SCM was born in 1971. It has experienced three stages: SCM, MCU and SOC. The early SCM microcontrollers were 8-bit or 4-bit. Among them, the most successful is Intel 8031, and then MCS51 series MCU system was developed on 8031. The single chip microcomputer system based on this system is still widely used until now. With the improvement of requirements in the field of industrial control, 16 bit single chip microcomputer began to appear, but it has not been widely used because of its poor cost performance. After the 1990s, with the great development of consumer electronic products, the technology of single chip microcomputer has been greatly improved. With the wide application of Intel i960 series, especially the later arm series, 32-bit MCU quickly replaced the high-end position of 16 bit MCU and entered the mainstream market.