start.S源码:
.globl _start
.globl delay //用globl声明,外部函数就可以调用delay函数
_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
mov r0, #9
bl xxxxx
halt:
b halt
delay:
delay_loop:
cmp r0, #0
sub r0, r0, #1
bne delay_loop
mov pc, lr
====================================================================
led.c源码:
void delay(int count); //声明
int xxxxx(int start)
{
int i = start;
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 = (*gpmcon & ~0xffff) | 0x1111;
while (1)
{
*gpmdat = (*gpmdat & ~0xf) | i;
i++;
if (i == 16)
i = 0;
delay(0x10000);
}
return 0;
}
====================================================================
Makefile:
led.bin: start.o led.o
arm-linux-ld -Ttext 0 -o led.elf start.o led.o
arm-linux-objcopy -O binary led.elf led.bin
arm-linux-objdump -D led.elf > led.dis
start.o : start.S
arm-linux-gcc -o start.o start.S -c -O2
led.o : led.c
arm-linux-gcc -o led.o led.c -c -O2
clean:
rm *.o led.elf led.bin led.dis
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