diff --git a/trunk/vreg_ctr.c b/trunk/vreg_ctr.c
index c0bc5da..f58ca08 100644
--- a/trunk/vreg_ctr.c
+++ b/trunk/vreg_ctr.c
@@ -221,14 +221,24 @@ void vreg_ctr_write( u8 adrs, u8 data )
         break;
 
     case ( VREG_C_RTC_ALARM_MIN ):
+        vreg_ctr[adrs] = ( data & 0x7F );
+        rtc_alarm_dirty = 1;
+        break;
+
     case ( VREG_C_RTC_ALARM_HOUR ):
-        vreg_ctr[adrs] = data;
+        vreg_ctr[adrs] = ( data & 0x3F );
         rtc_alarm_dirty = 1;
         break;
 
         // 書くだけでよい
     case ( VREG_C_RTC_ALARM_DAY ):
+        vreg_ctr[adrs] = ( data & 0x3F );
+        break;
+
     case ( VREG_C_RTC_ALARM_MONTH ):
+        vreg_ctr[adrs] = ( data & 0x1F );
+        break;
+
     case ( VREG_C_RTC_ALARM_YEAR ):
         vreg_ctr[adrs] = data;
         break;