am335x 串口启动 点灯实验

am335x，arm cortex-a8
led 位于 gpio0_3
复位默认如下

GPIO_OE Register (offset = 134h) [reset = FFFFFFFFh]

GPIO_DATAOUT Register (offset = 13Ch) [reset = 0h]

汇编代码如下：

.section .text

start:

ldr r0, =0x44E07134
ldr r1, [r0, #0]
and r1, r1, #0xfffffff7
str r1, [r0, #0]
ldr r0, =0x44E0713c
ldr r1, [r0, #0]
orr r1, r1, #0x1000
str r1, [r0, #0]
b start

.end

arm-eabi-as test.asm
arm-eabi-objcopy -O binary a.o boot

使用x-modem发送给开发板，但是led并没有变化
有大神能指出哪里错了吗

https://www.csdn.net/gather_15/MtjacgzsMTQzODAtZG93bmxvYWQO0O0O.html