Microcontroller unit (MCU) can be classified from different aspects: according to the width of data bus, it can be divided into 8-bit, 16 bit and 32-bit computers; According to the memory structure, it can be divided into Harvard structure and von Neumann structure; According to the category of embedded program memory, it can be divided into OTP, mask, eprom/eeprom and flash memory; According to the instruction structure, it can be divided into CISC (complex instruction set computer) and RISC (reduced instruction set computer) microcontrollers. Microcontrollers based on RISC architecture include microchip's pic series 8-bit microcontrollers. Among the 16 bit RISC microcontrollers, MAXQ series microcontrollers launched by Maxim company have become an ideal choice for many high-precision mixed signal processing, portable systems and battery powered systems because of their high performance, low power consumption and excellent code execution efficiency.