mini2440的nandflash裸机代码

根据韦东山的代码改的程序，，不知道哪里有问题，led不亮，只改了nand.c程序，其他的和韦东山的一样，请各位帮忙看看。
*************************************nand.c***************************************************
#define NFCONF (*(volatile unsigned long *)0x4e000000)

#define NFCONT (*(volatile unsigned long *)0x4e000004)

#define NFCMD (*(volatile unsigned long *)0x4e000008)

#define NFADDR (*(volatile unsigned long *)0x4e00000C)

#define NFDATA (*(volatile unsigned long *)0x4e000010)

#define NFSTAT (*(volatile unsigned long *)0x4e000020)

#define NFCONF (*(volatile unsigned long *)0x4e000000)



#define NAND_SECTOR_SIZE_LP 2048

#define NAND_BLOCK_MASK_LP (NAND_SECTOR_SIZE_LP-1)



#define TACLS 0

#define TWRPH0 3

#define TWRPH1 0



#define send_cmd(cmd) {NFCMD=(cmd);}

#define send_addr(addr) {NFADDR=(addr);}

#define send_data(date) {NFDATA=(date);}

#define read_byte() NFDATA

#define enable() {NFCONT&=~(1<<1);}

#define disable() {NFCONT|=(1<<1);}

#define enable_rb() {NFSTAT|=(1<<2);}

#define check_busy() {while(!(NFSTAT&(1<<2)));}

#define waitrb() {while(!(NFSTAT&(1<<2)));}



void nand_read(unsigned char *buf,unsigned long start_addr,int size);



static void nand_reset()

{

        enable();

        enable_rb();

        send_cmd(0xff);

        check_busy();

        disable();      

}



void nand_init()

{

        NFCONF=(TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4)/*|(3<<2)|(1<<1)*/;

        NFCONT=(1<<4)|(1<<1)|(1<<0);

        NFSTAT=0;

        nand_reset();

}



static void write_addr(unsigned int addr)

{

        int i;

        int col,page;

        col=addr&NAND_BLOCK_MASK_LP;

        page=addr/NAND_SECTOR_SIZE_LP;

        send_addr(col&0xff);
        for(i=0;i<10;i++);

        send_addr((col>>8)&0x0f);
        for(i=0;i<10;i++);

        send_addr(page&0xff);
        for(i=0;i<10;i++);

        send_addr((page>>8)&0xff);
        for(i=0;i<10;i++);

        send_addr((page>>16)&0x03);
        for(i=0;i<10;i++);      

}



void nand_read(unsigned char *buf,unsigned long start_addr,int size)

{

        int i,j;

        enable();

        for(i=start_addr;i<(start_addr+size);)

        {

                send_cmd(0x00);

                write_addr(i);

                send_cmd(0x30);

                check_busy();

                for(j=0;j<NAND_SECTOR_SIZE_LP;i++,j++)

                {

                        *buf=read_byte();

                        buf++;

                }      

        }      

        disable();

}