unsigned portCHAR __low_level_init( void )
{
unsigned portCHAR resetflag = RESF;
unsigned portBASE_TYPE i = 0;         

	portDISABLE_INTERRUPTS();         /* disable global interrupts */                      

	PRCMD = 0x00;                     /* On-chip debug mode */
	PCC  = 0x00;                      /* high speed mode fCPU */
	VSWC = 0x00;
	WDTM2 = 0xF;	                  /* Stop watchdog Timer */
	PLLS = 0x03;                      /* Set PLL stabilisation time */
	PLLON = 1;                        /* activate PLL */
	for( i = 0; i <= 2000; i++ )      /* Wait for stabilisation */
	{
		portNOP();
	}
	while( LOCK )                     /* Wait for PLL frequency stabiliasation */
	{
		portNOP();
	}
	SELPLL = 1;                       /* Set CPU operation to PLL mode */

	return pdTRUE;
}

void vApplicationExceptionRegisterDump( xPortRegisterDump *xRegisterDump )
{
	( void ) xRegisterDump;

	for( ;; )
	{
		portNOP();
	}
}

static void prvTxHandler( void *pvUnused, unsigned portBASE_TYPE uxByteCount )
{
	( void ) pvUnused;
	( void ) uxByteCount;

	/* Nothing to do here.  The Xilinx library function takes care of the
	transmission. */
	portNOP();
}

void vTimer2_ISR_Handler( void )
{
volatile unsigned short usCurrentCount;
static unsigned short usMaxCount = 0;
static unsigned long ulErrorCount = 0UL;

	/* This is the highest priority interrupt in the system, so there is no
	advantage to re-enabling interrupts here.
	
	We use the timer 1 counter value to measure the clock cycles between
	the timer 0 interrupts.  First stop the clock. */
	CMT.CMSTR1.BIT.STR3 = 0;
	portNOP();
	portNOP();
	usCurrentCount = timerTIMER_3_COUNT_VALUE;

	/* Is this the largest count we have measured yet? */
	if( usCurrentCount > usMaxCount )
	{
		if( usCurrentCount > timerEXPECTED_DIFFERENCE_VALUE )
		{
			usMaxJitter = usCurrentCount - timerEXPECTED_DIFFERENCE_VALUE;
		}
		else
		{
			/* This should not happen! */
			ulErrorCount++;
		}
		
		usMaxCount = usCurrentCount;
	}

	/* Used to generate the run time stats. */
	ulHighFrequencyTickCount++;
	
	/* Clear the timer. */
	timerTIMER_3_COUNT_VALUE = 0;
	
	/* Then start the clock again. */
	CMT.CMSTR1.BIT.STR3 = 1;
}

void task2 (void *pvParameters) {

	while(TRUE) {

		printf("Task 2\n");

		taskYIELD();

		for(int i = 0; i < DELAY_LOOP; i++)
			portNOP();
	}

	vTaskDelete(NULL);
}

/**
 * This function should do the actual transmission of the packet. The packet is
 * contained in the pbuf that is passed to the function. This pbuf
 * might be chained.
 *
 * @param netif the lwip network interface structure for this ethernetif
 * @param p the MAC packet to send (e.g. IP packet including MAC addresses and type)
 * @return ERR_OK if the packet could be sent
 *         an err_t value if the packet couldn't be sent
 *
 * @note Returning ERR_MEM here if a DMA queue of your MAC is full can lead to
 *       strange results. You might consider waiting for space in the DMA queue
 *       to become availale since the stack doesn't retry to send a packet
 *       dropped because of memory failure (except for the TCP timers).
 */
static err_t low_level_output(struct netif *netif, struct pbuf *p)
{
    struct pbuf *q;
    u32_t l = 0;
    unsigned char *pcTxData;

#if ETH_PAD_SIZE
    pbuf_header(p, -ETH_PAD_SIZE);			/* drop the padding word */
#endif

    /* Get a DMA buffer into which we can write the data to send. */
    for( int i = 0; i < netifBUFFER_WAIT_ATTEMPTS; i++ ) {
        pcTxData = pcGetNextBuffer();

        if( pcTxData ) {
            break;
        } else {
            vTaskDelay( netifBUFFER_WAIT_DELAY );
        }
    }

    if (pcTxData == NULL) {
        portNOP();

        return ERR_BUF;
    } else {

        for(q = p; q != NULL; q = q->next) {
            /* Send the data from the pbuf to the interface, one pbuf at a
            	 time. The size of the data in each pbuf is kept in the ->len
            	 variable. */

            vTaskSuspendAll();
            memcpy(&pcTxData[l], (u8_t*)q->payload, q->len);
            xTaskResumeAll();
            l += q->len;
        }
    }

    ENET_TxPkt( &pcTxData, l );

#if ETH_PAD_SIZE
    pbuf_header(p, ETH_PAD_SIZE);			/* reclaim the padding word */
#endif

    LINK_STATS_INC(link.xmit);

    return ERR_OK;
}

void vAssertCalled( void )
{
volatile unsigned long ul = 0;

	taskENTER_CRITICAL();
	{
		/* Use the debugger to set ul to a non-zero value in order to step out
		of this function to determine why it was called. */
		while( ul == 0 )
		{
			portNOP();
		}
	}
	taskEXIT_CRITICAL();
}

void vAssertCalled( const char * pcFile, unsigned long ulLine )
{
    volatile unsigned long ul = 0;

    ( void ) pcFile;
    ( void ) ulLine;

    taskENTER_CRITICAL();
    {
        /* Set ul to a non-zero value using the debugger to step out of this
        function. */
        while( ul == 0 ) {
            portNOP();
        }
    }
    taskEXIT_CRITICAL();
}

void vAssertCalled( const char * pcFile, unsigned long ulLine )
{
volatile unsigned long ul = 0;

	( void ) pcFile;
	( void ) ulLine;

	__asm volatile( "di" );
	{
		/* Set ul to a non-zero value using the debugger to step out of this
		function. */
		while( ul == 0 )
		{
			portNOP();
		}
	}
	__asm volatile( "ei" );
}

/*
  Deallocates a mailbox. If there are messages still present in the
  mailbox when the mailbox is deallocated, it is an indication of a
  programming error in lwIP and the developer should be notified.
*/
void sys_mbox_free(sys_mbox_t mbox)
{
	if( uxQueueMessagesWaiting( mbox ) )
	{
		/* Line for breakpoint.  Should never break here! */
		portNOP();
#if SYS_STATS
	    lwip_stats.sys.mbox.err++;
#endif /* SYS_STATS */
			
		// TODO notify the user of failure.
	}

	vQueueDelete( mbox );

#if SYS_STATS
     --lwip_stats.sys.mbox.used;
#endif /* SYS_STATS */
}

unsigned char __low_level_init(void)
{
unsigned char resetflag = RESF;
unsigned char psval = 0;
unsigned portBASE_TYPE i = 0;        

	/* Setup provided by NEC. */

	portDISABLE_INTERRUPTS();         /* disable global interrupts */                      

	PRCMD = 0x00;                     /* On-chip debug mode */
	OCDM = 0x00;
	VSWC = 0x00;                      /* set system wait control register */
	WDTM2 = 0x00;                     /* WDT2 setting */
	PLLON = 0;                        /* PLL stop mode */
	psval = 0x0A | 0x00;
	PRCMD = psval;                    /* set Command Register */
	CKC = psval;                      /* set Clock Control Register */
	PLLS = 0x03;
	psval = 0x80;                     /* Set fXX and fCPU */
	PRCMD = psval;
	PCC = psval;
	PLLON = 1;                        /* activate PLL */
	for( i = 0; i <= 2000; i++ )      /* Wait for stabilisation */
	{
	portNOP();
	}
	while( LOCK )                     /* Wait for PLL frequency stabiliasation */
	{
	;
	}
	SELPLL = 1;                       /* Set PLL mode active */
	RSTOP = 0;                        /* Set fR (enable) */
	BGCE0 = 0;                        /* Set fBRG(disable) */
	psval = 0x00;                     /* Stand-by setting */
	PRCMD = psval;                    /* set Command Register */
	PSC = psval;                      /* set Power Save Control Register */

	return pdTRUE;
}

signed portBASE_TYPE xQueueCRReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait )
{
signed portBASE_TYPE xReturn;

	/* If the queue is already empty we may have to block.  A critical section
	is required to prevent an interrupt adding something to the queue 
	between the check to see if the queue is empty and blocking on the queue. */
	portDISABLE_INTERRUPTS();
	{
		if( prvIsQueueEmpty( pxQueue ) )
		{
			/* There are no messages in the queue, do we want to block or just
			leave with nothing? */			
			if( xTicksToWait > ( portTickType ) 0 )
			{
				/* As this is a co-routine we cannot block directly, but return
				indicating that we need to block. */
				vCoRoutineAddToDelayedList( xTicksToWait, &( pxQueue->xTasksWaitingToReceive ) );
				portENABLE_INTERRUPTS();
				return errQUEUE_BLOCKED;
			}
			else
			{
				portENABLE_INTERRUPTS();
				return errQUEUE_FULL;
			}
		}
	}
	portENABLE_INTERRUPTS();

	portNOP();

	portDISABLE_INTERRUPTS();
	{
		if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
		{
			/* Data is available from the queue. */
			pxQueue->pcReadFrom += pxQueue->uxItemSize;
			if( pxQueue->pcReadFrom >= pxQueue->pcTail )
			{
				pxQueue->pcReadFrom = pxQueue->pcHead;
			}
			--( pxQueue->uxMessagesWaiting );
			memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );

			xReturn = pdPASS;

			/* Were any co-routines waiting for space to become available? */
			if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )
			{
				/* In this instance the co-routine could be placed directly 
				into the ready list as we are within a critical section.  
				Instead the same pending ready list mechansim is used as if
				the event were caused from within an interrupt. */
				if( xCoRoutineRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )
				{
					xReturn = errQUEUE_YIELD;
				}
			}	
		}
		else
		{
			xReturn = pdFAIL;
		}
	}
	portENABLE_INTERRUPTS();

	return xReturn;
}

signed portBASE_TYPE xQueueCRSend( xQueueHandle pxQueue, const void *pvItemToQueue, portTickType xTicksToWait )
{
signed portBASE_TYPE xReturn;
		
	/* If the queue is already full we may have to block.  A critical section
	is required to prevent an interrupt removing something from the queue 
	between the check to see if the queue is full and blocking on the queue. */
	portDISABLE_INTERRUPTS();
	{
		if( prvIsQueueFull( pxQueue ) )
		{
			/* The queue is full - do we want to block or just leave without
			posting? */
			if( xTicksToWait > ( portTickType ) 0 )
			{
				/* As this is called from a coroutine we cannot block directly, but
				return indicating that we need to block. */
				vCoRoutineAddToDelayedList( xTicksToWait, &( pxQueue->xTasksWaitingToSend ) );				
				portENABLE_INTERRUPTS();
				return errQUEUE_BLOCKED;
			}
			else
			{
				portENABLE_INTERRUPTS();
				return errQUEUE_FULL;
			}
		}
	}
	portENABLE_INTERRUPTS();
		
	portNOP();

	portDISABLE_INTERRUPTS();
	{
		if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )
		{
			/* There is room in the queue, copy the data into the queue. */			
			prvCopyQueueData( pxQueue, pvItemToQueue );		
			xReturn = pdPASS;

			/* Were any co-routines waiting for data to become available? */
			if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )
			{
				/* In this instance the co-routine could be placed directly 
				into the ready list as we are within a critical section.  
				Instead the same pending ready list mechansim is used as if
				the event were caused from within an interrupt. */
				if( xCoRoutineRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
				{
					/* The co-routine waiting has a higher priority so record 
					that a yield might be appropriate. */
					xReturn = errQUEUE_YIELD;
				}
			}
		}
		else
		{
			xReturn = errQUEUE_FULL;
		}
	}
	portENABLE_INTERRUPTS();

	return xReturn;
}

//.........这里部分代码省略.........
	xRegisterDump.ulR11 = pulStackPointerOnFunctionEntry[ portexR11_STACK_OFFSET ];
	xRegisterDump.ulR12 = pulStackPointerOnFunctionEntry[ portexR12_STACK_OFFSET ];
	xRegisterDump.ulR15_return_address_from_subroutine = pulStackPointerOnFunctionEntry[ portexR15_STACK_OFFSET ];
	xRegisterDump.ulR18 = pulStackPointerOnFunctionEntry[ portexR18_STACK_OFFSET ];
	xRegisterDump.ulR19 = pulStackPointerOnFunctionEntry[ portexR19_STACK_OFFSET ];
	xRegisterDump.ulMSR = pulStackPointerOnFunctionEntry[ portexMSR_STACK_OFFSET ];

	/* Obtain the value of all other registers. */
	xRegisterDump.ulR2_small_data_area = mfgpr( R2 );
	xRegisterDump.ulR13_read_write_small_data_area = mfgpr( R13 );
	xRegisterDump.ulR14_return_address_from_interrupt = mfgpr( R14 );
	xRegisterDump.ulR16_return_address_from_trap = mfgpr( R16 );
	xRegisterDump.ulR17_return_address_from_exceptions = mfgpr( R17 );
	xRegisterDump.ulR20 = mfgpr( R20 );
	xRegisterDump.ulR21 = mfgpr( R21 );
	xRegisterDump.ulR22 = mfgpr( R22 );
	xRegisterDump.ulR23 = mfgpr( R23 );
	xRegisterDump.ulR24 = mfgpr( R24 );
	xRegisterDump.ulR25 = mfgpr( R25 );
	xRegisterDump.ulR26 = mfgpr( R26 );
	xRegisterDump.ulR27 = mfgpr( R27 );
	xRegisterDump.ulR28 = mfgpr( R28 );
	xRegisterDump.ulR29 = mfgpr( R29 );
	xRegisterDump.ulR30 = mfgpr( R30 );
	xRegisterDump.ulR31 = mfgpr( R31 );
	xRegisterDump.ulR1_SP = ( ( uint32_t ) pulStackPointerOnFunctionEntry ) + portexASM_HANDLER_STACK_FRAME_SIZE;
	xRegisterDump.ulEAR = mfear();
	xRegisterDump.ulESR = mfesr();
	xRegisterDump.ulEDR = mfedr();

	/* Move the saved program counter back to the instruction that was executed
	when the exception occurred.  This is only valid for certain types of
	exception. */
	xRegisterDump.ulPC = xRegisterDump.ulR17_return_address_from_exceptions - portexINSTRUCTION_SIZE;

	#if( XPAR_MICROBLAZE_USE_FPU != 0 )
	{
		xRegisterDump.ulFSR = mffsr();
	}
	#else
	{
		xRegisterDump.ulFSR = 0UL;
	}
	#endif

	/* Also fill in a string that describes what type of exception this is.
	The string uses the same ID names as defined in the MicroBlaze standard
	library exception header files. */
	switch( ( uint32_t ) pvExceptionID )
	{
		case XEXC_ID_FSL :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_FSL";
				break;

		case XEXC_ID_UNALIGNED_ACCESS :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_UNALIGNED_ACCESS";
				break;

		case XEXC_ID_ILLEGAL_OPCODE :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_ILLEGAL_OPCODE";
				break;

		case XEXC_ID_M_AXI_I_EXCEPTION :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_M_AXI_I_EXCEPTION or XEXC_ID_IPLB_EXCEPTION";
				break;

		case XEXC_ID_M_AXI_D_EXCEPTION :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_M_AXI_D_EXCEPTION or XEXC_ID_DPLB_EXCEPTION";
				break;

		case XEXC_ID_DIV_BY_ZERO :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_DIV_BY_ZERO";
				break;

		case XEXC_ID_STACK_VIOLATION :
				xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_STACK_VIOLATION or XEXC_ID_MMU";
				break;

		#if( XPAR_MICROBLAZE_USE_FPU != 0 )

			case XEXC_ID_FPU :
						xRegisterDump.pcExceptionCause = ( int8_t * const ) "XEXC_ID_FPU see ulFSR value";
						break;

		#endif /* XPAR_MICROBLAZE_USE_FPU */
	}

	/* vApplicationExceptionRegisterDump() is a callback function that the
	application can optionally define to receive the populated xPortRegisterDump
	structure.  If the application chooses not to define a version of
	vApplicationExceptionRegisterDump() then the weekly defined default
	implementation within this file will be called instead. */
	vApplicationExceptionRegisterDump( &xRegisterDump );

	/* Must not attempt to leave this function! */
	for( ;; )
	{
		portNOP();
	}
}