chip-8/src/vcpu.h

#pragma once

#define VCPU_FREQ 600
#define DTST_FREQ 60
#define SCREEN_FREQ 60
#define REG_FLAG 0xF

typedef struct VCPU_State {
  // Program Counter (16 bits but only 12 bits used (4096 memory addresses))
  unsigned short PC;

  // Index register (16 bits but only 12 bits used (4096 memory addresses))
  unsigned short I;

  // Stack register (16 bits)
  unsigned short S;
  unsigned short stack[100]; // Emulated stack

  // General purpose registers (8 bits each)
  // Note last one often used as a flag register
  unsigned char V[16];

  // Delay timer (8 bits)
  unsigned char DT;

  // Sound timer (8 bits)
  unsigned char ST;

  // Intruction (opcode + decoded fields)
  unsigned short opcode;
  unsigned char X;
  unsigned char Y;
  unsigned char N;
  unsigned char NN;
  unsigned short NNN;

  // Keypressed
  int keypressed; // Not 0 if a key was pressed
  unsigned char key;
  
  // Count VCPU ticks
  int dt_ticks;
  int st_ticks;
  int screen_ticks;
} VCPU_State;

void VCPUInit();
void VCPUFetch();
void VCPUDecode();
void VCPUExecute();
void VCPUTick();
void VCPUDoubleDabble(unsigned char x, unsigned char *u, unsigned char *t, unsigned char *h);
void VCPUDump();