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Sap_Cpu.h
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Sap_Cpu.h
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// Atari 6502 CPU emulator
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
#ifndef SAP_CPU_H
#define SAP_CPU_H
#include "blargg_common.h"
typedef blargg_long sap_time_t; // clock cycle count
typedef unsigned sap_addr_t; // 16-bit address
enum { future_sap_time = INT_MAX / 2 + 1 };
class Sap_Cpu {
public:
// Clear all registers and keep pointer to 64K memory passed in
void reset( void* mem_64k );
// Run until specified time is reached. Returns true if suspicious/unsupported
// instruction was encountered at any point during run.
bool run( sap_time_t end_time );
// Registers are not updated until run() returns (except I flag in status)
struct registers_t {
uint16_t pc;
uint8_t a;
uint8_t x;
uint8_t y;
uint8_t status;
uint8_t sp;
};
registers_t r;
enum { idle_addr = 0xFEFF };
// Time of beginning of next instruction to be executed
sap_time_t time() const { return state->time + state->base; }
void set_time( sap_time_t t ) { state->time = t - state->base; }
void adjust_time( int delta ) { state->time += delta; }
sap_time_t irq_time() const { return irq_time_; }
void set_irq_time( sap_time_t );
sap_time_t end_time() const { return end_time_; }
void set_end_time( sap_time_t );
public:
Sap_Cpu() { state = &state_; }
enum { irq_inhibit = 0x04 };
private:
struct state_t {
sap_time_t base;
sap_time_t time;
};
state_t* state; // points to state_ or a local copy within run()
state_t state_;
sap_time_t irq_time_;
sap_time_t end_time_;
uint8_t* mem;
inline sap_time_t update_end_time( sap_time_t end, sap_time_t irq );
};
inline sap_time_t Sap_Cpu::update_end_time( sap_time_t t, sap_time_t irq )
{
if ( irq < t && !(r.status & irq_inhibit) ) t = irq;
sap_time_t delta = state->base - t;
state->base = t;
return delta;
}
inline void Sap_Cpu::set_irq_time( sap_time_t t )
{
state->time += update_end_time( end_time_, (irq_time_ = t) );
}
inline void Sap_Cpu::set_end_time( sap_time_t t )
{
state->time += update_end_time( (end_time_ = t), irq_time_ );
}
#endif

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