diff --git a/core/cd_hw/scd.c b/core/cd_hw/scd.c
index 47ed230..c36c0d4 100644
--- a/core/cd_hw/scd.c
+++ b/core/cd_hw/scd.c
@@ -186,21 +186,31 @@ static void bram_write_word(unsigned int address, unsigned int data)
 /* PCM chip & Gate-Array area                                               */
 /*--------------------------------------------------------------------------*/
 
-static void s68k_poll_detect(reg)
+static void s68k_poll_detect(unsigned int reg_mask)
 {
   /* detect SUB-CPU register polling */
-  if (s68k.poll.detected == (1 << reg))
+  if (s68k.poll.detected & reg_mask)
   {
     if (s68k.cycles <= s68k.poll.cycle)
     {
       if (s68k.pc == s68k.poll.pc)
       {
-        /* stop SUB-CPU until register is modified by MAIN-CPU */
+        /* SUB-CPU polling confirmed ? */
+        if (s68k.poll.detected & 1)
+        {
+          /* idle SUB-CPU until register is modified */
+          s68k.cycles = s68k.cycle_end;
+          s68k.stopped = reg_mask;
 #ifdef LOG_SCD
-        error("s68k stopped from %d cycles\n", s68k.cycles);
+          error("s68k stopped from %d cycles\n", s68k.cycles);
 #endif
-        s68k.cycles = s68k.cycle_end;
-        s68k.stopped = 1 << reg;
+        }
+        else
+        {
+          /* confirm SUB-CPU polling */
+          s68k.poll.detected |= 1;
+          s68k.poll.cycle = s68k.cycles + 392;
+        }
       }
       return;
     }
@@ -208,15 +218,15 @@ static void s68k_poll_detect(reg)
   else
   {
     /* set SUB-CPU register access flag */
-    s68k.poll.detected = 1 << reg;
+    s68k.poll.detected = reg_mask;
   }
 
-  /* restart SUB-CPU polling detection */
+  /* reset SUB-CPU polling detection */
   s68k.poll.cycle = s68k.cycles + 392;
   s68k.poll.pc = s68k.pc;
 }
 
-static void s68k_poll_sync(reg)
+static void s68k_poll_sync(unsigned int reg_mask)
 {
   /* relative MAIN-CPU cycle counter */
   unsigned int cycles = (s68k.cycles * MCYCLES_PER_LINE) / SCYCLES_PER_LINE;
@@ -227,8 +237,8 @@ static void s68k_poll_sync(reg)
     m68k_run(cycles);
   }
 
-  /* MAIN-CPU stopped on register polling ? */
-  if (m68k.stopped & (3 << reg))
+  /* MAIN-CPU idle on register polling ? */
+  if (m68k.stopped & reg_mask)
   {
     /* sync MAIN-CPU with SUB-CPU */
     m68k.cycles = cycles;
@@ -240,9 +250,9 @@ static void s68k_poll_sync(reg)
 #endif
   }
 
-  /* clear CPU register(s) access flags */
-  m68k.poll.detected &= ~(3 << reg);
-  s68k.poll.detected &= ~(3 << reg);
+  /* clear CPU register access flags */
+  s68k.poll.detected &= ~reg_mask;
+  m68k.poll.detected &= ~reg_mask;
 }
 
 static unsigned int scd_read_byte(unsigned int address)
@@ -266,14 +276,14 @@ static unsigned int scd_read_byte(unsigned int address)
   /* Memory Mode */
   if (address == 0xff8003)
   {
-    s68k_poll_detect(0x03);
+    s68k_poll_detect(1<<0x03);
     return scd.regs[0x03>>1].byte.l;
   }
 
   /* MAIN-CPU communication flags */
   if (address == 0xff800e)
   {
-    s68k_poll_detect(0x0e);
+    s68k_poll_detect(1<<0x0e);
     return scd.regs[0x0e>>1].byte.h;
   }
 
@@ -328,7 +338,7 @@ static unsigned int scd_read_byte(unsigned int address)
   /* MAIN-CPU communication words */
   if ((address & 0x1f0) == 0x10)
   {
-    s68k_poll_detect(address & 0x1f);
+    s68k_poll_detect(1 << (address & 0x1f));
   }
 
   /* default registers */
@@ -358,7 +368,7 @@ static unsigned int scd_read_word(unsigned int address)
   /* Memory Mode */
   if (address == 0xff8002)
   {
-    s68k_poll_detect(0x03);
+    s68k_poll_detect(1<<0x03);
     return scd.regs[0x03>>1].w;
   }
 
@@ -418,7 +428,7 @@ static unsigned int scd_read_word(unsigned int address)
       m68k_run(cycles);
     }
 
-    s68k_poll_detect(address & 0x1e);
+    s68k_poll_detect(3 << (address & 0x1e));
   }
 
   /* default registers */
@@ -526,7 +536,7 @@ static void scd_write_byte(unsigned int address, unsigned int data)
 
     case 0x03: /* Memory Mode */
     {
-      s68k_poll_sync(0x02);
+      s68k_poll_sync(1<<0x03);
 
       /* detect MODE & RET bits modifications */
       if ((data ^ scd.regs[0x03 >> 1].byte.l) & 0x05)
@@ -687,7 +697,7 @@ static void scd_write_byte(unsigned int address, unsigned int data)
 
     case 0x0f:  /* SUB-CPU communication flags */
     {
-      s68k_poll_sync(0x0e);
+      s68k_poll_sync(1<<0x0f);
       scd.regs[0x0f>>1].byte.l = data;
       return;
     }
@@ -748,7 +758,7 @@ static void scd_write_byte(unsigned int address, unsigned int data)
       /* SUB-CPU communication words */
       if ((address & 0xf0) == 0x20)
       {
-        s68k_poll_sync((address - 0x10) & 0x1e);
+        s68k_poll_sync(1 << ((address - 0x10) & 0x1f));
       }
 
       /* default registers */
@@ -799,7 +809,7 @@ static void scd_write_word(unsigned int address, unsigned int data)
 
     case 0x02: /* Memory Mode */
     {
-      s68k_poll_sync(0x02);
+      s68k_poll_sync(1<<0x03);
 
       /* detect MODE & RET bits modifications */
       if ((data ^ scd.regs[0x03>>1].byte.l) & 0x05)
@@ -965,7 +975,7 @@ static void scd_write_word(unsigned int address, unsigned int data)
 
     case 0x0e:  /* SUB-CPU communication flags */
     {
-      s68k_poll_sync(0x0e);
+      s68k_poll_sync(1<<0x0f);
 
       /* MSB is read-only */
       scd.regs[0x0f>>1].byte.l = data;
@@ -1032,7 +1042,7 @@ static void scd_write_word(unsigned int address, unsigned int data)
       /* SUB-CPU communication words */
       if ((address & 0xf0) == 0x20)
       {
-        s68k_poll_sync((address - 0x10) & 0x1e);
+        s68k_poll_sync(3 << ((address - 0x10) & 0x1e));
       }
 
       /* default registers */
diff --git a/core/m68k/m68kops.h b/core/m68k/m68kops.h
index 57ca5ce..fd5110e 100644
--- a/core/m68k/m68kops.h
+++ b/core/m68k/m68kops.h
@@ -7220,15 +7220,15 @@ static void m68k_op_dbf_16(void)
   uint res = MASK_OUT_ABOVE_16(*r_dst - 1);
   *r_dst = MASK_OUT_BELOW_16(*r_dst) | res;
 
-  /* reset idle loop detection */
-  m68ki_cpu.poll.detected = 0;
-
   if(res != 0xffff)
   {
     uint offset = OPER_I_16();
     REG_PC -= 2;
     m68ki_branch_16(offset);
     USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+    /* reset idle loop detection */
+    m68ki_cpu.poll.detected = 0;
     return;
   }
   REG_PC += 2;
@@ -7250,6 +7250,9 @@ static void m68k_op_dbhi_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7274,6 +7277,9 @@ static void m68k_op_dbls_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7298,6 +7304,9 @@ static void m68k_op_dbcc_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7322,6 +7331,9 @@ static void m68k_op_dbcs_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7346,6 +7358,9 @@ static void m68k_op_dbne_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7370,6 +7385,9 @@ static void m68k_op_dbeq_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7394,6 +7412,9 @@ static void m68k_op_dbvc_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7418,6 +7439,9 @@ static void m68k_op_dbvs_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7442,6 +7466,9 @@ static void m68k_op_dbpl_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7466,6 +7493,9 @@ static void m68k_op_dbmi_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7490,6 +7520,9 @@ static void m68k_op_dbge_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7514,6 +7547,9 @@ static void m68k_op_dblt_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7538,6 +7574,9 @@ static void m68k_op_dbgt_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
@@ -7562,6 +7601,9 @@ static void m68k_op_dble_16(void)
       REG_PC -= 2;
       m68ki_branch_16(offset);
       USE_CYCLES(CYC_DBCC_F_NOEXP);
+
+      /* reset idle loop detection */
+      m68ki_cpu.poll.detected = 0;
       return;
     }
     REG_PC += 2;
diff --git a/core/mem68k.c b/core/mem68k.c
index 3f1f29a..0004d03 100644
--- a/core/mem68k.c
+++ b/core/mem68k.c
@@ -223,28 +223,31 @@ void z80_write_word(unsigned int address, unsigned int data)
 /* I/O Control                                                              */
 /*--------------------------------------------------------------------------*/
 
-static void m68k_poll_detect(reg)
+static void m68k_poll_detect(unsigned int reg_mask)
 {
   /* detect MAIN-CPU register polling */
-  if (m68k.poll.detected == (1 << reg))
+  if (m68k.poll.detected & reg_mask)
   {
     if (m68k.cycles <= m68k.poll.cycle)
     {
       if (m68k.pc == m68k.poll.pc)
       {
-        /* stop MAIN-CPU until register is modified by SUB-CPU */
-#ifdef LOG_SCD
-        error("m68k stopped from %d cycles\n", m68k.cycles);
-#endif
-        m68k.cycles = m68k.cycle_end;
-        m68k.stopped = 1 << reg;
-
-        /* return to current instruction */
-        do
+        /* MAIN-CPU polling confirmed ? */
+        if (m68k.poll.detected & 1)
         {
-          m68k.pc -= 2;
+          /* idle MAIN-CPU until register is modified */
+          m68k.cycles = m68k.cycle_end;
+          m68k.stopped = reg_mask;
+#ifdef LOG_SCD
+          error("m68k stopped from %d cycles\n", m68k.cycles);
+#endif
+        }
+        else
+        {
+          /* confirm MAIN-CPU polling */
+          m68k.poll.detected |= 1;
+          m68k.poll.cycle = m68k.cycles + 840;
         }
-        while (m68k.ir != *(uint16 *)(m68k.memory_map[(m68k.pc>>16)&0xff].base + (m68k.pc & 0xffff)));
       }
       return;
     }
@@ -252,15 +255,15 @@ static void m68k_poll_detect(reg)
   else
   {
     /* set MAIN-CPU register access flag */
-    m68k.poll.detected = 1 << reg;
+    m68k.poll.detected = reg_mask;
   }
 
-  /* restart MAIN-CPU polling detection */
+  /* reset MAIN-CPU polling detection */
   m68k.poll.cycle = m68k.cycles + 840;
   m68k.poll.pc = m68k.pc;
 }
 
-static void m68k_poll_sync(reg)
+static void m68k_poll_sync(unsigned int reg_mask)
 {
   /* relative SUB-CPU cycle counter */
   unsigned int cycles = (m68k.cycles * SCYCLES_PER_LINE) / MCYCLES_PER_LINE;
@@ -271,8 +274,8 @@ static void m68k_poll_sync(reg)
     s68k_run(cycles);
   }
 
-  /* SUB-CPU stopped on register polling ? */
-  if (s68k.stopped & (3 << reg))
+  /* SUB-CPU idle on register polling ? */
+  if (s68k.stopped & reg_mask)
   {
     /* sync SUB-CPU with MAIN-CPU */
     s68k.cycles = cycles;
@@ -284,9 +287,9 @@ static void m68k_poll_sync(reg)
 #endif
   }
 
-  /* clear CPU register(s) access flags */
-  m68k.poll.detected &= ~(3 << reg);
-  s68k.poll.detected &= ~(3 << reg);
+  /* clear CPU register access flags */
+  s68k.poll.detected &= ~reg_mask;
+  m68k.poll.detected &= ~reg_mask;
 }
 
 unsigned int ctrl_io_read_byte(unsigned int address)
@@ -335,7 +338,7 @@ unsigned int ctrl_io_read_byte(unsigned int address)
         /* Memory Mode */
         if (index == 0x03)
         {
-          m68k_poll_detect(0x03);
+          m68k_poll_detect(1<<0x03);
           return scd.regs[0x03>>1].byte.l;
         }
 
@@ -345,13 +348,13 @@ unsigned int ctrl_io_read_byte(unsigned int address)
           /* relative SUB-CPU cycle counter */
           unsigned int cycles = (m68k.cycles * SCYCLES_PER_LINE) / MCYCLES_PER_LINE;
 
-          /* sync SUB-CPU with MAIN-CPU (Dracula Unleashed w/ Sega CD Model 2 OS ROM) */
+          /* sync SUB-CPU with MAIN-CPU (Dracula Unleashed w/ Sega CD Model 2 Boot ROM) */
           if (!s68k.stopped && (s68k.cycles < cycles))
           {
             s68k_run(cycles);
           }
 
-          m68k_poll_detect(0x0f);
+          m68k_poll_detect(1<<0x0f);
           return scd.regs[0x0f>>1].byte.l;
         }
 
@@ -361,7 +364,7 @@ unsigned int ctrl_io_read_byte(unsigned int address)
           /* SUB-CPU communication words */
           if (index >= 0x20)
           {
-            m68k_poll_detect(index - 0x10);
+            m68k_poll_detect(1 << (index - 0x10));
           }
 
           /* register LSB */
@@ -466,7 +469,7 @@ unsigned int ctrl_io_read_word(unsigned int address)
         /* Memory Mode */
         if (index == 0x02)
         {
-          m68k_poll_detect(0x03);
+          m68k_poll_detect(1<<0x03);
           return scd.regs[0x03>>1].w;
         }
 
@@ -498,7 +501,7 @@ unsigned int ctrl_io_read_word(unsigned int address)
           /* SUB-CPU communication words */
           if (index >= 0x20)
           {
-            m68k_poll_detect(index - 0x10);
+            m68k_poll_detect(3 << (index - 0x10));
           }
           
           return scd.regs[index >> 1].w;
@@ -611,7 +614,7 @@ void ctrl_io_write_byte(unsigned int address, unsigned int data)
                 /* relative SUB-CPU cycle counter */
                 unsigned int cycles = (m68k.cycles * SCYCLES_PER_LINE) / MCYCLES_PER_LINE;
 
-                /* sync SUB-CPU with MAIN-CPU */
+                /* sync SUB-CPU with MAIN-CPU (Earnest Evans, Fhey Area) */
                 if (!s68k.stopped && (s68k.cycles < cycles))
                 {
                   s68k_run(cycles);
@@ -674,7 +677,7 @@ void ctrl_io_write_byte(unsigned int address, unsigned int data)
 
           case 0x03:  /* Memory mode */
           {
-            m68k_poll_sync(0x02);
+            m68k_poll_sync(1<<0x03);
 
             /* PRG-RAM 128k bank mapped to $020000-$03FFFF (resp. $420000-$43FFFF) */
             m68k.memory_map[scd.cartridge.boot + 0x02].base = scd.prg_ram + ((data & 0xc0) << 11);
@@ -726,7 +729,7 @@ void ctrl_io_write_byte(unsigned int address, unsigned int data)
 
           case 0x0e:  /* MAIN-CPU communication flags */
           {
-            m68k_poll_sync(0x0e);
+            m68k_poll_sync(1<<0x0e);
             scd.regs[0x0e>>1].byte.h = data;
             return;
           }
@@ -736,7 +739,7 @@ void ctrl_io_write_byte(unsigned int address, unsigned int data)
             /* MAIN-CPU communication words */
             if ((address & 0x30) == 0x10)
             {
-              m68k_poll_sync(address & 0x1e);
+              m68k_poll_sync(1 << (address & 0x1f));
 
               /* register LSB */
               if (address & 1)
@@ -887,7 +890,7 @@ void ctrl_io_write_word(unsigned int address, unsigned int data)
 
           case 0x02:  /* Memory Mode */
           {
-            m68k_poll_sync(0x02);
+            m68k_poll_sync(1<<0x03);
 
             /* PRG-RAM 128k bank mapped to $020000-$03FFFF (resp. $420000-$43FFFF) */
             m68k.memory_map[scd.cartridge.boot + 0x02].base = scd.prg_ram + ((data & 0xc0) << 11);
@@ -939,7 +942,7 @@ void ctrl_io_write_word(unsigned int address, unsigned int data)
 
           case 0x0e:  /* MAIN-CPU communication flags */
           {
-            m68k_poll_sync(0x0e);
+            m68k_poll_sync(1<<0x0e);
 
             /* LSB is read-only (Mortal Kombat) */
             scd.regs[0x0e>>1].byte.h = data;
@@ -951,7 +954,7 @@ void ctrl_io_write_word(unsigned int address, unsigned int data)
             /* MAIN-CPU communication words */
             if ((address & 0x30) == 0x10)
             {
-              m68k_poll_sync(address & 0x1e);
+              m68k_poll_sync(3 << (address & 0x1e));
               scd.regs[(address >> 1) & 0xff].w = data;
               return;
             }