@mb_irq
         sta   $3fe
         sta   $fffe
         lda   #>@mb_irq
         sta   $3ff
         sta   $ffff

         lda   #0
@mb_smc1
         sta   $c403
@mb_smc2
         sta   $c402
         lda   #$0c
@mb_smc3
         sta   $c48c
         lda   #$80
@mb_smc4
         sta   $c443
         lda   #$c0
@mb_smc5
         sta   $c440
         lda   #$70
@mb_smc6
         sta   $c443
         lda   #$82
@mb_smc7
         sta   $c48e

         ldx   #0
         ldy   #0
         sec
         cli

@wait_irq
         lda   $80
         bne   @got_irq
         iny
         bne   @wait_irq
         inx
         bne   @wait_irq
         clc

@got_irq
         sei
         ror   $82

@onlyI
         lda   $81
         and   #7
         ora   $82
         tax
         lda   #<Ignore
         sta   $fffe
         lda   #>Ignore
         sta   $ffff
         rts                         ; found

@timercheck
         sec
         lda   ($80),y               ; read 6522 timer low byte
         sbc   ($80),y               ; second time 
         cmp   #5                    ; looking for (-)8 cycles between reads
         beq   +
         cmp   #6                    ; FastChip //e clock is different
+        rts

@mb_irq
         lda   #2
@mb_smc8
         sta   $c48d
         lda   #0
@mb_smc9
         sta   $c440
         lda   #$70
@mb_smc10
         sta   $c443
         sta   $80
         lda   #2
@mb_smc11
         sta   $c48e
         lda   #$ff
@mb_smc12
         sta   $c403
         lda   #7
@mb_smc13
         sta   $c402
         lda   $45
         rti

@callback
         jmp   $FDFD                 ; SMC