说明：   比如第二行第一个字符的地址是40H，那么是否直接写入40H就可以将光标定位在第二行第一个字符的位置呢？这样不行，因为写入显示地址时要求最高位D7恒定为高电平1所以实际写入的数据应该是01000000B（40H)+10000000B(80H)=11000000B(C0H)
(For example, the second line of the first characters of the address is 40H, then 40H whether you can write directly to the cursor location in the second line the first character of the exact location? This can not work because of the requirements written into the show address highest D7 constant 1 for the high actual write data should be 01000000B (40H)+ 10000000B (80H) = 11000000B (C0H))