failed to use printf when use uart receiveing interrupt

hello~~~~~~~~

my tool is quartus 9.0sp2 and ide9.0sp2. when i use uart receiving interrupt,i can not use "prinft" to print anything .if i use the "printf",the uart will go wrong.the following is my testing c code.any idea,helps.thanks all!!

# include <stdio.h> # include <string.h># include <system.h># include "altera_avalon_uart_regs.h"# include "altera_avalon_uart.h" # include "alt_types.h" # include "sys/alt_irq.h" # include "altera_avalon_pio_regs.h"

unsigned char flag=0;

void Uart_send(unsigned char data)

{

alt_u16 status;

status=IORD_ALTERA_AVALON_UART_STATUS(UART_0_BASE);

while(!(status&0x0040))

status=IORD_ALTERA_AVALON_UART_STATUS(UART_0_BASE);

IOWR_ALTERA_AVALON_UART_TXDATA(UART_0_BASE,data);

}

void Uart_send_n(unsigned char *ptr,unsigned char n)

{

for(;n>0;n--)

{

Uart_send(*ptr);

ptr++;

}

}

int Uart_receive(void)

{

alt_u16 status;

int temp;

status=IORD_ALTERA_AVALON_UART_STATUS(UART_0_BASE);

while(!(status&0x0080))

status=IORD_ALTERA_AVALON_UART_STATUS(UART_0_BASE);

temp=IORD_ALTERA_AVALON_UART_RXDATA(UART_0_BASE);

return temp;

}

void Uart_ISR(void * context,alt_u32 id)

{

unsigned char temp;

temp=IORD_ALTERA_AVALON_UART_RXDATA(UART_0_BASE);

Uart_send(temp);

flag=1;

}

void Uart_init()

{

IOWR_ALTERA_AVALON_UART_CONTROL(UART_0_BASE, 0x80);

IOWR_ALTERA_AVALON_UART_STATUS(UART_0_BASE, 0x0);

//IOWR_ALTERA_AVALON_UART_RXDATA(UART_0_BASE, 0x0);

alt_irq_register(UART_0_IRQ,0,Uart_ISR}

int main()

{

//printf("test uart");//can not use printf here,why?

Uart_init();

while(1)

{ if(flag==1)

{flag=0;

//printf("uart received data");//still can not use printf,or will go wrong

}

}

return 0;

}