diff --git a/trunk/bootrom/build/libraries/os/common/os_tick.c b/trunk/bootrom/build/libraries/os/common/os_tick.c
index 2dc66f6..011355b 100644
--- a/trunk/bootrom/build/libraries/os/common/os_tick.c
+++ b/trunk/bootrom/build/libraries/os/common/os_tick.c
@@ -75,7 +75,7 @@ void osInitTick(void)
 
 #ifdef SDK_ARM11
         osStopTimer();
-        osStartTimerWithMSec(1, 0);
+        osStartTimer(OS_TICK_LO_MASK+1, 0);
 #else // SDK_ARM9
         //---- OS reserves OSi_TICK_TIMER timer
         SDK_ASSERT(!i_osIsTimerReserved(OSi_TICK_TIMER));
@@ -131,7 +131,7 @@ static void i_osCountUpTick(void)
     {
 #ifdef SDK_ARM11
         osStopTimer();
-        osStartTimerWithMSec(1, 0);
+        osStartTimer(OS_TICK_LO_MASK+1, 0);
 #else // SDK_ARM9
         osSetTimerControl(OSi_TICK_TIMER, 0);
         osSetTimerCount((OSTimer)OSi_TICK_TIMER, (u16)0);
@@ -157,17 +157,18 @@ static void i_osCountUpTick(void)
  *---------------------------------------------------------------------------*/
 u64 osGetTick(void)
 {
-#ifdef SDK_ARM11
-    return (i_osTickCounter << 32) | reg_OS_WD_COUNT;
-#else // SDK_ARM9
-    vu16    countL;
+    vu32    countL;
     vu64    countH;
 
     OSIntrMode prev = osDisableInterrupts();
     SDK_ASSERT(i_osUseTick);
 
+#ifdef SDK_ARM11
+    countL = reg_OS_TM_COUNT;
+    countH = i_osTickCounter << OS_TICK_HI_SHIFT;
+#else // SDK_ARM9
     countL = *(REGType16 *)((u32)REG_TM0CNT_L_ADDR + OSi_TICK_TIMER * 4);
-    countH = i_osTickCounter & 0xffffffffffffULL;
+    countH = i_osTickCounter;
 
     //---- check if timer interrupt bit is on
     if (reg_OS_IF & OSi_TICK_IE_TIMER && !(countL & 0x8000))
@@ -175,10 +176,12 @@ u64 osGetTick(void)
         countH++;
     }
     
+    countH <<= OS_TICK_HI_SHIFT;
+
+#endif // SDK_ARM9
     (void)osRestoreInterrupts(prev);
 
-    return (countH << 16) | countL;
-#endif // SDK_ARM9
+    return countH | countL;
 }
 
 #ifdef SDK_ARM9
@@ -219,17 +222,17 @@ void osSetTick(u64 count)
 #ifdef SDK_ARM11
     osClearInterruptPending(OSi_TICK_IE_TIMER_ID);
 
-    i_osTickCounter = (u64)(count >> 32);
+    i_osTickCounter = (u64)(count >> OS_TICK_HI_SHIFT);
 
     osStopTimer();
-    osStartTimerWithMSec((u32)count, 0);
+    osStartTimer((u32)(count & OS_TICK_LO_MASK), 0);
 #else // SDK_ARM9
     reg_OS_IF = OSi_TICK_IE_TIMER;
 
-    i_osTickCounter = (u64)(count >> 16);
+    i_osTickCounter = (u64)(count >> OS_TICK_HI_SHIFT);
 
     osSetTimerControl(OSi_TICK_TIMER, 0);
-    osSetTimerCount((OSTimer)OSi_TICK_TIMER, (u16)(count & 0xffff));
+    osSetTimerCount((OSTimer)OSi_TICK_TIMER, (u16)(count & OS_TICK_LO_MASK));
     osSetTimerControl(OSi_TICK_TIMER, (u16)OSi_TICK_TIMERCONTROL);
 #endif // SDK_ARM9
 
diff --git a/trunk/bootrom/include/brom/os/common/tick.h b/trunk/bootrom/include/brom/os/common/tick.h
index 3299c30..832f429 100644
--- a/trunk/bootrom/include/brom/os/common/tick.h
+++ b/trunk/bootrom/include/brom/os/common/tick.h
@@ -45,8 +45,12 @@ extern  void osSetTick( u64 );
 //---- conversion tick count <-> real time count
 #ifdef SDK_ARM11
 #define OS_SYSTEM_CLOCK                HW_CPU_CLOCK
+#define OS_TICK_HI_SHIFT               31               // 2の累乗単位でチック管理するのであれば32は指定できない（ロード値0では割り込み発生せず）
+#define OS_TICK_LO_MASK                ((u32)((1ULL<<OS_TICK_HI_SHIFT)-1))
 #else // SDK_ARM9
 #define OS_SYSTEM_CLOCK                HW_SYSTEM_CLOCK
+#define OS_TICK_HI_SHIFT               16               // ロード値0でも割り込み発生
+#define OS_TICK_LO_MASK                ((u16)((1ULL<<OS_TICK_HI_SHIFT)-1))
 #endif // SDK_ARM9
 
 //---- sec to tick