Flash memory problem

Hello, is it true that I cannot write 1MB of data into flash memory (4M)?

I am using Altera DE2 Board. My code is as follow:

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# include <stdio.h># include <stdlib.h># include <unistd.h># include "altera_avalon_pio_regs.h"# include "system.h"# include "alt_types.h"# include "sys/alt_dma.h"# include "sys/alt_flash.h" # include "sys/alt_flash_dev.h"

# define loop 262144# define size 1048576

int main ()

{

alt_flash_fd* fd;

int ret_code, i;

int *src_ptr;

int *dest_ptr;

src_ptr = SDRAM_BASE + 0x200000; //Location of data written in SDRAM

dest_ptr = EXT_FLASH_BASE; //Location of data written in flash

//Open flash

fd = alt_flash_open_dev(EXT_FLASH_NAME);

if(fd!=NULL)

{

//Generate data into SDRAM

for(i=0;i<loop;i++)

{

IOWR(src_ptr, i, i);

}

//Write data into flash

ret_code = alt_write_flash(fd, 0, src_ptr, size);

if(ret_code != 0)

{

printf("Error writing into flash: %d\n", ret_code);

exit(1);

}

//Read from flash

for(i=0;i<loop;i++)

{

printf("Value at %X is %d, written at is %d\n", dest_ptr, *dest_ptr, IORD(src_ptr, i));

dest_ptr++;

}

}else

{

printf("Unable to open flash\n");

exit(1);

}

alt_flash_close_dev(fd);

return 0;

}

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I keep on getting error msg: Cannot write into flash and the error code is -5. pls help me. i am not sure whether is my coding problem or writing 1MB into flash is a special case. pls help! thanks!