c97c5e5d17
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30490 a1c6a512-1295-4272-9138-f99709370657
109 lines
3 KiB
C
109 lines
3 KiB
C
// NES cpu emulator
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// Game_Music_Emu 0.6-pre
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#ifndef NES_CPU_H
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#define NES_CPU_H
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#include "blargg_common.h"
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#include "blargg_source.h"
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typedef int nes_time_t;
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typedef int addr_t;
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enum { page_bits = 11 };
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enum { page_size = 1 << page_bits };
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enum { page_count = 0x10000 >> page_bits };
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// Unmapped page should be filled with this
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enum { halt_opcode = 0x22 };
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enum { future_time = INT_MAX/2 + 1 };
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enum { irq_inhibit_mask = 0x04 };
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// Can read this many bytes past end of a page
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enum { cpu_padding = 8 };
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struct registers_t {
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uint16_t pc;
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uint8_t a;
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uint8_t x;
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uint8_t y;
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uint8_t flags;
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uint8_t sp;
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};
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struct cpu_state_t {
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uint8_t const* code_map [page_count + 1];
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nes_time_t base;
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int time;
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};
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struct Nes_Cpu {
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// NES 6502 registers. NOT kept updated during emulation.
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struct registers_t r;
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nes_time_t irq_time;
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nes_time_t end_time;
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struct cpu_state_t* cpu_state; // points to cpu_state_ or a local copy
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struct cpu_state_t cpu_state_;
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};
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static inline void Cpu_init( struct Nes_Cpu* this )
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{
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this->cpu_state = &this->cpu_state_;
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}
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// Clears registers and maps all pages to unmapped_page
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void Cpu_reset( struct Nes_Cpu* this, void const* unmapped_page );
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// Maps code memory (memory accessed via the program counter). Start and size
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// must be multiple of page_size. If mirror_size is non-zero, the first
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// mirror_size bytes are repeated over the range. mirror_size must be a
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// multiple of page_size.
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void Cpu_map_code( struct Nes_Cpu* this, addr_t start, int size, void const* code, int mirror_size );
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// Time of beginning of next instruction to be executed
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static inline nes_time_t Cpu_time( struct Nes_Cpu* this ) { return this->cpu_state->time + this->cpu_state->base; }
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static inline void Cpu_set_time( struct Nes_Cpu* this, nes_time_t t ) { this->cpu_state->time = t - this->cpu_state->base; }
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static inline void Cpu_adjust_time( struct Nes_Cpu* this, int delta ) { this->cpu_state->time += delta; }
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// Clocks past end (negative if before)
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static inline int Cpu_time_past_end( struct Nes_Cpu* this ) { return this->cpu_state->time; }
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#define NES_CPU_PAGE( addr ) ((unsigned) (addr) >> page_bits)
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#ifdef BLARGG_NONPORTABLE
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#define NES_CPU_OFFSET( addr ) (addr)
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#else
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#define NES_CPU_OFFSET( addr ) ((addr) & (page_size - 1))
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#endif
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// Accesses emulated memory as cpu does
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static inline uint8_t const* Cpu_get_code( struct Nes_Cpu* this, addr_t addr )
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{
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return this->cpu_state_.code_map [NES_CPU_PAGE( addr )] + NES_CPU_OFFSET( addr );
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}
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static inline void Cpu_update_end_time( struct Nes_Cpu* this, nes_time_t end, nes_time_t irq )
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{
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if ( end > irq && !(this->r.flags & irq_inhibit_mask) )
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end = irq;
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this->cpu_state->time += this->cpu_state->base - end;
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this->cpu_state->base = end;
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}
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// Time of next IRQ
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static inline void Cpu_set_irq_time( struct Nes_Cpu* this, nes_time_t t )
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{
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this->irq_time = t;
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Cpu_update_end_time( this, this->end_time, t );
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}
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static inline void Cpu_set_end_time( struct Nes_Cpu* this, nes_time_t t )
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{
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this->end_time = t;
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Cpu_update_end_time( this, t, this->irq_time );
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}
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#endif
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