ARM development (1) Preparatory knowledge – semiconductor devices, analog and digital parts, computer composition and principles

A preliminary knowledge point

1. Semiconductor devices

(1) Switching characteristics of semiconductor devices

Logic 0 and 1: represented by high and low levels in digital electronic circuits.

The basic method of obtaining high and low levels: using the two working states of on and off (i.e. on and off) of semiconductor switching elements

(2) Diode

Diode symbol:


After encapsulating a PN junction and leading out the electrode, a diode is formed. When a forward voltage is applied to the diode, a diffusion current is generated, and the current is exponentially related to the voltage; when a reverse voltage is applied, an escape current is generated, and its value is very small;Demonstrates single conductivity

Special diodes also have unidirectional conductivity. The breakdown characteristics of the PN junction can be used to make a zener diode, the luminescent material can be used to make a light-emitting diode, and the photosensitivity of the PN junction can be used to make a photodiode.

(3) Transistor

Difference: The emitter points to the base, which is PNP

The base points to the emitter, which is NPN.

Transistor symbol:


        Transistors have the function of current amplification, is the core component of electronic circuits.

There are two types of transistors (hereinafter referred to as transistors) based on materials: germanium tubes and silicon tubes. The essence is that the triode can control a large change in the collector current with a small change in the base current. This is the most basic and important characteristic of the triode. According to the potential of each electrode when the triode is working, the working status of the triode can be judged.

(4) MOS tube (field effect tube)

MOS tube symbol:


Field effect transistors are divided into two types: junction type and insulated gate type. Each type is divided into N channel and P channel. MOS tubes in the same channel are divided into two forms: enhancement type and depletion type.


MOS tubes are mainly for accessoriesProvide stable voltage, so it is generally used near the CPU, AGP slot and memory slot. Among them, a set of MOS tubes is arranged near the CPU and AGP slot, while the memory slots share a set of MOS tubes. MOS tubes generally appear in a group of two on the motherboard.
1. When the MOS works in the conduction area or cut-off area, it canwhen switchuse. An external PWM signal canUsed for voltage regulation and motor speed regulationetc.
2. Combining several MOS tubes can achieveone way traffic(similar to the one-way conduction of a diode), its advantages over diodes are small voltage drop, low power consumption, and large conduction current. The advantages are more obvious in the case of low voltage and high current;
3. When working in the variable resistance area, it canWhen a resistorGenerally, the resistors in integrated chips use this method. The advantage is that it is easy to produce and small in size.
4. Working in the variable resistance area can also play a roleenlargeIts function is similar to that of a triode amplifier circuit.


Field effect transistors are voltage-controlled semiconductor devices. It has the advantages of high input resistance, low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown phenomenon, and wide safe working area.

2. Analog digital part

(1). “AND” operation and “AND” gate

(2). “OR” operation and “OR” gate

(3). “NOT” operation and “NOT” gate

3. Principles of computer composition


The physical part of the computer can realize the most basic operating behavior of the computer.

Computer system hardware components

1) Input device

The task of the input device is to send the programs and raw data compiled by people to the computer, and convert them into information that can be recognized and accepted by the computer. Commonly used ones include keyboard, mouse, scanner, etc.

2) Output device

The task of the output device is to send the computer’s processing results out of the computer in a form acceptable to humans or other devices. Commonly used ones include monitors, printers, plotters, etc.

3) Memory

Memory is a component used to store programs and data. It is a memory device and the basis for computers to achieve “stored program control”.

Tertiary storage system


-1. Cache

The CPU can directly access it and is used to store the active part of the program currently being executed in order to quickly provide instructions and data to the CPU.

-2.Main memory

It can be directly accessed by the CPU and is used to store the programs and data currently being executed.

-3.Auxiliary storage

It is set outside the host and cannot be directly accessed by the CPU. It is used to store programs and data that are not temporarily involved in running. They are transferred to the main memory when needed.

4) Memory hierarchy


5) Calculator

The arithmetic unit is a component that processes and performs operations on information. The commonly performed operations are arithmetic operations and logical operations. Therefore, the core technology of the arithmetic unit is the arithmetic and logical operation unit ALU.

There are several registers in the operator (such as accumulation register, temporary register, etc.)



6) Controller

The controller is the command center of the entire computer

The controller mainly includes timing control signal forming components and some special registers



7) Computer bus structure

The major basic components are connected in a certain way to form the computer hardware system.

At present, the major basic components of many computers are connected by buses.

The bus is a set of public information transmission lines that can serve multiple components. It can send and receive information from each component in a time-sharing manner.

1.Single bus structure



2.Multiple bus structure





A collection of programs that enable computers to implement various functions, including system software and application software.

Computer system = hardware system + software system

Hardware is the material basis of a computer system, and software is the soul of a computer system. Hardware and software complement each other and are inseparable good friends.

4. ARM system composition and principle

1. Instruction fetching stage

2.Decoding process


tips (the machine code is written randomly, this is an example)

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