diff --git a/src/main/scala/backBoard/shin/SMUnit.scala b/src/main/scala/backBoard/shin/SMUnit.scala
index dbdfd8a..d761ee0 100644
--- a/src/main/scala/backBoard/shin/SMUnit.scala
+++ b/src/main/scala/backBoard/shin/SMUnit.scala
@@ -85,10 +85,11 @@ abstract class SMUnitBase(depth: Int = 4) extends Module {
     ( (rPtr(log2Ceil(depth)-1, 0)) === i.U ) -> io.sram(i).rd.datar
   })
 
-  val cnt = RegInit(0.U((log2Ceil(depth)).W)); io.cnt := cnt
+  val cnt = RegInit(0.U((log2Ceil(depth+1)).W)); io.cnt := cnt
 
   when( io.enq & ~isFull ){
     cnt := cnt + 1.U
+    assert(cnt =/= depth.U)
   } .elsewhen( io.deq & ~isEmpty ){
     cnt := cnt - 1.U
     assert(cnt =/= 0.U)