apps/codecs/libgme/hes_cpu.h

   1 // PC Engine CPU emulator for use with HES music files
   2
   3 // Game_Music_Emu 0.5.2
   4 #ifndef HES_CPU_H
   5 #define HES_CPU_H
   6
   7 #include "blargg_common.h"
   8
   9 typedef blargg_long hes_time_t; // clock cycle count
  10 typedef unsigned hes_addr_t; // 16-bit address
  11
  12 struct Hes_Emu;
  13
  14 enum { future_hes_time = LONG_MAX / 2 + 1 };
  15 enum { page_size = 0x2000 };
  16 enum { page_shift = 13 };
  17 enum { page_count = 8 };
  18
  19 // Attempt to execute instruction here results in CPU advancing time to
  20 // lesser of irq_time() and end_time() (or end_time() if IRQs are
  21 // disabled)
  22 enum { idle_addr = 0x1FFF };
  23
  24 // Can read this many bytes past end of a page
  25 enum { cpu_padding = 8 };
  26 enum { irq_inhibit = 0x04 };
  27
  28
  29 // Cpu state
  30 struct state_t {
  31         uint8_t const* code_map [page_count + 1];
  32         hes_time_t base;
  33         blargg_long time;
  34 };
  35
  36 // Cpu registers
  37 struct registers_t {
  38         uint16_t pc;
  39         uint8_t a;
  40         uint8_t x;
  41         uint8_t y;
  42         uint8_t status;
  43         uint8_t sp;
  44 };
  45
  46 struct Hes_Cpu {
  47         struct registers_t r;
  48
  49         hes_time_t irq_time;
  50         hes_time_t end_time;
  51
  52         struct state_t* state; // points to state_ or a local copy within run()
  53         struct state_t state_;
  54
  55         // page mapping registers
  56         uint8_t mmr [page_count + 1];
  57         uint8_t ram [page_size];
  58 };
  59
  60 // Init cpu state
  61 void Cpu_init( struct Hes_Cpu* this );
  62
  63 // Reset hes cpu
  64 void Cpu_reset( struct Hes_Cpu* this );
  65
  66 // Set end_time and run CPU from current time. Returns true if any illegal
  67 // instructions were encountered.
  68 bool Cpu_run( struct Hes_Emu* this, hes_time_t end_time ) ICODE_ATTR;
  69
  70 void Cpu_set_mmr( struct Hes_Emu* this, int reg, int bank ) ICODE_ATTR;
  71
  72 // Time of ning of next instruction to be executed
  73 static inline hes_time_t Cpu_time( struct Hes_Cpu* this )
  74 {
  75         return this->state->time + this->state->base;
  76 }
  77
  78 static inline uint8_t const* Cpu_get_code( struct Hes_Cpu* this, hes_addr_t addr )
  79 {
  80         return this->state->code_map [addr >> page_shift] + addr
  81         #if !defined (BLARGG_NONPORTABLE)
  82                 % (unsigned) page_size
  83         #endif
  84         ;
  85 }
  86
  87 static inline int Cpu_update_end_time( struct Hes_Cpu* this, uint8_t reg_status, hes_time_t t, hes_time_t irq )
  88 {
  89         if ( irq < t && !(reg_status & irq_inhibit) ) t = irq;
  90         int delta = this->state->base - t;
  91         this->state->base = t;
  92         return delta;
  93 }
  94
  95 #endif