diff --git a/portable/GCC/ATmegaxxxx/port.c b/portable/GCC/ATmegaxxxx/port.c
index fe1709788..1373970fc 100644
--- a/portable/GCC/ATmegaxxxx/port.c
+++ b/portable/GCC/ATmegaxxxx/port.c
@@ -38,11 +38,11 @@
  *----------------------------------------------------------*/
 
 /* Start tasks with interrupts enabled. */
-#define portFLAGS_INT_ENABLED                ( (StackType_t) 0x80 )
+#define portFLAGS_INT_ENABLED           ( (StackType_t) 0x80 )
 
 #if defined( portUSE_WDTO)
     #warning "Watchdog Timer used for scheduler."
-    #define    portSCHEDULER_ISR        WDT_vect
+    #define portSCHEDULER_ISR           WDT_vect
 
 #elif defined( portUSE_TIMER0 )
 /* Hardware constants for Timer0. */
@@ -97,6 +97,8 @@ static void prvSetupTimerInterrupt( void );
     Updated to match avr-libc 2.0.0
 */
 
+#if defined( portUSE_WDTO)
+
 static __inline__
 __attribute__ ((__always_inline__))
 void wdt_interrupt_enable (const uint8_t value)
@@ -136,6 +138,7 @@ void wdt_interrupt_enable (const uint8_t value)
         );
     }
 }
+#endif
 
 /*-----------------------------------------------------------*/
 /**
@@ -160,6 +163,8 @@ void wdt_interrupt_enable (const uint8_t value)
     Updated to match avr-libc 2.0.0
 */
 
+#if defined( portUSE_WDTO)
+
 static __inline__
 __attribute__ ((__always_inline__))
 void wdt_interrupt_reset_enable (const uint8_t value)
@@ -199,6 +204,7 @@ void wdt_interrupt_reset_enable (const uint8_t value)
         );
     }
 }
+#endif
 
 /*-----------------------------------------------------------*/
 
diff --git a/portable/GCC/ATmegaxxxx/portmacro.h b/portable/GCC/ATmegaxxxx/portmacro.h
index 80fbbd3fd..ae6ce20cd 100644
--- a/portable/GCC/ATmegaxxxx/portmacro.h
+++ b/portable/GCC/ATmegaxxxx/portmacro.h
@@ -43,11 +43,11 @@ extern "C" {
  */
 
 /* Type definitions. */
-#define portCHAR		char
-#define portFLOAT		float
-#define portDOUBLE		double
-#define portLONG		long
-#define portSHORT		int
+#define portCHAR                    char
+#define portFLOAT                   float
+#define portDOUBLE                  double
+#define portLONG                    long
+#define portSHORT                   int
 
 typedef uint8_t StackType_t;
 typedef int8_t BaseType_t;
@@ -55,16 +55,16 @@ typedef uint8_t UBaseType_t;
 
 #if configUSE_16_BIT_TICKS == 1
     typedef uint16_t TickType_t;
-    #define portMAX_DELAY ( TickType_t ) 0xffff
+    #define portMAX_DELAY           ( TickType_t ) 0xffff
 #else
     typedef uint32_t TickType_t;
-    #define portMAX_DELAY ( TickType_t ) 0xffffffffUL
+    #define portMAX_DELAY           ( TickType_t ) 0xffffffffUL
 #endif
 /*-----------------------------------------------------------*/
 
 /* Critical section management. */
 
-#define portENTER_CRITICAL()    __asm__ __volatile__ (                              \
+#define portENTER_CRITICAL()        __asm__ __volatile__ (                          \
                                         "in __tmp_reg__, __SREG__"        "\n\t"    \
                                         "cli"                             "\n\t"    \
                                         "push __tmp_reg__"                "\n\t"    \
@@ -72,39 +72,44 @@ typedef uint8_t UBaseType_t;
                                         )
 
 
-#define portEXIT_CRITICAL()     __asm__ __volatile__ (                              \
+#define portEXIT_CRITICAL()         __asm__ __volatile__ (                          \
                                         "pop __tmp_reg__"                 "\n\t"    \
                                         "out __SREG__, __tmp_reg__"       "\n\t"    \
                                         ::: "memory"                                \
                                         )
 
 
-#define portDISABLE_INTERRUPTS()        __asm__ __volatile__ ( "cli" ::: "memory")
-#define portENABLE_INTERRUPTS()         __asm__ __volatile__ ( "sei" ::: "memory")
+#define portDISABLE_INTERRUPTS()    __asm__ __volatile__ ( "cli" ::: "memory")
+#define portENABLE_INTERRUPTS()     __asm__ __volatile__ ( "sei" ::: "memory")
 
 /*-----------------------------------------------------------*/
 
 /* Architecture specifics. */
 
 // System Tick  - Scheduler timer
-// Prefer to use the Watchdog timer, but also Timer 0 is ok.
+// Prefer to use the enhanced Watchdog Timer, but also Timer0 is ok.
 
-#define portUSE_WDTO            WDTO_15MS       // portUSE_WDTO to use the Watchdog Timer for xTaskIncrementTick
+#if defined(WDIE) && defined(WDIF)              // Enhanced WDT with interrupt capability
 
-/* Watchdog period options:     WDTO_15MS
-                                WDTO_30MS
-                                WDTO_60MS
-                                WDTO_120MS
-                                WDTO_250MS
-                                WDTO_500MS
+#define portUSE_WDTO                WDTO_15MS   // portUSE_WDTO to use the Watchdog Timer for xTaskIncrementTick
 
+/* Watchdog period options:         WDTO_15MS
+                                    WDTO_30MS
+                                    WDTO_60MS
+                                    WDTO_120MS
+                                    WDTO_250MS
+                                    WDTO_500MS
+                                    WDTO_1S
+                                    WDTO_2S
 */
 
-#if !defined( portUSE_WDTO )
+#else
+
 #define portUSE_TIMER0                          // portUSE_TIMER0 to use 8 bit Timer0 for xTaskIncrementTick
+
 #endif
 
-#define portSTACK_GROWTH                ( -1 )
+#define portSTACK_GROWTH            ( -1 )
 
 /* Timing for the scheduler.
  * Watchdog Timer is 128kHz nominal,
@@ -112,23 +117,23 @@ typedef uint8_t UBaseType_t;
  * from data sheet.
  */
 #if defined( portUSE_WDTO )
-#define portTICK_PERIOD_MS              ( (TickType_t) _BV( portUSE_WDTO + 4 ) )    // Inaccurately assuming 128 kHz Watchdog Timer.
+#define portTICK_PERIOD_MS          ( (TickType_t) _BV( portUSE_WDTO + 4 ) )    // Inaccurately assuming 128 kHz Watchdog Timer.
 #else
-#define portTICK_PERIOD_MS              ( ( TickType_t ) 1000 / configTICK_RATE_HZ )
+#define portTICK_PERIOD_MS          ( ( TickType_t ) 1000 / configTICK_RATE_HZ )
 #endif
 
-#define portBYTE_ALIGNMENT              1
-#define portNOP()                       __asm__ __volatile__ ( "nop" );
+#define portBYTE_ALIGNMENT          1
+#define portNOP()                   __asm__ __volatile__ ( "nop" );
 /*-----------------------------------------------------------*/
 
 /* Kernel utilities. */
-extern void vPortYield( void )          __attribute__ ( ( naked ) );
-#define portYIELD()                     vPortYield()
+extern void vPortYield( void )      __attribute__ ( ( naked ) );
+#define portYIELD()                 vPortYield()
 /*-----------------------------------------------------------*/
 
 #if defined(__AVR_ATmega2560__) || defined(__AVR_ATmega2561__)
 /* Task function macros as described on the FreeRTOS.org WEB site. */
-// Add .lowtext tag for the linker for ATmega2560 and ATmega2561. To make sure they are loaded in low memory.
+// Add .lowtext tag from the linker script avr6.x for ATmega2560 and ATmega2561. To make sure they are loaded in low memory.
 #define portTASK_FUNCTION_PROTO( vFunction, pvParameters ) void vFunction( void *pvParameters ) __attribute__ ((section (".lowtext")))
 #else
 #define portTASK_FUNCTION_PROTO( vFunction, pvParameters ) void vFunction( void *pvParameters )