mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-12-29 00:31:52 +00:00
88 lines
1.9 KiB
ArmAsm
88 lines
1.9 KiB
ArmAsm
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mockingboard_detect:
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;================================
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; Mockingboard detect
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;================================
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jsr mockingboard_detect_slot4 ; call detection routine
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stx MB_DETECTED
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;================================
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; Mockingboard start
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;================================
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mockingboard_setup:
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sei ; disable interrupts just in case
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jsr mockingboard_init
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jsr reset_ay_both
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jsr clear_ay_both
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;=========================
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; Setup Interrupt Handler
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;=========================
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; Vector address goes to 0x3fe/0x3ff
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; FIXME: should chain any existing handler
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lda #<interrupt_handler
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sta $03fe
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lda #>interrupt_handler
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sta $03ff
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;============================
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; Enable 50Hz clock on 6522
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;============================
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lda #$40 ; Continuous interrupts, don't touch PB7
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sta $C40B ; ACR register
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lda #$7F ; clear all interrupt flags
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sta $C40E ; IER register (interrupt enable)
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lda #$C0
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sta $C40D ; IFR: 1100, enable interrupt on timer one oflow
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sta $C40E ; IER: 1100, enable timer one interrupt
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lda #$e7
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sta $C404 ; write into low-order latch
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lda #$4f
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sta $C405 ; write into high-order latch,
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; load both values into counter
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; clear interrupt and start counting
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; 4fe7 / 1e6 = .020s, 50Hz
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; 9c40 / 1e6 = .040s, 25Hz
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;============================
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; Start Playing
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;============================
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main_loop:
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lda MB_DETECTED
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beq mockingboard_setup_done
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lda #0
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sta DONE_PLAYING
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sta WHICH_CHUNK
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sta MB_CHUNK_OFFSET
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sta MB_ADDR_L ; we are aligned, so should be 0
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lda #>music_start
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sta MB_ADDR_H
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;=====================================
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; clear register area
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;=====================================
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ldx #13 ; 2
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lda #0 ; 2
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mb_setup_clear_reg:
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sta REGISTER_DUMP,X ; clear register value ; 4
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sta REGISTER_OLD,X ; clear old values ; 4
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dex ; 2
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bpl mb_setup_clear_reg ; 2nt/3
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cli ; start interrupts
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mockingboard_setup_done:
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rts
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