为什么1602上不显示A

#include<reg52.h>
sbit rs=P1^5;
sbit rw=P1^6;
sbit lcden=P1^7;
void delay(unsigned int x)//延时
{
   int a;
    char b;
    for(a=0;a<x;a++);
     for(b=0;b<124;b++);
}
void write_com( unsigned char com) // 写命令
{
rs=0;
rw=0;
lcden=0;
delay(5);
P0=com;
lcden=1;
delay(5);
lcden=0;
}
void write_data( unsigned char dat)//写数据
{
rs=1;
rw=0;
lcden=0;
delay(5) ;
P0=dat;
lcden=1;
delay(5);
lcden=0;
}
void init()//初始化
{
write_com(0x38);
write_com(0x08);
write_com(0x01);
write_com(0x06);
write_com(0x0f);
}
void main()
{
init();
  while(1){
write_data('A'); }
}