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82 lines
2 KiB
C
82 lines
2 KiB
C
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// Atari 6502 CPU emulator
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// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
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#ifndef SAP_CPU_H
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#define SAP_CPU_H
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#include "blargg_common.h"
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typedef blargg_long sap_time_t; // clock cycle count
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typedef unsigned sap_addr_t; // 16-bit address
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enum { future_sap_time = INT_MAX / 2 + 1 };
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class Sap_Cpu {
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public:
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// Clear all registers and keep pointer to 64K memory passed in
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void reset( void* mem_64k );
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// Run until specified time is reached. Returns true if suspicious/unsupported
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// instruction was encountered at any point during run.
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bool run( sap_time_t end_time );
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// Registers are not updated until run() returns (except I flag in status)
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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 status;
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uint8_t sp;
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};
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registers_t r;
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enum { idle_addr = 0xFEFF };
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// Time of beginning of next instruction to be executed
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sap_time_t time() const { return state->time + state->base; }
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void set_time( sap_time_t t ) { state->time = t - state->base; }
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void adjust_time( int delta ) { state->time += delta; }
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sap_time_t irq_time() const { return irq_time_; }
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void set_irq_time( sap_time_t );
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sap_time_t end_time() const { return end_time_; }
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void set_end_time( sap_time_t );
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public:
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Sap_Cpu() { state = &state_; }
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enum { irq_inhibit = 0x04 };
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private:
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struct state_t {
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sap_time_t base;
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sap_time_t time;
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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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sap_time_t irq_time_;
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sap_time_t end_time_;
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uint8_t* mem;
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inline sap_time_t update_end_time( sap_time_t end, sap_time_t irq );
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};
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inline sap_time_t Sap_Cpu::update_end_time( sap_time_t t, sap_time_t irq )
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{
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if ( irq < t && !(r.status & irq_inhibit) ) t = irq;
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sap_time_t delta = state->base - t;
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state->base = t;
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return delta;
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}
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inline void Sap_Cpu::set_irq_time( sap_time_t t )
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{
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state->time += update_end_time( end_time_, (irq_time_ = t) );
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}
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inline void Sap_Cpu::set_end_time( sap_time_t t )
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{
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state->time += update_end_time( (end_time_ = t), irq_time_ );
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}
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#endif
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