diff --git a/src/main/scala/backBoard/Qei.scala b/src/main/scala/backBoard/Qei.scala
index f9e0892..faae8b3 100644
--- a/src/main/scala/backBoard/Qei.scala
+++ b/src/main/scala/backBoard/Qei.scala
@@ -43,7 +43,7 @@ trait BackBoardSlvQei{ this: BackBoardSlvLocal =>
   val isOverflow = for( i <- 0 until 2 ) yield { Wire(Bool()) } 
 
   val isCounter32Flip = for( i <- 0 until 2 ) yield { RegNext( counter(i).extract(32)) =/= counter(i).extract(32) }
-  val isCounter31Flip = for( i <- 0 until 2 ) yield { RegNext( counter(i).extract(31)) =/= counter(i).extract(31) }
+  val isCounter31Flip = for( i <- 0 until 2 ) yield { (RegNext( counter(i).extract(31)) =/= counter(i).extract(31)) & (RegNext( counter(i).extract(32)) === counter(i).extract(32)) }
 
 
   for( i <- 0 until 2 ){
@@ -61,78 +61,29 @@ trait BackBoardSlvQei{ this: BackBoardSlvLocal =>
       when(isEnable(i)){
         when(~is2Phase(i)){ //A Phase only
           when( RegNext( phaseA(i) ) & ~phaseA(i) ){
-            when( isSetVal(i) & isCounter32Flip(i) ){
-              isOverflow(i) := true.B
-            } .otherwise{
+              counter(i) := counter(i) + 1.U
+          }
+
+          isOverflow(i) := isSetVal(i) & isCounter32Flip(i)
+
+        } .otherwise{ //AB Phase
+
+          when( invDirect(i) ) {
+            when(isAdvA(i)){
+              counter(i) := counter(i) - 1.U
+            } .elsewhen(isAdvB(i)){
               counter(i) := counter(i) + 1.U
             }
-          }
-        } .otherwise{ //AB Phase
-          when( isMiss(i) ){
-            printf("Warning! QEI Miss one pulse!\n")
-          } .elsewhen( isAdvA(i) ){
-            when( isSign(i) ) {
-              when( invDirect(i) ){
-                when( isSetVal(i) & isCounter31Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) - 1.U
-                }
-              } .otherwise{
-                when( isSetVal(i) & isCounter31Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) + 1.U
-                }
-              }
-            } .otherwise{
-              when( invDirect(i) ){
-                when( isSetVal(i) & isCounter32Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) - 1.U
-                }
-              } .otherwise{
-                when( isSetVal(i) & isCounter32Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) + 1.U
-                }
-              }
+          } .otherwise{ //~invDirect(i)
+            when(isAdvA(i)){
+              counter(i) := counter(i) + 1.U
+            } .elsewhen(isAdvB(i)){
+              counter(i) := counter(i) - 1.U
             }
-          } .elsewhen( isAdvB(i) ){
-            when( isSign(i) ) {
-              when( invDirect(i) ){
-                when( isSetVal(i) & isCounter31Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) + 1.U
-                }
-              } .otherwise{
-                when( isSetVal(i) & isCounter31Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) - 1.U
-                }
-              }
-            } .otherwise{
-              when( invDirect(i) ){
-                when( isSetVal(i) & isCounter32Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) + 1.U
-                }
-              } .otherwise{
-                when( isSetVal(i) & isCounter32Flip(i) ){
-                  isOverflow(i) := true.B
-                } .otherwise{
-                  counter(i) := counter(i) - 1.U
-                }
-              }
-            }
-          } .otherwise{
-            // assert( isKeep(i) )
           }
+
+          isOverflow(i) :=
+            Mux( isSign(i), isSetVal(i) & isCounter31Flip(i), isSetVal(i) & isCounter32Flip(i) )
         }
         
       } .otherwise{ //~isEnable