92 lines
2.3 KiB
C++
92 lines
2.3 KiB
C++
// Nintendo Game Boy CPU emulator
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// Treats every instruction as taking 4 cycles
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// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
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#ifndef GB_CPU_H
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#define GB_CPU_H
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#include "blargg_common.h"
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#include "blargg_endian.h"
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typedef unsigned gb_addr_t; // 16-bit CPU address
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class Gb_Cpu {
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enum { clocks_per_instr = 4 };
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public:
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// Clear registers and map all pages to unmapped
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void reset( void* unmapped = 0 );
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// Map code memory (memory accessed via the program counter). Start and size
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// must be multiple of page_size.
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enum { page_size = 0x2000 };
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void map_code( gb_addr_t start, unsigned size, void* code );
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uint8_t* get_code( gb_addr_t );
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// Push a byte on the stack
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void push_byte( int );
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// Game Boy Z80 registers. *Not* kept updated during a call to run().
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struct core_regs_t {
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#if BLARGG_BIG_ENDIAN
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uint8_t b, c, d, e, h, l, flags, a;
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#else
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uint8_t c, b, e, d, l, h, a, flags;
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#endif
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};
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struct registers_t : core_regs_t {
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long pc; // more than 16 bits to allow overflow detection
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uint16_t sp;
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};
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registers_t r;
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// Interrupt enable flag set by EI and cleared by DI
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//bool interrupts_enabled; // unused
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// Base address for RST vectors (normally 0)
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gb_addr_t rst_base;
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// If CPU executes opcode 0xFF at this address, it treats as illegal instruction
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enum { idle_addr = 0xF00D };
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// Run CPU for at least 'count' cycles and return false, or return true if
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// illegal instruction is encountered.
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bool run( blargg_long count );
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// Number of clock cycles remaining for most recent run() call
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blargg_long remain() const { return state->remain * clocks_per_instr; }
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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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public:
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Gb_Cpu() : rst_base( 0 ) { state = &state_; }
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enum { page_shift = 13 };
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enum { page_count = 0x10000 >> page_shift };
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private:
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// noncopyable
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Gb_Cpu( const Gb_Cpu& );
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Gb_Cpu& operator = ( const Gb_Cpu& );
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struct state_t {
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uint8_t* code_map [page_count + 1];
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blargg_long remain;
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};
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state_t* state; // points to state_ or a local copy within run()
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state_t state_;
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void set_code_page( int, uint8_t* );
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};
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inline uint8_t* Gb_Cpu::get_code( gb_addr_t addr )
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{
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return state->code_map [addr >> page_shift] + addr
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#if !BLARGG_NONPORTABLE
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% (unsigned) page_size
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#endif
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;
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}
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#endif
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