path: root/sim/m68hc11/m68hc11_sim.c

/* m6811_cpu.c -- 68HC11&68HC12 CPU Emulation
   Copyright 1999-2022 Free Software Foundation, Inc.
   Written by Stephane Carrez (stcarrez@nerim.fr)

This file is part of GDB, GAS, and the GNU binutils.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* This must come before any other includes.  */
#include "defs.h"

#include "sim-main.h"
#include "sim-assert.h"
#include "sim-module.h"
#include "sim-options.h"
#include "sim-signal.h"

#include <stdlib.h>

enum {
  OPTION_CPU_RESET = OPTION_START,
  OPTION_EMUL_OS,
  OPTION_CPU_CONFIG,
  OPTION_CPU_BOOTSTRAP,
  OPTION_CPU_MODE
};

static DECLARE_OPTION_HANDLER (cpu_option_handler);

static const OPTION cpu_options[] =
{
  { {"cpu-reset", no_argument, NULL, OPTION_CPU_RESET },
      '\0', NULL, "Reset the CPU",
      cpu_option_handler },

  { {"emulos",    no_argument, NULL, OPTION_EMUL_OS },
      '\0', NULL, "Emulate some OS system calls (read, write, ...)",
      cpu_option_handler },

  { {"cpu-config", required_argument, NULL, OPTION_CPU_CONFIG },
      '\0', NULL, "Specify the initial CPU configuration register",
      cpu_option_handler },

  { {"bootstrap", no_argument, NULL, OPTION_CPU_BOOTSTRAP },
      '\0', NULL, "Start the processing in bootstrap mode",
      cpu_option_handler },

  { {NULL, no_argument, NULL, 0}, '\0', NULL, NULL, NULL }
};


static SIM_RC
cpu_option_handler (SIM_DESC sd, sim_cpu *cpu,
                    int opt, char *arg, int is_command)
{
  int val;
  
  cpu = STATE_CPU (sd, 0);
  switch (opt)
    {
    case OPTION_CPU_RESET:
      sim_board_reset (sd);
      break;

    case OPTION_EMUL_OS:
      cpu->cpu_emul_syscall = 1;
      break;

    case OPTION_CPU_CONFIG:
      if (sscanf(arg, "0x%x", &val) == 1
          || sscanf(arg, "%d", &val) == 1)
        {
          cpu->cpu_config = val;
          cpu->cpu_use_local_config = 1;
        }
      else
        cpu->cpu_use_local_config = 0;
      break;

    case OPTION_CPU_BOOTSTRAP:
       cpu->cpu_start_mode = "bootstrap";
       break;

    case OPTION_CPU_MODE:
      break;
    }

  return SIM_RC_OK;
}

    
void
cpu_call (sim_cpu *cpu, uint16_t addr)
{

  cpu_set_pc (cpu, addr);
}

void
cpu_return (sim_cpu *cpu)
{
}

/* Set the stack pointer and re-compute the current frame.  */
void
cpu_set_sp (sim_cpu *cpu, uint16_t val)
{
  cpu->cpu_regs.sp = val;
}

static uint16_t
cpu_get_reg (sim_cpu *cpu, uint8_t reg)
{
  switch (reg)
    {
    case 0:
      return cpu_get_x (cpu);

    case 1:
      return cpu_get_y (cpu);

    case 2:
      return cpu_get_sp (cpu);

    case 3:
      return cpu_get_pc (cpu);

    default:
      return 0;
    }
}

static uint16_t
cpu_get_src_reg (sim_cpu *cpu, uint8_t reg)
{
  switch (reg)
    {
    case 0:
      return cpu_get_a (cpu);

    case 1:
      return cpu_get_b (cpu);

    case 2:
      return cpu_get_ccr (cpu);

    case 3:
      return cpu_get_tmp3 (cpu);

    case 4:
      return cpu_get_d (cpu);

    case 5:
      return cpu_get_x (cpu);

    case 6:
      return cpu_get_y (cpu);

    case 7:
      return cpu_get_sp (cpu);

    default:
      return 0;
    }
}

static void
cpu_set_dst_reg (sim_cpu *cpu, uint8_t reg, uint16_t val)
{
  switch (reg)
    {
    case 0:
      cpu_set_a (cpu, val);
      break;

    case 1:
      cpu_set_b (cpu, val);
      break;

    case 2:
      cpu_set_ccr (cpu, val);
      break;

    case 3:
      cpu_set_tmp2 (cpu, val);
      break;

    case 4:
      cpu_set_d (cpu, val);
      break;

    case 5:
      cpu_set_x (cpu, val);
      break;

    case 6:
      cpu_set_y (cpu, val);
      break;

    case 7:
      cpu_set_sp (cpu, val);
      break;

    default:
      break;
    }
}

static void
cpu_set_reg (sim_cpu *cpu, uint8_t reg, uint16_t val)
{
  switch (reg)
    {
    case 0:
      cpu_set_x (cpu, val);
      break;
      
    case 1:
      cpu_set_y (cpu, val);
      break;
      
    case 2:
      cpu_set_sp (cpu, val);
      break;
      
    case 3:
      cpu_set_pc (cpu, val);
      break;
      
    default:
      break;
    }
}

/* Returns the address of a 68HC12 indexed operand.
   Pre and post modifications are handled on the source register.  */
uint16_t
cpu_get_indexed_operand_addr (sim_cpu *cpu, int restricted)
{
  uint8_t reg;
  uint16_t sval;
  uint16_t addr;
  uint8_t code;

  code = cpu_fetch8 (cpu);

  /* n,r with 5-bit signed constant.  */
  if ((code & 0x20) == 0)
    {
      reg = (code >> 6) & 3;
      sval = (code & 0x1f);
      if (code & 0x10)
	sval |= 0xfff0;

      addr = cpu_get_reg (cpu, reg);
      addr += sval;
    }

  /* Auto pre/post increment/decrement.  */
  else if ((code & 0xc0) != 0xc0)
    {
      reg = (code >> 6) & 3;
      sval = (code & 0x0f);
      if (sval & 0x8)
	{
	  sval |= 0xfff0;
	}
      else
	{
	  sval = sval + 1;
	}
      addr = cpu_get_reg (cpu, reg);
      cpu_set_reg (cpu, reg, addr + sval);
      if ((code & 0x10) == 0)
	{
	  addr += sval;
	}
    }

  /* [n,r] 16-bits offset indexed indirect.  */
  else if ((code & 0x07) == 3)
    {
      if (restricted)
	{
	  return 0;
	}
      reg = (code >> 3) & 0x03;
      addr = cpu_get_reg (cpu, reg);
      addr += cpu_fetch16 (cpu);
      addr = memory_read16 (cpu, addr);
      cpu_add_cycles (cpu, 1);
    }
  else if ((code & 0x4) == 0)
    {
      if (restricted)
	{
	  return 0;
	}
      reg = (code >> 3) & 0x03;
      addr = cpu_get_reg (cpu, reg);
      if (code & 0x2)
	{
	  sval = cpu_fetch16 (cpu);
	  cpu_add_cycles (cpu, 1);
	}
      else
	{
	  sval = cpu_fetch8 (cpu);
	  if (code & 0x1)
	    sval |= 0xff00;
	  cpu_add_cycles (cpu, 1);
	}
      addr += sval;
    }
  else
    {
      reg = (code >> 3) & 0x03;
      addr = cpu_get_reg (cpu, reg);
      switch (code & 3)
	{
	case 0:
	  addr += cpu_get_a (cpu);
	  break;
	case 1:
	  addr += cpu_get_b (cpu);
	  break;
	case 2:
	  addr += cpu_get_d (cpu);
	  break;
	case 3:
	default:
	  addr += cpu_get_d (cpu);
	  addr = memory_read16 (cpu, addr);
	  cpu_add_cycles (cpu, 1);
	  break;
	}
    }

  return addr;
}

static uint8_t
cpu_get_indexed_operand8 (sim_cpu *cpu, int restricted)
{
  uint16_t addr;

  addr = cpu_get_indexed_operand_addr (cpu, restricted);
  return memory_read8 (cpu, addr);
}

static uint16_t
cpu_get_indexed_operand16 (sim_cpu *cpu, int restricted)
{
  uint16_t addr;

  addr = cpu_get_indexed_operand_addr (cpu, restricted);
  return memory_read16 (cpu, addr);
}

void
cpu_move8 (sim_cpu *cpu, uint8_t code)
{
  uint8_t src;
  uint16_t addr;

  switch (code)
    {
    case 0x0b:
      src = cpu_fetch8 (cpu);
      addr = cpu_fetch16 (cpu);
      break;

    case 0x08:
      addr = cpu_get_indexed_operand_addr (cpu, 1);
      src = cpu_fetch8 (cpu);
      break;

    case 0x0c:
      addr = cpu_fetch16 (cpu);
      src = memory_read8 (cpu, addr);
      addr = cpu_fetch16 (cpu);
      break;

    case 0x09:
      addr = cpu_get_indexed_operand_addr (cpu, 1);
      src = memory_read8 (cpu, cpu_fetch16 (cpu));
      break;

    case 0x0d:
      src = cpu_get_indexed_operand8 (cpu, 1);
      addr = cpu_fetch16 (cpu);
      break;

    case 0x0a:
      src = cpu_get_indexed_operand8 (cpu, 1);
      addr = cpu_get_indexed_operand_addr (cpu, 1);
      break;

    default:
      sim_engine_abort (CPU_STATE (cpu), cpu, 0,
			"Invalid code 0x%0x -- internal error?", code);
      return;
    }
  memory_write8 (cpu, addr, src);
}

void
cpu_move16 (sim_cpu *cpu, uint8_t code)
{
  uint16_t src;
  uint16_t addr;

  switch (code)
    {
    case 0x03:
      src = cpu_fetch16 (cpu);
      addr = cpu_fetch16 (cpu);
      break;

    case 0x00:
      addr = cpu_get_indexed_operand_addr (cpu, 1);
      src = cpu_fetch16 (cpu);
      break;

    case 0x04:
      addr = cpu_fetch16 (cpu);
      src = memory_read16 (cpu, addr);
      addr = cpu_fetch16 (cpu);
      break;

    case 0x01:
      addr = cpu_get_indexed_operand_addr (cpu, 1);
      src = memory_read16 (cpu, cpu_fetch16 (cpu));
      break;

    case 0x05:
      src = cpu_get_indexed_operand16 (cpu, 1);
      addr = cpu_fetch16 (cpu);
      break;

    case 0x02:
      src = cpu_get_indexed_operand16 (cpu, 1);
      addr = cpu_get_indexed_operand_addr (cpu, 1);
      break;

    default:
      sim_engine_abort (CPU_STATE (cpu), cpu, 0,
			"Invalid code 0x%0x -- internal error?", code);
      return;
    }
  memory_write16 (cpu, addr, src);
}

int
cpu_initialize (SIM_DESC sd, sim_cpu *cpu)
{
  sim_add_option_table (sd, 0, cpu_options);

  memset (&cpu->cpu_regs, 0, sizeof(cpu->cpu_regs));

  cpu->cpu_absolute_cycle = 0;
  cpu->cpu_current_cycle  = 0;
  cpu->cpu_emul_syscall   = 1;
  cpu->cpu_running        = 1;
  cpu->cpu_stop_on_interrupt = 0;
  cpu->cpu_frequency = 8 * 1000 * 1000;
  cpu->cpu_use_elf_start = 0;
  cpu->cpu_elf_start     = 0;
  cpu->cpu_use_local_config = 0;
  cpu->bank_start = 0;
  cpu->bank_end   = 0;
  cpu->bank_shift = 0;
  cpu->cpu_config        = M6811_NOSEC | M6811_NOCOP | M6811_ROMON |
    M6811_EEON;
  interrupts_initialize (sd, cpu);

  cpu->cpu_is_initialized = 1;
  return 0;
}


/* Reinitialize the processor after a reset.  */
int
cpu_reset (sim_cpu *cpu)
{
  /* Initialize the config register.
     It is only initialized at reset time.  */
  memset (cpu->ios, 0, sizeof (cpu->ios));
  if (cpu->cpu_configured_arch->arch == bfd_arch_m68hc11)
    cpu->ios[M6811_INIT] = 0x1;
  else
    cpu->ios[M6811_INIT] = 0;

  /* Output compare registers set to 0xFFFF.  */
  cpu->ios[M6811_TOC1_H] = 0xFF;
  cpu->ios[M6811_TOC1_L] = 0xFF;
  cpu->ios[M6811_TOC2_H] = 0xFF;
  cpu->ios[M6811_TOC2_L] = 0xFF;
  cpu->ios[M6811_TOC3_H] = 0xFF;
  cpu->ios[M6811_TOC4_L] = 0xFF;
  cpu->ios[M6811_TOC5_H] = 0xFF;
  cpu->ios[M6811_TOC5_L] = 0xFF;

  /* Setup the processor registers.  */
  memset (&cpu->cpu_regs, 0, sizeof(cpu->cpu_regs));
  cpu->cpu_absolute_cycle = 0;
  cpu->cpu_current_cycle  = 0;
  cpu->cpu_is_initialized = 0;

  /* Reset interrupts.  */
  interrupts_reset (&cpu->cpu_interrupts);

  /* Reinitialize the CPU operating mode.  */
  cpu->ios[M6811_HPRIO] = cpu->cpu_mode;
  return 0;
}

/* Reinitialize the processor after a reset.  */
int
cpu_restart (sim_cpu *cpu)
{
  uint16_t addr;

  /* Get CPU starting address depending on the CPU mode.  */
  if (cpu->cpu_use_elf_start == 0)
    {
      switch ((cpu->ios[M6811_HPRIO]) & (M6811_SMOD | M6811_MDA))
        {
          /* Single Chip  */
        default:
        case 0 :
          addr = memory_read16 (cpu, 0xFFFE);
          break;

          /* Expanded Multiplexed  */
        case M6811_MDA:
          addr = memory_read16 (cpu, 0xFFFE);
          break;

          /* Special Bootstrap  */
        case M6811_SMOD:
          addr = 0;
          break;

          /* Factory Test  */
        case M6811_MDA | M6811_SMOD:
          addr = memory_read16 (cpu, 0xFFFE);
          break;
        }
    }
  else
    {
      addr = cpu->cpu_elf_start;
    }
  
  /* Setup the processor registers.  */
  cpu->cpu_insn_pc  = addr;
  cpu->cpu_regs.pc  = addr;
  cpu->cpu_regs.ccr = M6811_X_BIT | M6811_I_BIT | M6811_S_BIT;
  cpu->cpu_absolute_cycle = 0;
  cpu->cpu_is_initialized = 1;
  cpu->cpu_current_cycle  = 0;

  cpu_call (cpu, addr);
  
  return 0;
}

void
print_io_reg_desc (SIM_DESC sd, io_reg_desc *desc, int val, int mode)
{
  while (desc->mask)
    {
      if (val & desc->mask)
	sim_io_printf (sd, "%s",
		       mode == 0 ? desc->short_name : desc->long_name);
      desc++;
    }
}

void
print_io_byte (SIM_DESC sd, const char *name, io_reg_desc *desc,
	       uint8_t val, uint16_t addr)
{
  sim_io_printf (sd, "  %-9.9s @ 0x%04x 0x%02x ", name, addr, val);
  if (desc)
    print_io_reg_desc (sd, desc, val, 0);
}

void
print_io_word (SIM_DESC sd, const char *name, io_reg_desc *desc,
	       uint16_t val, uint16_t addr)
{
  sim_io_printf (sd, "  %-9.9s @ 0x%04x 0x%04x ", name, addr, val);
  if (desc)
    print_io_reg_desc (sd, desc, val, 0);
}

void
cpu_ccr_update_tst8 (sim_cpu *cpu, uint8_t val)
{
  cpu_set_ccr_V (cpu, 0);
  cpu_set_ccr_N (cpu, val & 0x80 ? 1 : 0);
  cpu_set_ccr_Z (cpu, val == 0 ? 1 : 0);
}


uint16_t
cpu_fetch_relbranch (sim_cpu *cpu)
{
  uint16_t addr = (uint16_t) cpu_fetch8 (cpu);

  if (addr & 0x0080)
    {
      addr |= 0xFF00;
    }
  addr += cpu->cpu_regs.pc;
  return addr;
}

uint16_t
cpu_fetch_relbranch16 (sim_cpu *cpu)
{
  uint16_t addr = cpu_fetch16 (cpu);

  addr += cpu->cpu_regs.pc;
  return addr;
}

/* Push all the CPU registers (when an interruption occurs).  */
void
cpu_push_all (sim_cpu *cpu)
{
  if (cpu->cpu_configured_arch->arch == bfd_arch_m68hc11)
    {
      cpu_m68hc11_push_uint16 (cpu, cpu->cpu_regs.pc);
      cpu_m68hc11_push_uint16 (cpu, cpu->cpu_regs.iy);
      cpu_m68hc11_push_uint16 (cpu, cpu->cpu_regs.ix);
      cpu_m68hc11_push_uint16 (cpu, cpu->cpu_regs.d);
      cpu_m68hc11_push_uint8 (cpu, cpu->cpu_regs.ccr);
    }
  else
    {
      cpu_m68hc12_push_uint16 (cpu, cpu->cpu_regs.pc);
      cpu_m68hc12_push_uint16 (cpu, cpu->cpu_regs.iy);
      cpu_m68hc12_push_uint16 (cpu, cpu->cpu_regs.ix);
      cpu_m68hc12_push_uint16 (cpu, cpu->cpu_regs.d);
      cpu_m68hc12_push_uint8 (cpu, cpu->cpu_regs.ccr);
    }
}

/* Simulation of the dbcc/ibcc/tbcc 68HC12 conditional branch operations.  */
void
cpu_dbcc (sim_cpu *cpu)
{
  uint8_t code;
  uint16_t addr;
  uint16_t inc;
  uint16_t reg;
  
  code = cpu_fetch8 (cpu);
  switch (code & 0xc0)
    {
    case 0x80: /* ibcc */
      inc = 1;
      break;
    case 0x40: /* tbcc */
      inc = 0;
      break;
    case 0:    /* dbcc */
      inc = -1;
      break;
    default:
      abort ();
      break;
    }

  addr = cpu_fetch8 (cpu);
  if (code & 0x10)
    addr |= 0xff00;

  addr += cpu_get_pc (cpu);
  reg = cpu_get_src_reg (cpu, code & 0x07);
  reg += inc;

  /* Branch according to register value.  */
  if ((reg != 0 && (code & 0x20)) || (reg == 0 && !(code & 0x20)))
    {
      cpu_set_pc (cpu, addr);
    }
  cpu_set_dst_reg (cpu, code & 0x07, reg);
}

void
cpu_exg (sim_cpu *cpu, uint8_t code)
{
  uint8_t r1, r2;
  uint16_t src1;
  uint16_t src2;

  r1 = (code >> 4) & 0x07;
  r2 = code & 0x07;
  if (code & 0x80)
    {
      src1 = cpu_get_src_reg (cpu, r1);
      src2 = cpu_get_src_reg (cpu, r2);
      if (r2 == 1 || r2 == 2)
        src2 |= 0xff00;
      
      cpu_set_dst_reg (cpu, r2, src1);
      cpu_set_dst_reg (cpu, r1, src2);
    }
  else
    {
      src1 = cpu_get_src_reg (cpu, r1);

      /* Sign extend the 8-bit registers (A, B, CCR).  */
      if ((r1 == 0 || r1 == 1 || r1 == 2) && (src1 & 0x80))
        src1 |= 0xff00;

      cpu_set_dst_reg (cpu, r2, src1);
    }
}

/* Handle special instructions.  */
void
cpu_special (sim_cpu *cpu, enum M6811_Special special)
{
  switch (special)
    {
    case M6811_RTI:
      {
        uint8_t ccr;

        ccr = cpu_m68hc11_pop_uint8 (cpu);
        cpu_set_ccr (cpu, ccr);
        cpu_set_d (cpu, cpu_m68hc11_pop_uint16 (cpu));
        cpu_set_x (cpu, cpu_m68hc11_pop_uint16 (cpu));
        cpu_set_y (cpu, cpu_m68hc11_pop_uint16 (cpu));
        cpu_set_pc (cpu, cpu_m68hc11_pop_uint16 (cpu));
	cpu_return (cpu);
        break;
      }

    case M6812_RTI:
      {
        uint8_t ccr;

        ccr = cpu_m68hc12_pop_uint8 (cpu);
        cpu_set_ccr (cpu, ccr);
        cpu_set_d (cpu, cpu_m68hc12_pop_uint16 (cpu));
        cpu_set_x (cpu, cpu_m68hc12_pop_uint16 (cpu));
        cpu_set_y (cpu, cpu_m68hc12_pop_uint16 (cpu));
        cpu_set_pc (cpu, cpu_m68hc12_pop_uint16 (cpu));
	cpu_return (cpu);
        break;
      }
      
    case M6811_WAI:
      /* In the ELF-start mode, we are in a special mode where
	 the WAI corresponds to an exit.  */
      if (cpu->cpu_use_elf_start)
        {
          cpu_set_pc (cpu, cpu->cpu_insn_pc);
          sim_engine_halt (CPU_STATE (cpu), cpu,
                           NULL, NULL_CIA, sim_exited,
                           cpu_get_d (cpu));
          return;
        }
      /* SCz: not correct... */
      cpu_push_all (cpu);
      break;
      
    case M6811_SWI:
      interrupts_raise (&cpu->cpu_interrupts, M6811_INT_SWI);
      interrupts_process (&cpu->cpu_interrupts);
      break;
      
    case M6811_EMUL_SYSCALL:
    case M6811_ILLEGAL:
      if (cpu->cpu_emul_syscall)
        {
          uint8_t op = memory_read8 (cpu,
                                   cpu_get_pc (cpu) - 1);
          if (op == 0x41)
            {
	      cpu_set_pc (cpu, cpu->cpu_insn_pc);
	      sim_engine_halt (CPU_STATE (cpu), cpu,
			       NULL, NULL_CIA, sim_exited,
			       cpu_get_d (cpu));
	      return;
            }
          else
            {
              emul_os (op, cpu);
            }
          return;
        }
      
      interrupts_raise (&cpu->cpu_interrupts, M6811_INT_ILLEGAL);
      interrupts_process (&cpu->cpu_interrupts);
      break;

    case M6811_TEST:
    case M6812_BGND:
      {
        SIM_DESC sd;

        sd = CPU_STATE (cpu);

        /* Breakpoint instruction if we are under gdb.  */
        if (STATE_OPEN_KIND (sd) == SIM_OPEN_DEBUG)
          {
            cpu->cpu_regs.pc --;
            sim_engine_halt (CPU_STATE (cpu), cpu,
                             0, cpu_get_pc (cpu), sim_stopped,
                             SIM_SIGTRAP);
          }
        /* else this is a nop but not in test factory mode.  */
        break;
      }

    case M6812_IDIVS:
      {
        int32_t src1 = (int16_t) cpu_get_d (cpu);
        int32_t src2 = (int16_t) cpu_get_x (cpu);

        if (src2 == 0)
          {
            cpu_set_ccr_C (cpu, 1);
          }
        else
          {
            cpu_set_d (cpu, src1 % src2);
            src1 = src1 / src2;
            cpu_set_x (cpu, src1);
            cpu_set_ccr_C (cpu, 0);
            cpu_set_ccr_Z (cpu, src1 == 0);
            cpu_set_ccr_N (cpu, src1 & 0x8000);
            cpu_set_ccr_V (cpu, src1 >= 32768 || src1 < -32768);
          }
      }
      break;
      
    case M6812_EDIV:
      {
        uint32_t src1 = (uint32_t) cpu_get_x (cpu);
        uint32_t src2 = (uint32_t) (cpu_get_y (cpu) << 16)
          | (uint32_t) (cpu_get_d (cpu));

        if (src1 == 0)
          {
            cpu_set_ccr_C (cpu, 1);
          }
        else
          {
            cpu_set_ccr_C (cpu, 0);
            cpu_set_d (cpu, src2 % src1);
            src2 = src2 / src1;
            cpu_set_y (cpu, src2);
            cpu_set_ccr_Z (cpu, src2 == 0);
            cpu_set_ccr_N (cpu, (src2 & 0x8000) != 0);
            cpu_set_ccr_V (cpu, (src2 & 0xffff0000) != 0);
          }
      }
      break;
      
    case M6812_EDIVS:
      {
        int32_t src1 = (int16_t) cpu_get_x (cpu);
        int32_t src2 = (uint32_t) (cpu_get_y (cpu) << 16)
          | (uint32_t) (cpu_get_d (cpu));

        if (src1 == 0)
          {
            cpu_set_ccr_C (cpu, 1);
          }
        else
          {
            cpu_set_ccr_C (cpu, 0);
            cpu_set_d (cpu, src2 % src1);
            src2 = src2 / src1;
            cpu_set_y (cpu, src2);
            cpu_set_ccr_Z (cpu, src2 == 0);
            cpu_set_ccr_N (cpu, (src2 & 0x8000) != 0);
            cpu_set_ccr_V (cpu, src2 > 32767 || src2 < -32768);
          }
      }
      break;      

    case M6812_EMULS:
      {
        int32_t src1, src2;

        src1 = (int16_t) cpu_get_d (cpu);
        src2 = (int16_t) cpu_get_y (cpu);
        src1 = src1 * src2;
        cpu_set_d (cpu, src1 & 0x0ffff);
        cpu_set_y (cpu, src1 >> 16);
        cpu_set_ccr_Z (cpu, src1 == 0);
        cpu_set_ccr_N (cpu, (src1 & 0x80000000) != 0);
        cpu_set_ccr_C (cpu, (src1 & 0x00008000) != 0);
      }
      break;
      
    case M6812_EMACS:
      {
        int32_t src1, src2;
        uint16_t addr;
        
        addr = cpu_fetch16 (cpu);
        src1 = (int16_t) memory_read16 (cpu, cpu_get_x (cpu));
        src2 = (int16_t) memory_read16 (cpu, cpu_get_y (cpu));
        src1 = src1 * src2;
        src2 = (((uint32_t) memory_read16 (cpu, addr)) << 16)
          | (uint32_t) memory_read16 (cpu, addr + 2);

        memory_write16 (cpu, addr, (src1 + src2) >> 16);
        memory_write16 (cpu, addr + 2, (src1 + src2));

        
      }
      break;

    case M6812_CALL:
      {
        uint8_t page;
        uint16_t addr;

        addr = cpu_fetch16 (cpu);
        page = cpu_fetch8 (cpu);

        cpu_m68hc12_push_uint16 (cpu, cpu_get_pc (cpu));
        cpu_m68hc12_push_uint8 (cpu, cpu_get_page (cpu));

        cpu_set_page (cpu, page);
        cpu_set_pc (cpu, addr);
      }
      break;

    case M6812_CALL_INDIRECT:
      {
        uint8_t code;
        uint16_t addr;
        uint8_t page;

        code = memory_read8 (cpu, cpu_get_pc (cpu));
        /* Indirect addressing call has the page specified in the
           memory location pointed to by the address.  */
        if ((code & 0xE3) == 0xE3)
          {
            addr = cpu_get_indexed_operand_addr (cpu, 0);
            page = memory_read8 (cpu, addr + 2);
            addr = memory_read16 (cpu, addr);
          }
        else
          {
            /* Otherwise, page is in the opcode.  */
            addr = cpu_get_indexed_operand16 (cpu, 0);
            page = cpu_fetch8 (cpu);
          }
        cpu_m68hc12_push_uint16 (cpu, cpu_get_pc (cpu));
        cpu_m68hc12_push_uint8 (cpu, cpu_get_page (cpu));
        cpu_set_page (cpu, page);
        cpu_set_pc (cpu, addr);
      }
      break;

    case M6812_RTC:
      {
        uint8_t page = cpu_m68hc12_pop_uint8 (cpu);
        uint16_t addr = cpu_m68hc12_pop_uint16 (cpu);

        cpu_set_page (cpu, page);
        cpu_set_pc (cpu, addr);
      }
      break;
      
    case M6812_ETBL:
    default:
      sim_engine_halt (CPU_STATE (cpu), cpu, NULL,
                       cpu_get_pc (cpu), sim_stopped,
                       SIM_SIGILL);
      break;
    }
}


void
cpu_single_step (sim_cpu *cpu)
{
  cpu->cpu_current_cycle = 0;
  cpu->cpu_insn_pc = cpu_get_pc (cpu);

  /* Handle the pending interrupts.  If an interrupt is handled,
     treat this as an single step.  */
  if (interrupts_process (&cpu->cpu_interrupts))
    {
      cpu->cpu_absolute_cycle += cpu->cpu_current_cycle;
      return;
    }
  
  /*  printf("PC = 0x%04x\n", cpu_get_pc (cpu));*/
  cpu->cpu_interpretor (cpu);
  cpu->cpu_absolute_cycle += cpu->cpu_current_cycle;
}

/* VARARGS */
void
sim_memory_error (sim_cpu *cpu, SIM_SIGNAL excep,
		  uint16_t addr, const char *message, ...)
{
  char buf[1024];
  va_list args;

  va_start (args, message);
  vsprintf (buf, message, args);
  va_end (args);

  sim_io_printf (CPU_STATE (cpu), "%s\n", buf);
  cpu_memory_exception (cpu, excep, addr, buf);
}


void
cpu_memory_exception (sim_cpu *cpu, SIM_SIGNAL excep,
                      uint16_t addr, const char *message)
{
  if (cpu->cpu_running == 0)
    return;

  cpu_set_pc (cpu, cpu->cpu_insn_pc);
  sim_engine_halt (CPU_STATE (cpu), cpu, NULL,
                   cpu_get_pc (cpu), sim_stopped, excep);
  
#if 0
  cpu->mem_exception = excep;
  cpu->fault_addr    = addr;
  cpu->fault_msg     = strdup (message);

  if (cpu->cpu_use_handler)
    {
      longjmp (&cpu->cpu_exception_handler, 1);
    }
  (* cpu->callback->printf_filtered)
    (cpu->callback, "Fault at 0x%04x: %s\n", addr, message);
#endif
}

void
cpu_info (SIM_DESC sd, sim_cpu *cpu)
{
  sim_io_printf (sd, "CPU info:\n");
  sim_io_printf (sd, "  Absolute cycle: %s\n",
                 cycle_to_string (cpu, cpu->cpu_absolute_cycle,
                                  PRINT_TIME | PRINT_CYCLE));
  
  sim_io_printf (sd, "  Syscall emulation: %s\n",
                 cpu->cpu_emul_syscall ? "yes, via 0xcd <n>" : "no");
  sim_io_printf (sd, "  Memory errors detection: %s\n",
                 cpu->cpu_check_memory ? "yes" : "no");
  sim_io_printf (sd, "  Stop on interrupt: %s\n",
                 cpu->cpu_stop_on_interrupt ? "yes" : "no");
}