@ File：head.S
@ 功能：設置SDRAM，將程序復制到SDRAM，然后跳到SDRAM繼續(xù)執(zhí)行
@******************************************************************************

.extern main
.text
.global _start
_start:
Reset:
ldr sp, =4096 @ 設置棧指針，以下都是C函數(shù)，調用前需要設好棧
bl disable_watch_dog @ 關閉WATCHDOG，否則CPU會不斷重啟

bl clock_init @ 設置MPLL，改變FCLK、HCLK、PCLK

bl memsetup @ 設置存儲控制器以使用SDRAM
bl copy_steppingstone_to_sdram @ 復制代碼到SDRAM中
ldr pc, =on_sdram @ 跳到SDRAM中繼續(xù)執(zhí)行
on_sdram:
ldr sp, =0x34000000 @ 設置棧指針，
ldr lr, =halt_loop @ 設置返回地址
ldr pc, =main @ 調用main函數(shù)
halt_loop:
b halt_loop

#include "s3c24xx.h"

void disable_watch_dog(void);
void clock_init(void);
void memsetup(void);
void copy_steppingstone_to_sdram(void);

void disable_watch_dog(void)
{
WTCON = 0; // 關閉WATCHDOG很簡單，往這個寄存器寫0即可
}

#define S3C2410_MPLL_200MHZ ((0x5c<<12)|(0x04<<4)|(0x00))
#define S3C2440_MPLL_200MHZ ((0x5c<<12)|(0x01<<4)|(0x02))

void clock_init(void)
{
// LOCKTIME = 0x00ffffff; // 使用默認值即可
CLKDIVN = 0x03; // FCLK:HCLK:PCLK=1:2:4, HDIVN=1,PDIVN=1

__asm__(
"mrc p15, 0, r1, c1, c0, 0n"
"orr r1, r1, #0xc0000000n"
"mcr p15, 0, r1, c1, c0, 0n"
);

if ((GSTATUS1 == 0x32410000) || (GSTATUS1 == 0x32410002))
{
MPLLCON = S3C2410_MPLL_200MHZ;
}
else
{
MPLLCON = S3C2440_MPLL_200MHZ;
}
}

void memsetup(void)
{
volatile unsigned long *p = (volatile unsigned long *)MEM_CTL_BASE;

p[0] = 0x22011110; //BWSCON
p[1] = 0x00000700; //BANKCON0
p[2] = 0x00000700; //BANKCON1
p[3] = 0x00000700; //BANKCON2
p[4] = 0x00000700; //BANKCON3
p[5] = 0x00000700; //BANKCON4
p[6] = 0x00000700; //BANKCON5
p[7] = 0x00018005; //BANKCON6
p[8] = 0x00018005; //BANKCON7


p[9] = 0x008C04F4;
p[10] = 0x000000B1; //BANKSIZE
p[11] = 0x00000030; //MRSRB6
p[12] = 0x00000030; //MRSRB7
}

void copy_steppingstone_to_sdram(void)
{
unsigned int *pdwSrc = (unsigned int *)0;
unsigned int *pdwDest = (unsigned int *)0x30000000;

while (pdwSrc < (unsigned int *)4096)
{
*pdwDest = *pdwSrc;
pdwDest++;
pdwSrc++;
}
}

"serial.h"

void uart0_init(void);
void putc(unsigned char c);
unsigned char getc(void);
int isDigit(unsigned char c);
int isLetter(unsigned char c);

#include "serial.h"

int main()
{
unsigned char c;
uart0_init(); // 波特率115200，8N1(8個數(shù)據(jù)位，無校驗位，1個停止位)

while(1)
{
// 從串口接收數(shù)據(jù)后，判斷其是否數(shù)字或子母，若是則加1后輸出
c = getc();
if (isDigit(c) || isLetter(c))
putc(c+1);
}

return 0;
}

#include "s3c24xx.h"
#include "serial.h"

#define TXD0READY (1<<2)
#define RXD0READY (1)

#define PCLK 50000000 // init.c中的clock_init函數(shù)設置PCLK為50MHz
#define UART_CLK PCLK // UART0的時鐘源設為PCLK
#define UART_BAUD_RATE 115200 // 波特率
#define UART_BRD ((UART_CLK / (UART_BAUD_RATE * 16)) - 1)

void uart0_init(void)
{
GPHCON |= 0xa0; // GPH2,GPH3用作TXD0,RXD0
GPHUP = 0x0c; // GPH2,GPH3內部上拉

ULCON0 = 0x03; // 8N1(8個數(shù)據(jù)位，無較驗，1個停止位)
UCON0 = 0x05; // 查詢方式，UART時鐘源為PCLK
UFCON0 = 0x00; // 不使用FIFO
UMCON0 = 0x00; // 不使用流控
UBRDIV0 = UART_BRD; // 波特率為115200
}

void putc(unsigned char c)
{

while (!(UTRSTAT0 & TXD0READY));


UTXH0 = c;
}

unsigned char getc(void)
{

while (!(UTRSTAT0 & RXD0READY));


return URXH0;
}

int isDigit(unsigned char c)
{
if (c >= 0 && c <= 9)
return 1;
else
return 0;
}

int isLetter(unsigned char c)
{
if (c >= a && c <= z)
return 1;
else if (c >= A && c <= Z)
return 1;
else
return 0;
}