ARM·系統(tǒng)時鐘（MPLL,UPLL）

【程序設計】

clock_int函數用于設置MPLL，2440A的輸入時鐘頻率Fin為12Mhz，將FCLK，HCLK，PCLK分別設為200MHz，100MHz，50MHz

思路：分頻就是2步

1）：設置MPLL（把12MHz倍頻）

2）：設置CLKDIVN（把MPLL分頻）

【代碼詳解】

#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, 0"

"orr r1, r1, #0xc0000000"

"mcr p15, 0, r1, c1, c0, 0"

);

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++;

}

}