MCU hardware knowledge

Since the MCS-51 microcontroller is an enhanced product based on the MCS-48, it has a higher chip integration, much better performance, more hardware functions, and a wider variety of functional units than the latter.

I/O Ports

The number and types of I/O ports inside the MCS-51 chip are numerous and complete, especially it has a full-duplex serial port, which highlights the inherent characteristics of this single-chip microcomputer. The serial port is composed of two I/O port lines and has 4 working modes that can be selected through programming. The MCS-51 has 32 I/O port lines, while the MCS-48 has only 27.

CPU

The central processing unit of a single-chip microcomputer is the core component inside the single-chip microcomputer, which determines the main functional characteristics of the single-chip microcomputer. The central processing unit is mainly composed of arithmetic components and control components.

ALU Function

The ALU function of the MCS-51 single-chip microcomputer is very powerful. It can not only perform basic operations such as logical "AND", "OR", "XOR" loop, complement, and zero clearing on 8-bit variables, but also perform basic operations such as addition, subtraction, multiplication, and division.

Accumulator ACC

The accumulator ACC in the microcontroller computing unit is an 8-bit accumulator. Functionally, it is not special compared with the accumulator of a general microcomputer, but the carry flag CY of ACC is a one-bit accumulator for the Boolean processor to perform bit operations.

Control components

The control unit is the central nervous system of the microcontroller. It includes clock circuit, reset circuit, instruction register, decoder and information transmission unit. The control unit of the microcontroller uses the main oscillation frequency as the reference, sends out the timing signal of the CPU, decodes the instruction, and then sends out various control signals to complete a series of timing control micro-operations to control the operation of various parts of the microcontroller. Among them, some control signal lines can simplify the peripheral control logic of the application system.

CPU Timing

Each instruction executed by the microcontroller can be decomposed into several basic micro-operations. These micro-operations have a very strict sequence in time. This sequence is the CPU timing of the computer.