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99 lines
3.1 KiB
NASM
99 lines
3.1 KiB
NASM
// A simple SID music player using RASTER IRQ
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/// @file
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/// Commodore 64 Registers and Constants
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/// @file
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/// The MOS 6526 Complex Interface Adapter (CIA)
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///
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/// http://archive.6502.org/datasheets/mos_6526_cia_recreated.pdf
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// Commodore 64 PRG executable file
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.file [name="music_irq.prg", type="prg", segments="Program"]
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.segmentdef Program [segments="Basic, Code, Data"]
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.segmentdef Basic [start=$0801]
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.segmentdef Code [start=$80d]
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.segmentdef Data [startAfter="Code"]
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.segment Basic
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:BasicUpstart(main)
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/// Value that disables all CIA interrupts when stored to the CIA Interrupt registers
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.const CIA_INTERRUPT_CLEAR_ALL = $7f
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/// VICII IRQ Status/Enable Raster
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// @see #IRQ_ENABLE #IRQ_STATUS
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/// 0 | RST| Reaching a certain raster line. The line is specified by writing
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/// | | to register 0xd012 and bit 7 of $d011 and internally stored by
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/// | | the VIC for the raster compare. The test for reaching the
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/// | | interrupt raster line is done in cycle 0 of every line (for line
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/// | | 0, in cycle 1).
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.const IRQ_RASTER = 1
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.const OFFSET_STRUCT_MOS6526_CIA_INTERRUPT = $d
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.const OFFSET_STRUCT_MOS6569_VICII_CONTROL1 = $11
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.const OFFSET_STRUCT_MOS6569_VICII_RASTER = $12
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.const OFFSET_STRUCT_MOS6569_VICII_IRQ_ENABLE = $1a
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.const OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR = $20
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.const OFFSET_STRUCT_MOS6569_VICII_IRQ_STATUS = $19
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/// The VIC-II MOS 6567/6569
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.label VICII = $d000
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/// The CIA#1: keyboard matrix, joystick #1/#2
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.label CIA1 = $dc00
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/// The vector used when the KERNAL serves IRQ interrupts
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.label KERNEL_IRQ = $314
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// Pointer to the music init routine
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.label musicInit = MUSIC
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// Pointer to the music play routine
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.label musicPlay = MUSIC+3
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.segment Code
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// Raster IRQ Routine playing music
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irq_play: {
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// (VICII->BORDER_COLOR)++;
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inc VICII+OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR
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// (*musicPlay)()
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// Play SID
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jsr musicPlay
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// VICII->IRQ_STATUS = IRQ_RASTER
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// Acknowledge the IRQ
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lda #IRQ_RASTER
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_IRQ_STATUS
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// (VICII->BORDER_COLOR)--;
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dec VICII+OFFSET_STRUCT_MOS6569_VICII_BORDER_COLOR
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// }
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jmp $ea31
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}
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// Setup Raster IRQ and initialize SID player
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main: {
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// asm
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sei
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// (*musicInit)()
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jsr musicInit
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// CIA1->INTERRUPT = CIA_INTERRUPT_CLEAR_ALL
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// Disable CIA 1 Timer IRQ
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lda #CIA_INTERRUPT_CLEAR_ALL
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sta CIA1+OFFSET_STRUCT_MOS6526_CIA_INTERRUPT
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// VICII->CONTROL1 &=$7f
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// Set raster line to $fd
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lda #$7f
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and VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_CONTROL1
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// VICII->RASTER = $fd
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lda #$fd
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_RASTER
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// VICII->IRQ_ENABLE = IRQ_RASTER
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// Enable Raster Interrupt
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lda #IRQ_RASTER
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sta VICII+OFFSET_STRUCT_MOS6569_VICII_IRQ_ENABLE
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// *KERNEL_IRQ = &irq_play
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// Set the IRQ routine
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lda #<irq_play
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sta KERNEL_IRQ
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lda #>irq_play
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sta KERNEL_IRQ+1
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// asm
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cli
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// }
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rts
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}
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.segment Data
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.pc = $1000 "MUSIC"
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// SID tune at an absolute address
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MUSIC:
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.const music = LoadSid("toiletrensdyr.sid")
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.fill music.size, music.getData(i)
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