The development of historical single chip microcomputer has experienced 4-bit, 8-bit, 16 bit and 32-bit stages. Due to its strong function, 8-bit single chip microcomputer is widely used in various fields such as industrial control, intelligent interface, instruments and meters. 8-bit single chip microcomputer still occupies the mainstream position in medium and small-scale applications, represents the development direction of single chip microcomputer and plays an increasingly important role in the field of single chip microcomputer application. In the early 1980s, Intel introduced an 8-bit MCS-51 series single chip microcomputer. The logic unit of MCS-51 single chip microcomputer, including an 8-bit CPU and on-chip oscillator, 80514b mask ROM, 87514keprom, 8031 no ROM, special function register sfr128bram, timer / counter t0 and T1, parallel I / O interfaces: P0, P1, P2, P3; Serial interface: TXD, RXD; Interrupt system: INT0, INT1. Basic functions: 1.8-bit data bus, 16 bit address bus CPU;

2. Boolean processing capability and bit processing capability;

3. Harvard structure is adopted, and the address space of program memory and data memory are independent, which is convenient for program design;

4. 64KB program memory and 64KB data memory with the same address;

5.0-8kb on-chip program memory (8031 no, 8051 4KB, 8052 8KB, 89c55 20KB);

6.128 byte on-chip data memory (there are 256 bytes in 8051);

7.32 bidirectional and bit addressable I / O lines;

8. Two 16 bit timing / counters (3 for 8052);

9. A full duplex serial I / O interface;

10. Interrupt structure of multiple interrupt sources. The single chip microcomputer scheme has two interrupt priorities;

11. On chip clock oscillator.