说明：  12864串行输出控制，本来一个单片机控制12864需要20个管脚，现在通过SCK，SDA等几个串行线控制减少了单片机的管脚数量要求
(12864 Serial output control, originally a single-chip control 12864 20 pins now by SCK, SDA, and several serial line control to reduce the number of pins of a microcontroller requirements)