diff --git a/Source/portable/GCC/PPC405/port.c b/Source/portable/GCC/PPC405/port.c
index 774ad9285..07b90fea5 100644
--- a/Source/portable/GCC/PPC405/port.c
+++ b/Source/portable/GCC/PPC405/port.c
@@ -41,7 +41,7 @@
 */
 
 /*-----------------------------------------------------------
- * Implementation of functions defined in portable.h for the MicroBlaze port.
+ * Implementation of functions defined in portable.h for the PPC405 port.
  *----------------------------------------------------------*/
 
 
@@ -50,7 +50,6 @@
 #include "task.h"
 
 /* Library includes. */
-#include "xexception_l.h"
 #include "xtime_l.h"
 
 /* Standard includes. */
@@ -58,20 +57,17 @@
 
 /*-----------------------------------------------------------*/
 
-#define portCRITICAL_INTERRUPT_ENABLE	( 1UL << 14UL )
-#define portEXTERNAL_INTERRUPT_ENABLE	( 1UL << 16UL )
-#define portMACHINE_CHECK_ENABLE		( 1UL << 19UL )
+#define portCRITICAL_INTERRUPT_ENABLE	( 0UL << 17UL )
+#define portEXTERNAL_INTERRUPT_ENABLE	( 1UL << 15UL )
+#define portMACHINE_CHECK_ENABLE		( 0UL << 12UL )
 #define portINITIAL_MSR		( portCRITICAL_INTERRUPT_ENABLE | portEXTERNAL_INTERRUPT_ENABLE | portMACHINE_CHECK_ENABLE )
 
-
 /*
  */
 static void prvSetupTimerInterrupt( void );
-extern void vStartFirstTask( void );
-/*-----------------------------------------------------------*/
-
-static void prvTickISR( void );
+extern void vPortTickISR( void );
 extern void vPortYield( void );
+extern void vPortStartFirstTask( void );
 
 /* 
  * Initialise the stack of a task to look exactly as if a call to 
@@ -156,13 +152,13 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = 0x00000000UL;	/* CTR. */
 	pxTopOfStack--;
-	*pxTopOfStack = ( portSTACK_TYPE ) vStartFirstTask;	/* LR. */
+	*pxTopOfStack = ( portSTACK_TYPE ) vPortStartFirstTask;	/* LR. */
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* SRR0. */
 	pxTopOfStack--;
 	*pxTopOfStack = portINITIAL_MSR;/* SRR1. */
 	pxTopOfStack--;
-	*pxTopOfStack = ( portSTACK_TYPE ) vStartFirstTask;/* Next LR. */
+	*pxTopOfStack = ( portSTACK_TYPE ) vPortStartFirstTask;/* Next LR. */
 	pxTopOfStack--;
 	*pxTopOfStack = 0x00000000UL;;/* Backchain. */
 //	pxTopOfStack--;
@@ -178,12 +174,14 @@ extern void *pxCurrentTCB;
 	XExc_Init();
 	XExc_mDisableExceptions( XEXC_NON_CRITICAL ) ;	
 
-//	prvSetupTimerInterrupt();
-	XExc_RegisterHandler( XEXC_ID_SYSTEM_CALL, ( XExceptionHandler ) vPortYield, ( void * ) 0 );
-	XExc_mEnableExceptions( XEXC_NON_CRITICAL ) ;
+	prvSetupTimerInterrupt();
+
+	XExc_RegisterHandler( XEXC_ID_SYSTEM_CALL, ( XExceptionHandler ) vPortYield, ( void * ) 0 );
+
+//	XExc_mEnableExceptions( XEXC_NON_CRITICAL );
+
+	vPortStartFirstTask();
 
-	vStartFirstTask();
-	
 	/* Should not get here as the tasks are now running! */
 	return pdFALSE;
 }
@@ -198,11 +196,18 @@ void vPortEndScheduler( void )
 /*
  * Hardware initialisation to generate the RTOS tick.   
  */
+static void prvTickISR( void );
 static void prvSetupTimerInterrupt( void )
 {
 const unsigned portLONG ulInterval = ( ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL );
 
-	XExc_RegisterHandler( XEXC_ID_PIT_INT, ( XExceptionHandler ) prvTickISR, ( void * ) 0 );
+	XTime_PITClearInterrupt();
+	XTime_FITClearInterrupt();
+	XTime_WDTClearInterrupt();
+	XTime_WDTDisableInterrupt();
+	XTime_FITDisableInterrupt();
+
+	XExc_RegisterHandler( XEXC_ID_PIT_INT, ( XExceptionHandler ) vPortTickISR, ( void * ) 0 );
 
 	XTime_PITEnableAutoReload();
 	XTime_PITSetInterval( ulInterval );
@@ -221,9 +226,6 @@ static unsigned portLONG ulTicks = 0;
 		ulTicks = 0;
 	}
 	XTime_PITClearInterrupt();
-	
-	#if configUSE_PREEMPTION == 1
-	#endif
 }
 /*-----------------------------------------------------------*/
 
diff --git a/Source/portable/GCC/PPC405/portasm.s b/Source/portable/GCC/PPC405/portasm.s
index da8d9f6d7..3810a8811 100644
--- a/Source/portable/GCC/PPC405/portasm.s
+++ b/Source/portable/GCC/PPC405/portasm.s
@@ -2,9 +2,11 @@
 
 	.extern pxCurrentTCB
 	.extern vTaskSwitchContext
+	.extern vTaskIncrementTick
 
-	.global vStartFirstTask
+	.global vPortStartFirstTask
 	.global vPortYield
+	.global vPortTickISR
 
 .set portCONTEXT_SIZE, 156
 .set portR0_OFFSET, 152
@@ -196,12 +198,12 @@
 .endm
 
 
-vStartFirstTask:
+vPortStartFirstTask:
 
 	int_epilogue
 	rfi
 
-#vStartFirstTask:
+#vPortStartFirstTask:
 #	portRESTORE_CONTEXT
 #	rfi
 
@@ -214,5 +216,19 @@ vPortYield:
 	portEXIT_SWITCHING_ISR
 	blr
 
-	NOP
-	NOP
+vPortTickISR:
+
+	portENTER_SWITCHING_ISR
+	bl vTaskIncrementTick
+	#if configUSE_PREEMPTION == 1
+		bl vTaskSwitchContext
+	#endif
+
+	# Clear the interrupt
+	lis		R0, 2048
+	mttsr	R0
+
+	portEXIT_SWITCHING_ISR
+	blr
+
+
diff --git a/Source/portable/GCC/PPC405/portmacro.h b/Source/portable/GCC/PPC405/portmacro.h
index dc895d215..5b6be119a 100644
--- a/Source/portable/GCC/PPC405/portmacro.h
+++ b/Source/portable/GCC/PPC405/portmacro.h
@@ -43,6 +43,8 @@
 #ifndef PORTMACRO_H
 #define PORTMACRO_H
 
+#include "xexception_l.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -75,16 +77,19 @@ extern "C" {
 #endif
 /*-----------------------------------------------------------*/	
 
+#define portCRITICAL_NESTING_IN_TCB		1
+
 /* Interrupt control macros. */
-#define portDISABLE_INTERRUPTS()	
-#define portENABLE_INTERRUPTS()		
+#define portDISABLE_INTERRUPTS()		XExc_mDisableExceptions( XEXC_NON_CRITICAL );
+#define portENABLE_INTERRUPTS()			XExc_mEnableExceptions( XEXC_NON_CRITICAL );
+
 /*-----------------------------------------------------------*/
 
 /* Critical section macros. */
-void vPortEnterCritical( void );
-void vPortExitCritical( void );
-#define portENTER_CRITICAL()									
-#define portEXIT_CRITICAL()
+void vTaskEnterCritical( void );
+void vTaskExitCritical( void );
+#define portENTER_CRITICAL()			vTaskEnterCritical()
+#define portEXIT_CRITICAL()				vTaskExitCritical()
 
 /*-----------------------------------------------------------*/