diff options
Diffstat (limited to 'gme/Sap_Cpu.h')
-rw-r--r-- | gme/Sap_Cpu.h | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/gme/Sap_Cpu.h b/gme/Sap_Cpu.h new file mode 100644 index 00000000..712f63cd --- /dev/null +++ b/gme/Sap_Cpu.h @@ -0,0 +1,83 @@ +// Atari 6502 CPU emulator + +// Game_Music_Emu 0.5.2 +#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 = LONG_MAX / 2 + 1 }; + +class Sap_Cpu { +public: + typedef BOOST::uint8_t uint8_t; + + // 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 { + BOOST::uint16_t pc; + BOOST::uint8_t a; + BOOST::uint8_t x; + BOOST::uint8_t y; + BOOST::uint8_t status; + BOOST::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 |