Principle and application of single chip microcomputer - principle of parallel IO port

List of articles

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Tips ： The following is the main body of this article , The following cases can be used for reference

One 、 MCU parallel IO How mouth works

P1 mouth ：

P1 Of IO The parallel internal structure is composed of D Trigger and latch
Internal bus input 0, Trigger output Q’ by 1,MOS The pipe is open , Output end output 0;
Internal input 1, Trigger output Q’ by 0,MOS Tube stop , Output end output 1;
that PI As the input port, the latch is used to read data , To read data, you must first keep MOS Tube stop , be Q’ Output 0, therefore P1 Before reading external data through the port, you should first look like P1 output 1.
P3 mouth ：

P2 mouth ：

Control terminal （0）,P2 The working principle of the port is the same as P1 mouth ;
The control port is （1）,P2 Port output address bus

P0 mouth ：

P0 The port requires the user to connect an external pull-up resistor to work properly .
Control terminal （0）,P0 As ordinary IO mouth , The working principle is the same as P1 mouth
Control terminal （1）,P0 As the address / Data multiplexing bus

Two 、51 Working cycle and timing of single chip microcomputer

1. Clock circuit

Passive quartz crystal oscillator ：

Active crystal oscillator ： Relative to passive , More stable and reliable clock signal

2. Reset mode

The reset methods are ： Power on automatic reset and manual button reset

3. Machine cycle and instruction cycle

Machine cycle ： The basic unit of single chip microcomputer operation , A machine cycle consists of 12 Clock cycles .

Instruction cycle ： The time from the computer fetching the instruction to the execution of the instruction is Instruction cycle

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3、 ... and 、C51 New variable type

special function register sfr Definition
C51 Define the special function registers and special bits commonly used by MCU , Put it in “reg51.h” Header file .
Bit variable

When defining a variable, it indicates the data type and memory type of the variable

Four 、 Definition of function

Added the definition of interrupt function
C51 When defining an interrupt function, the suffix must be interrupt m
m The value range is as follows ：