OK6410裸机学习之时钟设置-C语言

start.S源码：

.globl _start

_start:

// 硬件相关的设置 

    // Peri port setup 

    ldr r0, =0x70000000

    orr r0, r0, #0x13

    mcr p15,0,r0,c15,c2,4       @ 256M(0x70000000-0x7fffffff)

// 关看门狗 

    // 往WTCON(0x7E004000)写0 

    ldr r0, =0x7E004000

    mov r1, #0

    str r1, [r0]

    // 设置栈 

    ldr sp, =8*1024

    // 设置时钟 

    bl clock_init

    bl main

halt:

    b halt    

===================================================================

clock.c源码：

#define APLL_LOCK (*((volatile unsigned long *)0x7E00F000))

#define MPLL_LOCK (*((volatile unsigned long *)0x7E00F004))

#define EPLL_LOCK (*((volatile unsigned long *)0x7E00F008))

#define OTHERS    (*((volatile unsigned long *)0x7e00f900))

#define CLK_DIV0  (*((volatile unsigned long *)0x7E00F020))

#define ARM_RATIO    0     // ARMCLK = DOUTAPLL / (ARM_RATIO + 1)    

#define HCLKX2_RATIO 4   // HCLKX2 = HCLKX2IN / (HCLKX2_RATIO + 1) = 100MHz 

#define HCLK_RATIO   0     // HCLK = HCLKX2 / (HCLK_RATIO + 1)   = 100MHz       

#define PCLK_RATIO   1     // PCLK   = HCLKX2 / (PCLK_RATIO + 1) = 50MHz    

#define MPLL_RATIO   0    // DOUTMPLL = MOUTMPLL / (MPLL_RATIO + 1)     

#define APLL_CON  (*((volatile unsigned long *)0x7E00F00C))

#define APLL_CON_VAL  ((1<<31) | (250 << 16) | (3 << 8) | (1))

#define MPLL_CON  (*((volatile unsigned long *)0x7E00F010))

#define MPLL_CON_VAL  ((1<<31) | (250 << 16) | (3 << 8) | (1))

#define CLK_SRC   (*((volatile unsigned long *)0x7E00F01C))

//MDIV=250 对应： ARMCLK = 500MHz, HCLK = 100MHz, PCLK = 50MHZ 

//MDIV=266 对应： ARMCLK = 532MHz, HCLK = 133MHz, PCLK = 66.5MHZ 

void clock_init(void)

{

    APLL_LOCK = 0xffff;

    MPLL_LOCK = 0xffff;

    EPLL_LOCK = 0xffff;

    // set async mode 当CPU时钟 != HCLK时，要设为异步模式 

    OTHERS &= ~0xc0;

    while ((OTHERS & 0xf00) != 0);

    CLK_DIV0 = (ARM_RATIO) | (MPLL_RATIO << 4) | (HCLK_RATIO << 8) | (HCLKX2_RATIO << 9) | (PCLK_RATIO << 12);

    APLL_CON = APLL_CON_VAL;    // 500MHz 

    MPLL_CON = MPLL_CON_VAL;  // 500MHz 

    CLK_SRC = 0x03;

}

====================================================================

led.c源码：

void delay()

{

    volatile int i = 0x10000;

    while (i--);

}

int main()

{

    int i = 0;

    volatile unsigned long *gpmcon = (volatile unsigned long *)0x7F008820;

    volatile unsigned long *gpmdat = (volatile unsigned long *)0x7F008824;

    // gpm0,1,2,3设为输出引脚 

    *gpmcon = 0x1111;

    while (1)

    {

        *gpmdat = i;

        i++;

        if (i == 16)

            i = 0;

        delay();

    }

    return 0;

}

====================================================================

Makefile：

led.bin: start.o clock.o led.o

    arm-linux-ld -Ttext 0 -o led.elf start.o clock.o led.o

    arm-linux-objcopy -O binary led.elf led.bin

    arm-linux-objdump -D led.elf > led.dis

%.o : %.S

    arm-linux-gcc -o $@ $< -c

%.o : %.c

    arm-linux-gcc -o $@ $< -c

clean:

    rm *.o led.elf led.bin led.dis