1 // NES 2A03 APU sound chip emulator
7 #include "blargg_common.h"
10 enum { apu_status_addr
= 0x4015 };
11 enum { apu_osc_count
= 5 };
12 enum { apu_no_irq
= INT_MAX
/ 2 + 1 };
13 enum { apu_irq_waiting
= 0 };
15 enum { apu_io_addr
= 0x4000 };
16 enum { apu_io_size
= 0x18 };
21 nes_time_t last_dmc_time
;
24 struct Nes_Osc
* oscs
[apu_osc_count
];
25 struct Nes_Square square1
;
26 struct Nes_Square square2
;
27 struct Nes_Noise noise
;
28 struct Nes_Triangle triangle
;
32 nes_time_t last_time
; // has been run until this time in current frame
33 nes_time_t earliest_irq_
;
36 int frame_delay
; // cycles until frame counter runs next
37 int frame
; // current frame (0-3)
41 void (*irq_notifier_
)( void* user_data
);
44 Synth square_synth
; // shared by squares
48 void Apu_init( struct Nes_Apu
* this );
50 // Set buffer to generate all sound into, or disable sound if NULL
51 void Apu_output( struct Nes_Apu
* this, struct Blip_Buffer
* ) ICODE_ATTR
;
53 // All time values are the number of cpu clock cycles relative to the
54 // beginning of the current time frame. Before resetting the cpu clock
55 // count, call end_frame( last_cpu_time ).
57 // Write to register (0x4000-0x4017, except 0x4014 and 0x4016)
58 void Apu_write_register( struct Nes_Apu
* this, nes_time_t
, addr_t
, int data
) ICODE_ATTR
;
60 // Read from status register at 0x4015
61 int Apu_read_status( struct Nes_Apu
* this, nes_time_t
) ICODE_ATTR
;
63 // Run all oscillators up to specified time, end current time frame, then
64 // start a new time frame at time 0. Time frames have no effect on emulation
65 // and each can be whatever length is convenient.
66 void Apu_end_frame( struct Nes_Apu
* this, nes_time_t
) ICODE_ATTR
;
68 // Additional optional features (can be ignored without any problem)
70 // Reset internal frame counter, registers, and all oscillators.
71 // Use PAL timing if pal_timing is true, otherwise use NTSC timing.
72 // Set the DMC oscillator's initial DAC value to initial_dmc_dac without
74 void Apu_reset( struct Nes_Apu
* this, bool pal_mode
, int initial_dmc_dac
);
76 // Adjust frame period
77 void Apu_set_tempo( struct Nes_Apu
* this, double );
79 // Set overall volume (default is 1.0)
80 void Apu_volume( struct Nes_Apu
* this, double );
82 // Run DMC until specified time, so that any DMC memory reads can be
83 // accounted for (i.e. inserting cpu wait states).
84 void Apu_run_until( struct Nes_Apu
* this, nes_time_t
) ICODE_ATTR
;
86 // Set sound output of specific oscillator to buffer. If buffer is NULL,
87 // the specified oscillator is muted and emulation accuracy is reduced.
88 // The oscillators are indexed as follows: 0) Square 1, 1) Square 2,
89 // 2) Triangle, 3) Noise, 4) DMC.
90 static inline void Apu_osc_output( struct Nes_Apu
* this, int osc
, struct Blip_Buffer
* buf
)
92 assert( (unsigned) osc
< apu_osc_count
);
93 this->oscs
[osc
]->output
= buf
;
96 // Set memory reader callback used by DMC oscillator to fetch samples.
97 // When callback is invoked, 'user_data' is passed unchanged as the
99 static inline void Apu_dmc_reader( struct Nes_Apu
* this, int (*func
)( void*, addr_t
), void* user_data
)
101 this->dmc
.prg_reader_data
= user_data
;
102 this->dmc
.prg_reader
= func
;
105 // Set IRQ time callback that is invoked when the time of earliest IRQ
106 // may have changed, or NULL to disable. When callback is invoked,
107 // 'user_data' is passed unchanged as the first parameter.
108 static inline void Apu_irq_notifier( struct Nes_Apu
* this, void (*func
)( void* user_data
), void* user_data
)
110 this->irq_notifier_
= func
;
111 this->irq_data
= user_data
;
114 // Count number of DMC reads that would occur if 'run_until( t )' were executed.
115 // If last_read is not NULL, set *last_read to the earliest time that
116 // 'count_dmc_reads( time )' would result in the same result.
117 static inline int Apu_count_dmc_reads( struct Nes_Apu
* this, nes_time_t time
, nes_time_t
* last_read
)
119 return Dmc_count_reads( &this->dmc
, time
, last_read
);
122 static inline nes_time_t
Dmc_next_read_time( struct Nes_Dmc
* this )
124 if ( this->osc
.length_counter
== 0 )
125 return apu_no_irq
; // not reading
127 return this->apu
->last_dmc_time
+ this->osc
.delay
+ (long) (this->bits_remain
- 1) * this->period
;
130 // Time when next DMC memory read will occur
131 static inline nes_time_t
Apu_next_dmc_read_time( struct Nes_Apu
* this ) { return Dmc_next_read_time( &this->dmc
); }
132 void Apu_irq_changed( struct Nes_Apu
* this ) ICODE_ATTR
;