diff --git a/src/portable/nuvoton/nuc121/dcd_nuc121.c b/src/portable/nuvoton/nuc121/dcd_nuc121.c
index 7edafe5d3..dbc5cd18a 100644
--- a/src/portable/nuvoton/nuc121/dcd_nuc121.c
+++ b/src/portable/nuvoton/nuc121/dcd_nuc121.c
@@ -200,11 +200,10 @@ static void bus_reset(void)
 }
 
 /* centralized location for USBD interrupt enable bit mask */
-#if USE_SOF
-static const uint32_t enabled_irqs = USBD_INTSTS_VBDETIF_Msk | USBD_INTSTS_BUSIF_Msk | USBD_INTSTS_SETUP_Msk | USBD_INTSTS_USBIF_Msk | USBD_INTSTS_SOFIF_Msk;
-#else
-static const uint32_t enabled_irqs = USBD_INTSTS_VBDETIF_Msk | USBD_INTSTS_BUSIF_Msk | USBD_INTSTS_SETUP_Msk | USBD_INTSTS_USBIF_Msk;
-#endif
+enum {
+  ENABLED_IRQS = USBD_INTSTS_VBDETIF_Msk | USBD_INTSTS_BUSIF_Msk | USBD_INTSTS_SETUP_Msk |
+                 USBD_INTSTS_USBIF_Msk   | (USE_SOF ? USBD_INTSTS_SOFIF_Msk : 0)
+};
 
 /*
   NUC121/NUC125/NUC126 TinyUSB API driver implementation
@@ -226,8 +225,8 @@ void dcd_init(uint8_t rhport)
 
   usb_attach();
 
-  USBD->INTSTS = enabled_irqs;
-  USBD->INTEN  = enabled_irqs;
+  USBD->INTSTS = ENABLED_IRQS;
+  USBD->INTEN  = ENABLED_IRQS;
 }
 
 void dcd_int_enable(uint8_t rhport)
@@ -252,10 +251,23 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
   // do it at dcd_edpt0_status_complete()
 }
 
+static void remote_wakeup_delay(void)
+{
+  // try to delay for 1 ms
+  uint32_t count = SystemCoreClock / 1000;
+  while(count--) __NOP();
+}
+
 void dcd_remote_wakeup(uint8_t rhport)
 {
   (void) rhport;
-  USBD->ATTR = USBD_ATTR_RWAKEUP_Msk;
+  // Enable PHY before sending Resume('K') state
+  USBD->ATTR |= USBD_ATTR_PHYEN_Msk;
+  USBD->ATTR |= USBD_ATTR_RWAKEUP_Msk;
+
+  // Per specs: remote wakeup signal bit must be clear within 1-15ms
+  remote_wakeup_delay();
+  USBD->ATTR &=~USBD_ATTR_RWAKEUP_Msk;
 }
 
 bool dcd_edpt_open(uint8_t rhport, tusb_desc_endpoint_t const * p_endpoint_desc)
@@ -367,14 +379,16 @@ void dcd_edpt_clear_stall(uint8_t rhport, uint8_t ep_addr)
 {
   (void) rhport;
   USBD_EP_T *ep = ep_entry(ep_addr, false);
-  ep->CFG |= USBD_CFG_CSTALL_Msk;
+  ep->CFG = (ep->CFG & ~USBD_CFG_DSQSYNC_Msk) | USBD_CFG_CSTALL_Msk;
 }
 
 void dcd_int_handler(uint8_t rhport)
 {
   (void) rhport;
 
-  uint32_t status = USBD->INTSTS;
+  // Mask non-enabled irqs, ex. SOF
+  uint32_t status = USBD->INTSTS & (ENABLED_IRQS | 0xffffff00);
+
 #ifdef SUPPORT_LPM
   uint32_t state = USBD->ATTR & 0x300f;
 #else
@@ -505,7 +519,7 @@ void dcd_int_handler(uint8_t rhport)
   }
 
   /* acknowledge all interrupts */
-  USBD->INTSTS = status & enabled_irqs;
+  USBD->INTSTS = status & ENABLED_IRQS;
 }
 
 // Invoked when a control transfer's status stage is complete.