写一个简单的BootLoader（二）——init.c分析笔记

/* NAND FLASH控制器 */
#define NFCONF (*((volatile unsigned long *)0x4E000000))
#define NFCONT (*((volatile unsigned long *)0x4E000004))
#define NFCMMD (*((volatile unsigned char *)0x4E000008))
#define NFADDR (*((volatile unsigned char *)0x4E00000C))
#define NFDATA (*((volatile unsigned char *)0x4E000010))
#define NFSTAT (*((volatile unsigned char *)0x4E000020))

/* GPIO */
#define GPHCON              (*(volatile unsigned long *)0x56000070)
#define GPHUP               (*(volatile unsigned long *)0x56000078)

/* UART registers*/
#define ULCON0              (*(volatile unsigned long *)0x50000000)
#define UCON0               (*(volatile unsigned long *)0x50000004)
#define UFCON0              (*(volatile unsigned long *)0x50000008)
#define UMCON0              (*(volatile unsigned long *)0x5000000c)
#define UTRSTAT0            (*(volatile unsigned long *)0x50000010)
#define UTXH0               (*(volatile unsigned char *)0x50000020)
#define URXH0               (*(volatile unsigned char *)0x50000024)
#define UBRDIV0             (*(volatile unsigned long *)0x50000028)

#define TXD0READY   (1<<2)

void nand_read(unsigned int addr, unsigned char *buf, unsigned int len);

int isBootFromNorFlash(void)
{
volatile int *p = (volatile int *)0;
int val;

val = *p;
*p = 0x12345678;
if (*p == 0x12345678)
{
/* 写成功, 是nand启动 */
*p = val;
return 0;
}
else
{
/* NOR不能像内存一样写 */
return 1;
}
}

void copy_code_to_sdram(unsigned char *src, unsigned char *dest, unsigned int len)
{
int i = 0;

/* 如果是NOR启动 */
if (isBootFromNorFlash())
{
while (i < len)
{
dest[i] = src[i];
i++;
}
}
else
{
//nand_init();
nand_read((unsigned int)src, dest, len);
}
}

void clear_bss(void)
{
extern int __bss_start, __bss_end;//这边的两个变量在链接脚本中
int *p = &__bss_start;

for (; p < &__bss_end; p++)
*p = 0;
}

void nand_init(void)
{
#define TACLS   0
#define TWRPH0  1 //这个要大于等于15ns,系统使用的HCLK是100MHz
#define TWRPH1  0
/* 设置时序 */
NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
/* 使能NAND Flash控制器, 初始化ECC, 禁止片选 */
NFCONT = (1<<4)|(1<<1)|(1<<0);
}

void nand_select(void)
{
NFCONT &= ~(1<<1);
}

void nand_deselect(void)
{
NFCONT |= (1<<1);
}

void nand_cmd(unsigned char cmd)
{
volatile int i;
NFCMMD = cmd;
for (i = 0; i < 10; i++);//经验之谈，发送之后需要等待，韦老师自己说的，调了很久才发现这个问题
}

void nand_addr(unsigned int addr)
{
unsigned int col  = addr % 2048;
unsigned int page = addr / 2048;
volatile int i;

NFADDR = col & 0xff;
for (i = 0; i < 10; i++);
NFADDR = (col >> 8) & 0xff;
for (i = 0; i < 10; i++);

NFADDR  = page & 0xff;
for (i = 0; i < 10; i++);
NFADDR  = (page >> 8) & 0xff;
for (i = 0; i < 10; i++);
NFADDR  = (page >> 16) & 0xff;
for (i = 0; i < 10; i++);
}

void nand_wait_ready(void)
{
while (!(NFSTAT & 1));
}

unsigned char nand_data(void)
{
return NFDATA;
}

void nand_read(unsigned int addr, unsigned char *buf, unsigned int len)
{
int col = addr % 2048;
int i = 0;

/* 1. 选中 */
nand_select();

while (i < len)
{
/* 2. 发出读命令00h */
nand_cmd(0x00);

/* 3. 发出地址(分5步发出) */
nand_addr(addr);

/* 4. 发出读命令30h */
nand_cmd(0x30);

/* 5. 判断状态 */
nand_wait_ready();

/* 6. 读数据 */
for (; (col < 2048) && (i < len); col++)
{
buf[i] = nand_data();
i++;
addr++;
}

col = 0;
}

/* 7. 取消选中 */
nand_deselect();
}

#define PCLK            50000000    // init.c中的clock_init函数设置PCLK为50MHz
#define UART_CLK        PCLK        //  UART0的时钟源设为PCLK
#define UART_BAUD_RATE  115200      // 波特率
#define UART_BRD        ((UART_CLK  / (UART_BAUD_RATE * 16)) - 1)

/*
* 初始化UART0
* 115200,8N1,无流控
*/
void uart0_init(void)
{
GPHCON  |= 0xa0;    // GPH2,GPH3用作TXD0,RXD0
GPHUP   = 0x0c;     // GPH2,GPH3内部上拉

ULCON0  = 0x03;     // 8N1(8个数据位，无较验，1个停止位)
UCON0   = 0x05;     // 查询方式，UART时钟源为PCLK
UFCON0  = 0x00;     // 不使用FIFO
UMCON0  = 0x00;     // 不使用流控
UBRDIV0 = UART_BRD; // 波特率为115200
}

/*
* 发送一个字符
*/
void putc(unsigned char c)
{
/* 等待，直到发送缓冲区中的数据已经全部发送出去 */
while (!(UTRSTAT0 & TXD0READY));

/* 向UTXH0寄存器中写入数据，UART即自动将它发送出去 */
UTXH0 = c;
}

void puts(char *str)
{
int i = 0;
while (str[i])
{
putc(str[i]);
i++;
}
}

void puthex(unsigned int val)
{
/* 0x1234abcd */
int i;
int j;

puts("0x");

for (i = 0; i < 8; i++)
{
j = (val >> ((7-i)*4)) & 0xf;
if ((j >= 0) && (j <= 9))
putc('0' + j);
else
putc('A' + j - 0xa);
}
}