在Demo文件夹中startup.s文件中加入点灯代码,代码如下:
GPKCON0 EQU 0x7F008800
GPKDAT EQU 0x7F008808
GPKPUD EQU 0x7F00880C
IMPORT _main ; C entrypoint for Steppingstone loader.
AREA |C$$code|, CODE, READONLY
global Start
Start
ldr r0, = GPKCON0
ldr r1, = GPKDAT
ldr r2, = GPKPUD
mov r0,#0x00110000
mov r1,#0x0000
mov r2,#0x00000000
b _main
DCB "ABCDabcd"
END
将bin通过DNW下载到0x50000000处,发现led3、led4灯并没有亮。可见PC并没有跑到运行到这块代码来。U-BOOT代码中是下载应用程序到0x50000000完后,跳到该地址处执行吗?