diff --git a/targets/TARGET_NUVOTON/TARGET_M451/can_api.c b/targets/TARGET_NUVOTON/TARGET_M451/can_api.c
index 42d2975b2d..5c4e0f34bc 100644
--- a/targets/TARGET_NUVOTON/TARGET_M451/can_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M451/can_api.c
@@ -27,14 +27,24 @@
  #include "nu_miscutil.h"
  #include "nu_bitutil.h"
  #include "mbed_critical.h"
+ #include "mbed_error.h"
  
  #define NU_CAN_DEBUG    0
  #define CAN_NUM         1
  
+ /* Reserve Message Object number 31 for Tx */
+#define NU_CAN_MSG_OBJ_NUM_TX   31
+
+/* Max number of message ID filter handle */
+#define NU_CAN_MAXNUM_HNDL      NU_CAN_MSG_OBJ_NUM_TX
+
+/* Convert to string literal */
+#define NU_STR_(X)  #X
+#define NU_STR(X)   NU_STR_(X)
+
  static uintptr_t can_irq_contexts[CAN_NUM] = {0};
  static can_irq_handler can0_irq_handler;
 
-extern uint32_t CAN_IsNewDataReceived(CAN_T *tCAN, uint8_t u8MsgObj);
 extern void CAN_CLR_INT_PENDING_ONLY_BIT(CAN_T *tCAN, uint32_t u32MsgNum);
  
  static const struct nu_modinit_s can_modinit_tab[] = {
@@ -144,7 +154,7 @@ static void can_irq(CANName name, int id)
             can0_irq_handler(can_irq_contexts[id], IRQ_BUS);
         }
     } else if (u8IIDRstatus >= 1 && u8IIDRstatus <= 32) {
-        if (CAN_IsNewDataReceived(can, u8IIDRstatus - 1)) {
+        if ((u8IIDRstatus - 1) != NU_CAN_MSG_OBJ_NUM_TX) {
             can0_irq_handler(can_irq_contexts[id], IRQ_RX);
             CAN_CLR_INT_PENDING_ONLY_BIT(can, (u8IIDRstatus -1));
         } else {
@@ -221,6 +231,9 @@ void can_irq_set(can_t *obj, CanIrqType irq, uint32_t enable)
 
 int can_write(can_t *obj, CAN_Message msg, int cc)
 {
+    /* Unused */
+    (void) cc;
+
     STR_CANMSG_T CMsg;
     
     CMsg.IdType = (uint32_t)msg.format;
@@ -229,7 +242,7 @@ int can_write(can_t *obj, CAN_Message msg, int cc)
     CMsg.DLC = msg.len;
     memcpy((void *)&CMsg.Data[0],(const void *)&msg.data[0], (unsigned int)8);
 
-    return CAN_Transmit((CAN_T *)NU_MODBASE(obj->can), cc, &CMsg);
+    return CAN_Transmit((CAN_T *)NU_MODBASE(obj->can), NU_CAN_MSG_OBJ_NUM_TX, &CMsg);
 }
 
 int can_read(can_t *obj, CAN_Message *msg, int handle)
@@ -293,6 +306,13 @@ int can_mode(can_t *obj, CanMode mode)
 
 int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle)
 {
+    /* Check validity of filter handle */
+    if (handle < 0 || handle >= NU_CAN_MAXNUM_HNDL) {
+        /* NOTE: 0 is ambiguous, error or filter handle 0. */
+        error("Support max " NU_STR(NU_CAN_MAXNUM_HNDL) " CAN filters");
+        return 0;
+    }
+
     uint32_t numask = mask;
     if( numask == 0x0000 )
     {
diff --git a/targets/TARGET_NUVOTON/TARGET_M480/can_api.c b/targets/TARGET_NUVOTON/TARGET_M480/can_api.c
index d16e3ef15b..4312ff1205 100644
--- a/targets/TARGET_NUVOTON/TARGET_M480/can_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M480/can_api.c
@@ -30,10 +30,21 @@
 #include "nu_miscutil.h"
 #include "nu_bitutil.h"
 #include "mbed_critical.h"
+#include "mbed_error.h"
 
 #define NU_CAN_DEBUG    0
 #define CAN_NUM         2
 
+/* Reserve Message Object number 31 for Tx */
+#define NU_CAN_MSG_OBJ_NUM_TX   31
+
+/* Max number of message ID filter handle */
+#define NU_CAN_MAXNUM_HNDL      NU_CAN_MSG_OBJ_NUM_TX
+
+/* Convert to string literal */
+#define NU_STR_(X)  #X
+#define NU_STR(X)   NU_STR_(X)
+
 static uintptr_t can_irq_contexts[CAN_NUM] = {0};
 static can_irq_handler can0_irq_handler;
 static can_irq_handler can1_irq_handler;
@@ -163,7 +174,7 @@ static void can_irq(CANName name, int id)
                 can0_irq_handler(can_irq_contexts[id], IRQ_BUS);
         }
     } else if (u8IIDRstatus >= 1 && u8IIDRstatus <= 32) {
-        if (CAN_IsNewDataReceived(can, u8IIDRstatus - 1)) {
+        if ((u8IIDRstatus - 1) != NU_CAN_MSG_OBJ_NUM_TX) {
             if (id) {
                 can1_irq_handler(can_irq_contexts[id], IRQ_RX);
             }
@@ -272,6 +283,9 @@ void can_irq_set(can_t *obj, CanIrqType irq, uint32_t enable)
 
 int can_write(can_t *obj, CAN_Message msg, int cc)
 {
+    /* Unused */
+    (void) cc;
+
     STR_CANMSG_T CMsg;
 
     CMsg.IdType = (uint32_t)msg.format;
@@ -280,7 +294,7 @@ int can_write(can_t *obj, CAN_Message msg, int cc)
     CMsg.DLC = msg.len;
     memcpy((void *)&CMsg.Data[0],(const void *)&msg.data[0], (unsigned int)8);
 
-    return CAN_Transmit((CAN_T *)(NU_MODBASE(obj->can)), cc, &CMsg);
+    return CAN_Transmit((CAN_T *)(NU_MODBASE(obj->can)), NU_CAN_MSG_OBJ_NUM_TX, &CMsg);
 }
 
 int can_read(can_t *obj, CAN_Message *msg, int handle)
@@ -341,6 +355,13 @@ int can_mode(can_t *obj, CanMode mode)
 
 int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle)
 {
+    /* Check validity of filter handle */
+    if (handle < 0 || handle >= NU_CAN_MAXNUM_HNDL) {
+        /* NOTE: 0 is ambiguous, error or filter handle 0. */
+        error("Support max " NU_STR(NU_CAN_MAXNUM_HNDL) " CAN filters");
+        return 0;
+    }
+
     uint32_t numask = mask;
     if( numask == 0x0000 )
     {
diff --git a/targets/TARGET_NUVOTON/TARGET_NUC472/can_api.c b/targets/TARGET_NUVOTON/TARGET_NUC472/can_api.c
index c940848964..3a258a9843 100644
--- a/targets/TARGET_NUVOTON/TARGET_NUC472/can_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_NUC472/can_api.c
@@ -27,15 +27,25 @@
  #include "nu_miscutil.h"
  #include "nu_bitutil.h"
  #include "mbed_critical.h"
+ #include "mbed_error.h"
  
  #define NU_CAN_DEBUG    0
  #define CAN_NUM         2
  
+ /* Reserve Message Object number 31 for Tx */
+#define NU_CAN_MSG_OBJ_NUM_TX   31
+
+/* Convert to string literal */
+#define NU_STR_(X)  #X
+#define NU_STR(X)   NU_STR_(X)
+
+/* Max number of message ID filter handle */
+#define NU_CAN_MAXNUM_HNDL      NU_CAN_MSG_OBJ_NUM_TX
+
  static uintptr_t can_irq_contexts[CAN_NUM] = {0};
  static can_irq_handler can0_irq_handler;
  static can_irq_handler can1_irq_handler;
 
- extern uint32_t CAN_IsNewDataReceived(CAN_T *tCAN, uint8_t u8MsgObj);
  extern void CAN_CLR_INT_PENDING_ONLY_BIT(CAN_T *tCAN, uint32_t u32MsgNum);
  
  static const struct nu_modinit_s can_modinit_tab[] = {
@@ -158,7 +168,7 @@ static void can_irq(CANName name, int id)
                 can0_irq_handler(can_irq_contexts[id], IRQ_BUS);
         }
     } else if (u8IIDRstatus >= 1 && u8IIDRstatus <= 32) {
-        if (CAN_IsNewDataReceived(can, u8IIDRstatus - 1)) {
+        if ((u8IIDRstatus - 1) != NU_CAN_MSG_OBJ_NUM_TX) {
             if (id) {
                 can1_irq_handler(can_irq_contexts[id], IRQ_RX);
             }
@@ -274,6 +284,9 @@ void can_irq_set(can_t *obj, CanIrqType irq, uint32_t enable)
 
 int can_write(can_t *obj, CAN_Message msg, int cc)
 {
+    /* Unused */
+    (void) cc;
+
     STR_CANMSG_T CMsg;
     
     CMsg.IdType = (uint32_t)msg.format;
@@ -282,7 +295,7 @@ int can_write(can_t *obj, CAN_Message msg, int cc)
     CMsg.DLC = msg.len;
     memcpy((void *)&CMsg.Data[0],(const void *)&msg.data[0], (unsigned int)8);
 
-    return CAN_Transmit((CAN_T *)NU_MODBASE(obj->can), cc, &CMsg);
+    return CAN_Transmit((CAN_T *)NU_MODBASE(obj->can), NU_CAN_MSG_OBJ_NUM_TX, &CMsg);
 }
 
 int can_read(can_t *obj, CAN_Message *msg, int handle)
@@ -346,6 +359,13 @@ int can_mode(can_t *obj, CanMode mode)
 
 int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle)
 {
+    /* Check validity of filter handle */
+    if (handle < 0 || handle >= NU_CAN_MAXNUM_HNDL) {
+        /* NOTE: 0 is ambiguous, error or filter handle 0. */
+        error("Support max " NU_STR(NU_CAN_MAXNUM_HNDL) " CAN filters");
+        return 0;
+    }
+
     return CAN_SetRxMsg((CAN_T *)NU_MODBASE(obj->can), handle , (uint32_t)format, id);
 }