dos33fsprogs/monkey/ym_play.s
2020-09-17 01:12:40 -04:00

88 lines
1.9 KiB
ArmAsm

mockingboard_detect:
;================================
; Mockingboard detect
;================================
jsr mockingboard_detect_slot4 ; call detection routine
stx MB_DETECTED
;================================
; Mockingboard start
;================================
mockingboard_setup:
sei ; disable interrupts just in case
jsr mockingboard_init
jsr reset_ay_both
jsr clear_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 50Hz clock on 6522
;============================
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 $C40E ; IER: 1100, enable timer one interrupt
lda #$e7
sta $C404 ; write into low-order latch
lda #$4f
sta $C405 ; write into high-order latch,
; load both values into counter
; clear interrupt and start counting
; 4fe7 / 1e6 = .020s, 50Hz
; 9c40 / 1e6 = .040s, 25Hz
;============================
; Start Playing
;============================
main_loop:
lda MB_DETECTED
beq mockingboard_setup_done
lda #0
sta DONE_PLAYING
sta WHICH_CHUNK
sta MB_CHUNK_OFFSET
sta MB_ADDRL ; we are aligned, so should be 0
lda #>music_start
sta MB_ADDRH
;=====================================
; clear register area
;=====================================
ldx #13 ; 2
lda #0 ; 2
mb_setup_clear_reg:
sta REGISTER_DUMP,X ; clear register value ; 4
sta REGISTER_OLD,X ; clear old values ; 4
dex ; 2
bpl mb_setup_clear_reg ; 2nt/3
cli ; start interrupts
mockingboard_setup_done:
rts