Microcontroller learning---MC-S51 microcontroller introduction

The MCS-51 single-chip microcomputer was launched by the American INTE company in 1980. Compared with the MCS-48 single-chip microcomputer, it has a more advanced structure and stronger functions. It adds more circuit units and instructions on the original basis, with the number of instructions reaching 111. The MCS-51 single-chip microcomputer can be regarded as a very successful product. Until now, the MCS-51 series or its compatible single-chip microcomputers are still the mainstream products used. The training materials of various universities and professional schools still use the MCS-51 single-chip microcomputer as a representative for theoretical basic learning. We also use this representative model for systematic explanation.
   
The MCS-51 series of microcontrollers mainly include general products such as 8031, 8051 and 8751. Its main functions are as follows:

   ·8-bit CPU
   ·4kbytes program memory (ROM)
   ·128bytes data memory (RAM)
   ·32 I/O lines
   ·111 instructions, most of which are single-byte instructions
   ·21 special registers
   ·2 programmable timers/counters
   ·5 interrupt sources, 2 priorities
   ·One full-duplex serial communication port
   ·External data memory addressing space is 64kB
   ·External program memory addressing space is 64kB
   ·Logic operation bit addressing function
   ·Dual in-line 40PinDIP package
   ·Single +5V power supply

 

MCS-51 is a "famous machine" with its typical structure and perfect centralized management of bus-specific registers, numerous logic bit operation functions and rich control-oriented instruction system, which laid the foundation for the development of other single-chip microcomputers in the future. Because of its superior performance and perfect structure, many manufacturers later adopted or referred to its architecture. Many world-class electrical companies enriched and developed MCS-51 single-chip microcomputers. Famous semiconductor companies such as PHILIPS, Dallas, and ATMEL have launched single-chip microcomputer products compatible with MCS-51. Even Taiwan's WINBOND company has developed single-chip microcomputer varieties compatible with C51 (people are accustomed to abbreviating MCS-51 as C51. If there is no special statement, the two refer to the MCS-51 series of single-chip microcomputers).

 

In recent years, C51 has achieved rapid development. INTEL, the birthplace of C51, was too busy developing PCs and high-end microprocessors to continue developing its own single-chip microcomputers, so other manufacturers developed it, the most typical of which are PHILIPS and ATML. PHILIPS mainly improved its performance, and developed high-speed I/O ports, A/D converters, PWM (pulse width modulation), WDT and other enhanced functions on the original basis, and improved it with low voltage, micro power consumption, extended serial bus (I2C) and control network bus (CAN) and other functions.

 

PHILIPS has made a lot of contributions to the development of C51's low power consumption, high speed and enhanced functions. It was mainly responsible for the development of C51 microcontrollers. Their 83Cxx and 87Cxx series omitted the parallel expansion bus and were suitable for economical microcontrollers for household appliances.
   
The AT89Cxx series of microcontrollers compatible with C51 launched by ATMEL perfectly combined Flash (non-volatile flash technology) EEPROM with the 80C51 core, and still adopted the overall structure and instruction system of C51. The rewritable program memory of Flash can effectively reduce the development cost and enable the microcontroller to be reused many times.
   
Siemens also used the core of C51 and launched the C500 series of microcontrollers one after another. Under the premise of maintaining compatibility with C51 instructions, the performance of its products has been further improved, especially in anti-interference performance, electromagnetic compatibility and communication control bus functions. Its products are often used in places with harsh working environments. It is also suitable for the fields of communication and household appliance control.
   
Taiwan's WINBOND company has also developed a series of C51-compatible single-chip microcomputers. Its products usually have rich functional features, and with their high quality and low price, they also have a certain share in the market.
   
The following table shows the main classification and functional features of the 80C51 series single-chip microcomputers:

 

Series    Typical Chip I/O Port Timer/Counter Interrupt Source Serial Communication Port On-Chip RAM   On-Chip ROM     Description
       80C31   4x8-bit   2x16-bit     5     1        128 bytes     None   
       80C51   4x8-bit   2x16-bit     5  1  128 bytes  4kB Mask ROM  51 Series  87C51  4x8-bit  2x16-bit  5     1  128 bytes  4kB EPROM  89C51  4x8-bit  2x16-bit  5  1  128 bytes  4kBE EPROM          
                 
                       

 

      80C32   4x8 bit   2x16 bit     6      1        256 bytes    No   
       80C51   4x8 bit   2x16 bit     6      1        256 bytes    8kB Mask ROM   
52 series  87C52   4x8 bit   2x16  bit    6      1        256 bytes    4kBEPROM   
      89C52   4x8 bit   2x16 bit     6      1        256 bytes    4kBEEPROM  

 

8051 is the representative product of the MCS-51 series of microcontrollers. It integrates a powerful central processing unit, including a hardware multiplier and divider, 21 dedicated control registers, 4kB of program memory, 128 bytes of data memory, 4 groups of 8-bit parallel ports, two 16-bit programmable timers/counters, a full-duplex serial port and a Boolean processor.

 

MCS-51 has a relatively large addressing space, with an address line width of 16, that is, the addressing range of the external data memory and program memory is 216=64kB, which is relatively large for single-chip control, and it also has the ability to access the I/O port. In addition, MCS-51 adopts a modular structure, and it is easy to add or delete a module to produce a new product with compatible pins and instructions. This makes it easy to form a series of products.

 

Since MCS-51 integrates an almost perfect 8-bit central processing unit with powerful processing capabilities, the central processing unit integrates convenient and flexible special registers, hardware addition, subtraction, multiplication, division and Boolean processors as well as various logical operations and transfer instructions, which provides great convenience for applications.

 

The instruction system of MCS-51 is almost perfect. It includes comprehensive data transmission instructions, perfect arithmetic and logic operation instructions, convenient logic operation and control instructions, and is quite flexible and convenient for programming. The
   
operating frequency of MCS-51 microcontroller is 2-12MHz. When the oscillation frequency is 12MHz, one machine cycle is 1us, which is relatively fast.

 

8051 integrates a complete range of interrupt sources, and users can easily control and use its functions, which expands its application range. It can be said that it can meet most application scenarios.

 

MCS-51 integrates the main components of the microcomputer on a single chip, which greatly shortens the data transmission distance, improves reliability, and runs faster. As it is a chip-based microcomputer, the layout and structure of each functional component in the chip are optimized, the anti-interference ability is enhanced, and the operation is relatively stable. Therefore, in industrial measurement and control systems, the use of single-chip microcomputers is the most ideal choice. Single-chip microcomputers are typical embedded systems, so they are the best devices for low-end control systems.

 

The development environment requirements of MCS-51 are relatively low, and the software resources are very rich. Books introducing its functions and features and development software are available everywhere. All you need is a PC (personal computer - there are basically no requirements for the computer configuration) and an emulator programmer to develop products. Early development software mostly used DOS versions. With the popularization of Windows software, almost all of them now use Windows versions, and there are many types of software. Among the many types of single-chip microcomputers, C51 has the richest environmental resources, which brings great convenience to C51 users.