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718112a8fe
Currently none of these is being used, but eventually they will, once more code gets ported over. So it's better to have them right away and avoid editing the project file too much, only to revert that later.
91 lines
2.3 KiB
C++
91 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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