diff --git a/FreeModbus/modbus/functions/mbfunccoils_m.c b/FreeModbus/modbus/functions/mbfunccoils_m.c
index 4d7dd38..9a69322 100644
--- a/FreeModbus/modbus/functions/mbfunccoils_m.c
+++ b/FreeModbus/modbus/functions/mbfunccoils_m.c
@@ -80,7 +80,7 @@ eMBMasterReqReadCoils( UCHAR ucSndAddr, USHORT usCoilAddr, USHORT usNCoils ,LONG
     UCHAR                 *ucMBFrame;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
@@ -167,7 +167,7 @@ eMBMasterReqWriteCoil( UCHAR ucSndAddr, USHORT usCoilAddr, USHORT usCoilData, LO
     UCHAR                 *ucMBFrame;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( usCoilAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else if ( ( usCoilData != 0xFF00 ) && ( usCoilData != 0x0000 ) ) eErrStatus = MB_MRE_ILL_ARG;
     else
@@ -249,7 +249,7 @@ eMBMasterReqWriteMultipleCoils( UCHAR ucSndAddr,
     UCHAR                  ucByteCount;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else if ( usNCoils > MB_PDU_REQ_WRITE_MUL_COILCNT_MAX ) eErrStatus = MB_MRE_ILL_ARG;
     else
diff --git a/FreeModbus/modbus/functions/mbfuncdisc_m.c b/FreeModbus/modbus/functions/mbfuncdisc_m.c
index 1614858..0aca128 100644
--- a/FreeModbus/modbus/functions/mbfuncdisc_m.c
+++ b/FreeModbus/modbus/functions/mbfuncdisc_m.c
@@ -65,7 +65,7 @@ eMBMasterReqReadDiscreteInputs( UCHAR ucSndAddr, USHORT usDiscreteAddr, USHORT u
     UCHAR                 *ucMBFrame;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
diff --git a/FreeModbus/modbus/functions/mbfuncholding_m.c b/FreeModbus/modbus/functions/mbfuncholding_m.c
index cce53c0..25778a0 100644
--- a/FreeModbus/modbus/functions/mbfuncholding_m.c
+++ b/FreeModbus/modbus/functions/mbfuncholding_m.c
@@ -92,7 +92,7 @@ eMBMasterReqWriteHoldingRegister( UCHAR ucSndAddr, USHORT usRegAddr, USHORT usRe
     UCHAR                 *ucMBFrame;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
@@ -151,7 +151,7 @@ eMBMasterReqWriteMultipleHoldingRegister( UCHAR ucSndAddr,
     USHORT                 usRegIndex = 0;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
@@ -233,7 +233,7 @@ eMBMasterReqReadHoldingRegister( UCHAR ucSndAddr, USHORT usRegAddr, USHORT usNRe
     UCHAR                 *ucMBFrame;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
@@ -309,7 +309,7 @@ eMBMasterReqReadWriteMultipleHoldingRegister( UCHAR ucSndAddr,
     USHORT                 usRegIndex = 0;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
diff --git a/FreeModbus/modbus/functions/mbfuncinput_m.c b/FreeModbus/modbus/functions/mbfuncinput_m.c
index 9574bd1..542275c 100644
--- a/FreeModbus/modbus/functions/mbfuncinput_m.c
+++ b/FreeModbus/modbus/functions/mbfuncinput_m.c
@@ -65,7 +65,7 @@ eMBMasterReqReadInputRegister( UCHAR ucSndAddr, USHORT usRegAddr, USHORT usNRegs
     UCHAR                 *ucMBFrame;
     eMBMasterReqErrCode    eErrStatus = MB_MRE_NO_ERR;
 
-    if ( xMBasterRunMutexLock( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
+    if ( xMBasterRunResTake( lTimeOut ) == FALSE ) eErrStatus = MB_MRE_MASTER_BUSY;
     else if ( ucSndAddr > MB_MASTER_TOTAL_SLAVE_NUM ) eErrStatus = MB_MRE_ILL_ARG;
     else
     {
diff --git a/FreeModbus/modbus/include/mbport.h b/FreeModbus/modbus/include/mbport.h
index f065c88..35c841d 100644
--- a/FreeModbus/modbus/include/mbport.h
+++ b/FreeModbus/modbus/include/mbport.h
@@ -92,11 +92,11 @@ BOOL            xMBMasterPortEventPost( eMBMasterEventType eEvent );
 
 BOOL            xMBMasterPortEventGet(  /*@out@ */ eMBMasterEventType * eEvent );
 
-void            vMBasterRunMutexInit( void );
+void            vMBasterRunResInit( void );
 
-BOOL            xMBasterRunMutexLock( int32_t time );
+BOOL            xMBasterRunResTake( int32_t time );
 
-void            vMBasterRunMutexUnlock( void );
+void            vMBasterRunResRelease( void );
 
 /* ----------------------- Serial port functions ----------------------------*/
 
diff --git a/FreeModbus/modbus/mb_m.c b/FreeModbus/modbus/mb_m.c
index 281cbf5..2971f39 100644
--- a/FreeModbus/modbus/mb_m.c
+++ b/FreeModbus/modbus/mb_m.c
@@ -184,8 +184,8 @@ eMBMasterInit( eMBMode eMode, UCHAR ucPort, ULONG ulBaudRate, eMBParity eParity
 		{
 			eMBState = STATE_DISABLED;
 		}
-		/* initialize the Mobus Master mutex */
-		vMBasterRunMutexInit();
+		/* initialize the Mobus Master running resource. */
+		vMBasterRunResInit();
 	}
 	return eStatus;
 }
@@ -319,7 +319,7 @@ eMBMasterPoll( void )
 			}
             /* If master has exception ,Master will send error process.Otherwise the Master is idle.*/
             if (eException != MB_EX_NONE) ( void ) xMBMasterPortEventPost( EV_MASTER_ERROR_PROCESS );
-            else vMBasterRunMutexUnlock();
+            else vMBasterRunResRelease();
             break;
 
         case EV_MASTER_FRAME_SENT:
@@ -329,7 +329,7 @@ eMBMasterPoll( void )
             break;
 
         case EV_MASTER_ERROR_PROCESS:
-        	vMBasterRunMutexUnlock();
+        	vMBasterRunResRelease();
         	break;
         }
     }
diff --git a/FreeModbus/modbus/rtu/mbrtu_m.c b/FreeModbus/modbus/rtu/mbrtu_m.c
index b0ae52b..13e682d 100644
--- a/FreeModbus/modbus/rtu/mbrtu_m.c
+++ b/FreeModbus/modbus/rtu/mbrtu_m.c
@@ -393,7 +393,7 @@ xMBMasterRTUTimerExpired(void)
 
 	vMBMasterPortTimersDisable( );
 	/* If timer mode is convert delay ,then Master is idel now. */
-	if (eMasterCurTimerMode == MB_TMODE_CONVERT_DELAY) vMBasterRunMutexUnlock();
+	if (eMasterCurTimerMode == MB_TMODE_CONVERT_DELAY) vMBasterRunResRelease();
 
 	return xNeedPoll;
 }
diff --git a/FreeModbus/port/portevent_m.c b/FreeModbus/port/portevent_m.c
index 07caa85..70a851d 100644
--- a/FreeModbus/port/portevent_m.c
+++ b/FreeModbus/port/portevent_m.c
@@ -26,9 +26,9 @@
 
 #if MB_MASTER_RTU_ENABLED > 0 || MB_MASTER_ASCII_ENABLED > 0
 /* ----------------------- Variables ----------------------------------------*/
-static eMBMasterEventType eMasterQueuedEvent;
-static BOOL               xMasterEventInQueue;
-static struct rt_mutex    xMasterRunMutex;
+static eMBMasterEventType  eMasterQueuedEvent;
+static BOOL                xMasterEventInQueue;
+static struct rt_semaphore xMasterRunRes;
 
 /* ----------------------- Start implementation -----------------------------*/
 BOOL
@@ -61,37 +61,39 @@ xMBMasterPortEventGet( eMBMasterEventType * eEvent )
 }
 
 /**
- * This function is initialize the Mobus Master mutex .
- * Note:The mutex is define by Operating System.If you not use Opearting System this function can be empty.
+ * This function is initialize the Mobus Master running resource .
+ * Note:The resource is define by Operating System.If you not use Opearting System this function can be empty.
  *
  */
-void vMBasterRunMutexInit( void )
+void vMBasterRunResInit( void )
 {
-	rt_mutex_init(&xMasterRunMutex, "master run", RT_IPC_FLAG_PRIO);
+	rt_sem_init(&xMasterRunRes, "master res", 0x01 , RT_IPC_FLAG_PRIO);
 }
 
 /**
- * This function is lock Mobus Master mutex.
- * Note:The mutex is define by Operating System.If you not use Opearting System this function can be just return TRUE.
+ * This function is take Mobus Master running resource.
+ * Note:The resource is define by Operating System.If you not use Opearting System this function can be just return TRUE.
  *
  * @param lTimeOut the waiting time.
  *
- * @return mutex lock result
+ * @return resource taked result
  */
-BOOL xMBasterRunMutexLock( LONG lTimeOut )
+BOOL xMBasterRunResTake( LONG lTimeOut )
 {
 	/*If waiting time is -1 .It will wait forever */
-	return rt_mutex_take(&xMasterRunMutex, lTimeOut) ? FALSE : TRUE ;
+	return rt_sem_take(&xMasterRunRes, lTimeOut) ? FALSE : TRUE ;
 }
 
 /**
- * This function is unlock Mobus Master mutex.
- * Note:The mutex is define by Operating System.If you not use Opearting System this function can be empty.
+ * This function is release Mobus Master running resource.
+ * Note:The resource is define by Operating System.If you not use Opearting System this function can be empty.
  *
  */
-void vMBasterRunMutexUnlock( void )
+void vMBasterRunResRelease( void )
 {
-	rt_mutex_release(&xMasterRunMutex);
+	/* Clear up resource when need release resource. */
+	rt_sem_control(&xMasterRunRes, RT_IPC_CMD_RESET, 0);
+	rt_sem_release(&xMasterRunRes);
 }
 
 #endif