Genesis-Plus-GX/source/m68k/m68kcpu.c

/* ======================================================================== */
/* ========================= LICENSING & COPYRIGHT ======================== */
/* ======================================================================== */

#if 0
static const char copyright_notice[] =
"MUSASHI\n"
"Version 3.32 (2007-12-15)\n"
"A portable Motorola M680x0 processor emulation engine.\n"
"Copyright Karl Stenerud.  All rights reserved.\n"
"\n"
"This code may be freely used for non-commercial purpooses as long as this\n"
"copyright notice remains unaltered in the source code and any binary files\n"
"containing this code in compiled form.\n"
"\n"
"All other licensing terms must be negotiated with the author\n"
"(Karl Stenerud).\n"
"\n"
"The latest version of this code can be obtained at:\n"
"http://kstenerud.cjb.net\n"
;
#endif


/* ======================================================================== */
/* ================================= NOTES ================================ */
/* ======================================================================== */
 
 /* Modified by Eke-Eke for Genesis Plus GX:

    - removed unused stuff to reduce memory usage / optimize execution (multiple CPU types support, NMI support, ...)
    - moved stuff to compile statically in a single object file
    - implemented support for global cycle count (shared by 68k & Z80 CPU)
    - added support for interrupt latency (Sesame's Street Counting Cafe, Fatal Rewind)
    - added proper cycle use on reset
    - added cycle accurate timings for MUL/DIV instructions (thanks to Jorge Cwik !) 
    - fixed undocumented flags for DIV instructions (Blood Shot)
    
  */

/* ======================================================================== */
/* ================================ INCLUDES ============================== */
/* ======================================================================== */

#include "m68kcpu.h"
#include "m68kops.h"

/* ======================================================================== */
/* ================================= DATA ================================= */
/* ======================================================================== */

static int irq_latency;

/* ======================================================================== */
/* =============================== CALLBACKS ============================== */
/* ======================================================================== */

/* Default callbacks used if the callback hasn't been set yet, or if the
 * callback is set to NULL
 */

#if M68K_EMULATE_INT_ACK == OPT_ON
/* Interrupt acknowledge */
static int default_int_ack_callback(int int_level)
{
  CPU_INT_LEVEL = 0;
  return M68K_INT_ACK_AUTOVECTOR;
}
#endif

#if M68K_EMULATE_RESET == OPT_ON
/* Called when a reset instruction is executed */
static void default_reset_instr_callback(void)
{
}
#endif

#if M68K_TAS_HAS_CALLBACK == OPT_ON
/* Called when a tas instruction is executed */
static int default_tas_instr_callback(void)
{
  return 1; // allow writeback
}
#endif

#if M68K_EMULATE_FC == OPT_ON
/* Called every time there's bus activity (read/write to/from memory */
static void default_set_fc_callback(unsigned int new_fc)
{
}
#endif


/* ======================================================================== */
/* ================================= API ================================== */
/* ======================================================================== */

/* Access the internals of the CPU */
unsigned int m68k_get_reg(m68k_register_t regnum)
{
  switch(regnum)
  {
    case M68K_REG_D0:  return m68ki_cpu.dar[0];
    case M68K_REG_D1:  return m68ki_cpu.dar[1];
    case M68K_REG_D2:  return m68ki_cpu.dar[2];
    case M68K_REG_D3:  return m68ki_cpu.dar[3];
    case M68K_REG_D4:  return m68ki_cpu.dar[4];
    case M68K_REG_D5:  return m68ki_cpu.dar[5];
    case M68K_REG_D6:  return m68ki_cpu.dar[6];
    case M68K_REG_D7:  return m68ki_cpu.dar[7];
    case M68K_REG_A0:  return m68ki_cpu.dar[8];
    case M68K_REG_A1:  return m68ki_cpu.dar[9];
    case M68K_REG_A2:  return m68ki_cpu.dar[10];
    case M68K_REG_A3:  return m68ki_cpu.dar[11];
    case M68K_REG_A4:  return m68ki_cpu.dar[12];
    case M68K_REG_A5:  return m68ki_cpu.dar[13];
    case M68K_REG_A6:  return m68ki_cpu.dar[14];
    case M68K_REG_A7:  return m68ki_cpu.dar[15];
    case M68K_REG_PC:  return MASK_OUT_ABOVE_32(m68ki_cpu.pc);
    case M68K_REG_SR:  return  m68ki_cpu.t1_flag        |
                  (m68ki_cpu.s_flag << 11)              |
                   m68ki_cpu.int_mask                   |
                  ((m68ki_cpu.x_flag & XFLAG_SET) >> 4) |
                  ((m68ki_cpu.n_flag & NFLAG_SET) >> 4) |
                  ((!m68ki_cpu.not_z_flag) << 2)        |
                  ((m68ki_cpu.v_flag & VFLAG_SET) >> 6) |
                  ((m68ki_cpu.c_flag & CFLAG_SET) >> 8);
    case M68K_REG_SP:  return m68ki_cpu.dar[15];
    case M68K_REG_USP:  return m68ki_cpu.s_flag ? m68ki_cpu.sp[0] : m68ki_cpu.dar[15];
    case M68K_REG_ISP:  return m68ki_cpu.s_flag ? m68ki_cpu.dar[15] : m68ki_cpu.sp[4];
#if M68K_EMULATE_PREFETCH
    case M68K_REG_PREF_ADDR:  return m68ki_cpu.pref_addr;
    case M68K_REG_PREF_DATA:  return m68ki_cpu.pref_data;
#endif
    case M68K_REG_IR:  return m68ki_cpu.ir;
    default:      return 0;
  }
}

void m68k_set_reg(m68k_register_t regnum, unsigned int value)
{
  switch(regnum)
  {
    case M68K_REG_D0:  REG_D[0] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D1:  REG_D[1] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D2:  REG_D[2] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D3:  REG_D[3] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D4:  REG_D[4] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D5:  REG_D[5] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D6:  REG_D[6] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_D7:  REG_D[7] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A0:  REG_A[0] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A1:  REG_A[1] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A2:  REG_A[2] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A3:  REG_A[3] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A4:  REG_A[4] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A5:  REG_A[5] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A6:  REG_A[6] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_A7:  REG_A[7] = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_PC:  m68ki_jump(MASK_OUT_ABOVE_32(value)); return;
    case M68K_REG_SR:  m68ki_set_sr(value); return;
    case M68K_REG_SP:  REG_SP = MASK_OUT_ABOVE_32(value); return;
    case M68K_REG_USP:  if(FLAG_S)
                REG_USP = MASK_OUT_ABOVE_32(value);
              else
                REG_SP = MASK_OUT_ABOVE_32(value);
              return;
    case M68K_REG_ISP:  if(FLAG_S)
                REG_SP = MASK_OUT_ABOVE_32(value);
              else
                REG_ISP = MASK_OUT_ABOVE_32(value);
              return;
    case M68K_REG_IR:  REG_IR = MASK_OUT_ABOVE_16(value); return;
#if M68K_EMULATE_PREFETCH
    case M68K_REG_PREF_ADDR:  CPU_PREF_ADDR = MASK_OUT_ABOVE_32(value); return;
#endif
    default:      return;
  }
}

/* Set the callbacks */
#if M68K_EMULATE_INT_ACK == OPT_ON
void m68k_set_int_ack_callback(int  (*callback)(int int_level))
{
  CALLBACK_INT_ACK = callback ? callback : default_int_ack_callback;
}
#endif

#if M68K_EMULATE_RESET == OPT_ON
void m68k_set_reset_instr_callback(void  (*callback)(void))
{
  CALLBACK_RESET_INSTR = callback ? callback : default_reset_instr_callback;
}
#endif

#if M68K_TAS_HAS_CALLBACK == OPT_ON
void m68k_set_tas_instr_callback(int  (*callback)(void))
{
  CALLBACK_TAS_INSTR = callback ? callback : default_tas_instr_callback;
}
#endif

#if M68K_EMULATE_FC == OPT_ON
void m68k_set_fc_callback(void  (*callback)(unsigned int new_fc))
{
  CALLBACK_SET_FC = callback ? callback : default_set_fc_callback;
}
#endif

#ifdef LOGVDP
extern void error(char *format, ...);
extern uint16 v_counter;
#endif

/* ASG: rewrote so that the int_level is a mask of the IPL0/IPL1/IPL2 bits */
/* KS: Modified so that IPL* bits match with mask positions in the SR
 *     and cleaned out remenants of the interrupt controller.
 */
void m68k_update_irq(unsigned int mask)
{
  /* Update IRQ level */
  CPU_INT_LEVEL |= (mask << 8);
  
#ifdef LOGVDP
  error("[%d(%d)][%d(%d)] IRQ Level = %d(0x%02x) (%x)\n", v_counter, mcycles_68k/3420, mcycles_68k, mcycles_68k%3420,CPU_INT_LEVEL>>8,FLAG_INT_MASK,m68k_get_reg(M68K_REG_PC));
#endif

  /* Check interrupt mask to process IRQ  */
  m68ki_check_interrupts();
}

void m68k_set_irq(unsigned int int_level)
{
  /* Set IRQ level */
  CPU_INT_LEVEL = int_level << 8;
  
#ifdef LOGVDP
  error("[%d(%d)][%d(%d)] IRQ Level = %d(0x%02x) (%x)\n", v_counter, mcycles_68k/3420, mcycles_68k, mcycles_68k%3420,CPU_INT_LEVEL>>8,FLAG_INT_MASK,m68k_get_reg(M68K_REG_PC));
#endif

  /* Check interrupt mask to process IRQ  */
  m68ki_check_interrupts();
}

/* IRQ latency (Fatal Rewind, Sesame's Street Counting Cafe)*/
void m68k_set_irq_delay(unsigned int int_level)
{
  /* Prevent reentrance */
  if (!irq_latency)
  {
    /* This is always triggered from MOVE instructions (VDP CTRL port write) */
    /* We just make sure this is not a MOVE.L instruction as we could be in */
    /* the middle of its execution (first memory write).                   */
    if ((REG_IR & 0xF000) != 0x2000)
    {
      /* Finish executing current instruction */
      USE_CYCLES(CYC_INSTRUCTION[REG_IR]);

      /* One instruction delay before interrupt */
      irq_latency = 1;
      m68ki_trace_t1() /* auto-disable (see m68kcpu.h) */
      m68ki_use_data_space() /* auto-disable (see m68kcpu.h) */
      REG_IR = m68ki_read_imm_16();
      m68ki_instruction_jump_table[REG_IR]();
      m68ki_exception_if_trace() /* auto-disable (see m68kcpu.h) */
      irq_latency = 0;
    }

    /* Set IRQ level */
    CPU_INT_LEVEL = int_level << 8;
  }
  
#ifdef LOGVDP
  error("[%d(%d)][%d(%d)] IRQ Level = %d(0x%02x) (%x)\n", v_counter, mcycles_68k/3420, mcycles_68k, mcycles_68k%3420,CPU_INT_LEVEL>>8,FLAG_INT_MASK,m68k_get_reg(M68K_REG_PC));
#endif

  /* Check interrupt mask to process IRQ  */
  m68ki_check_interrupts(); /* Level triggered (IRQ) */
}


void m68k_run(unsigned int cycles) 
{
  /* Make sure we're not stopped */
  if (CPU_STOPPED)
  {
    mcycles_68k = cycles;
    return;
  }

  /* Return point for when we have an address error (TODO: use goto) */
  m68ki_set_address_error_trap() /* auto-disable (see m68kcpu.h) */

  /* Save end cycles count for when CPU is stopped */
  end_cycles = cycles;
  
  while (mcycles_68k < cycles)
  {
    /* Set tracing accodring to T1. */
    m68ki_trace_t1() /* auto-disable (see m68kcpu.h) */

    /* Set the address space for reads */
    m68ki_use_data_space() /* auto-disable (see m68kcpu.h) */

    /* Decode next instruction */
    REG_IR = m68ki_read_imm_16();
	
    /* Execute instruction */
	  m68ki_instruction_jump_table[REG_IR](); /* TODO: use labels table with goto */
    USE_CYCLES(CYC_INSTRUCTION[REG_IR]); /* TODO: move into instruction handlers */

    /* Trace m68k_exception, if necessary */
    m68ki_exception_if_trace(); /* auto-disable (see m68kcpu.h) */
  }
}

void m68k_init(void)
{
  static uint emulation_initialized = 0;

  /* The first call to this function initializes the opcode handler jump table */
  if(!emulation_initialized)
  {
    m68ki_build_opcode_table();
    emulation_initialized = 1;
  }

#if M68K_EMULATE_INT_ACK == OPT_ON
  m68k_set_int_ack_callback(NULL);
#endif
#if M68K_EMULATE_RESET == OPT_ON
  m68k_set_reset_instr_callback(NULL);
#endif
#if M68K_TAS_HAS_CALLBACK == OPT_ON
  m68k_set_tas_instr_callback(NULL);
#endif
#if M68K_EMULATE_FC == OPT_ON
  m68k_set_fc_callback(NULL);
#endif
}

/* Pulse the RESET line on the CPU */
void m68k_pulse_reset(void)
{
  /* Clear all stop levels and eat up all remaining cycles */
  CPU_STOPPED = 0;
#if M68K_EMULATE_ADDRESS_ERROR
  CPU_RUN_MODE = RUN_MODE_BERR_AERR_RESET;
#endif

  /* Turn off tracing */
  FLAG_T1 = 0;
  m68ki_clear_trace()

  /* Interrupt mask to level 7 */
  FLAG_INT_MASK = 0x0700;
  CPU_INT_LEVEL = 0;
  irq_latency = 0;

  /* Go to supervisor mode */
  m68ki_set_s_flag(SFLAG_SET);

  /* Invalidate the prefetch queue */
#if M68K_EMULATE_PREFETCH
  /* Set to arbitrary number since our first fetch is from 0 */
  CPU_PREF_ADDR = 0x1000;
#endif /* M68K_EMULATE_PREFETCH */

  /* Read the initial stack pointer and program counter */
  m68ki_jump(0);
  REG_SP = m68ki_read_imm_32();
  REG_PC = m68ki_read_imm_32();
  m68ki_jump(REG_PC);

#if M68K_EMULATE_ADDRESS_ERROR
  CPU_RUN_MODE = RUN_MODE_NORMAL;
#endif

  USE_CYCLES(CYC_EXCEPTION[EXCEPTION_RESET]);
}

/* Pulse the HALT line on the CPU */
void m68k_pulse_halt(void)
{
  CPU_STOPPED |= STOP_LEVEL_HALT;
}


/* ======================================================================== */
/* ============================== END OF FILE ============================= */
/* ======================================================================== */