这个程序为什么只有最后读出来的数才是正确的呢？是FLASH没写进去

#include "C2DSP_board_diag_std.h"

#define DATA_OFFSET 0x0
#define DATA_OFFSET1 0x100
#define DATA_OFFSET2 0x200
#define ALT_STDIN "/dev/jtag_uart"
#define EPCS_CONTROLLER_NAME "/dev/epcs_controller"

alt_flash_fd* flash_handle;

int main()
{
int A,B,y=0;
alt_u16 a=10;
alt_u16 b=20;
alt_u16 x=30;
// alt_u16 par[3]={10,20,30};
int *read_data=0;
volatile int *q,*p = 0;
IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE, 0xff); // init leds off
IOWR_ALTERA_AVALON_PIO_DATA(SEVEN_SEG_PIO_BASE, 0xffff); // init hex display off
//向FLASH中写数
flash_handle = alt_flash_open_dev(EPCS_CONTROLLER_NAME);
usleep(10000);
if(flash_handle)
{
printf("open flash device successed!!!\n");
usleep(10000);
alt_write_flash(flash_handle, DATA_OFFSET, &a, 1);
printf( "wirte_data = %d\n", a);
usleep(10000);
alt_write_flash(flash_handle, DATA_OFFSET1, &b, 1);
printf( "wirte_data = %d\n", b);
usleep(10000);
alt_write_flash(flash_handle, DATA_OFFSET2, &x, 1);
printf( "wirte_data = %d\n", x);
usleep(10000);
a=0;b=0;x=0;
alt_read_flash(flash_handle, DATA_OFFSET, &a, 1);
printf("read_data = %d\n", a);
usleep(50000);
alt_read_flash(flash_handle, DATA_OFFSET1, &b, 1);
printf("read_data = %d\n", b);
usleep(50000);
alt_read_flash(flash_handle, DATA_OFFSET2, &x, 1);
printf("read_data = %d\n", x);
usleep(10000);
// alt_write_flash(flash_handle,DATA_OFFSET,par, 3);
/* usleep(10000);
alt_write_flash(flash_handle,0,&a, 1);
usleep(10000);
alt_write_flash(flash_handle,1,&b, 1);
usleep(10000);
alt_write_flash(flash_handle,2,&x, 1);
usleep(10000);

//读取FLASH

// alt_read_flash(flash_handle, DATA_OFFSET, read_data, 3);
alt_read_flash(flash_handle, 0, read_data, 1);
printf(" a= %d\n", *read_data);
usleep(10000);
/* alt_read_flash(flash_handle, 1, read_data, 1);
printf(" b= %d\n", *read_data);
usleep(10000);
alt_read_flash(flash_handle, 2, read_data, 1);
printf(" x= %d\n", *read_data);
usleep(10000);
*/
alt_flash_close_dev(flash_handle);
printf("close flash device...\n");

//写入SDRAM
p = (int*)( DDR2_SDRAM_BASE ); // DDR2_SDRAM_BASE 0x04000000 DDR2_SDRAM_SPAN
q=p;
*q++=*read_data++;
*q++=*read_data++;
*q++=*read_data++;
//从SDRAM中读出

A=*p++;
B=*p++;
x=*p;
y=A*x+B;
printf(" y= %d\n", y);
}
else
{
printf( "open flash device failed!!!\n");
}
return( 0 );
}