Single chip microcomputer (AT89C51) peripheral I/O input and output experiment

Question Analysis

The main purpose is to connect 8 switches to the extended input port and 8 LEDs to the extended output port. How to control the display of 8 LEDs corresponding to 8 switches?

Other external chips are needed in the experiment

method one

Use 74LS373 and 74LS245 as external chips to complete the experiment

Experimental Circuit Diagram

Experiment Code

#include 

#include //define absolute address access

#define  uchar  unsigned  char

void delay(unsigned int n)

{

unsigned int i,j;

for(i=0;i   for(j=249;j>0;j--)

  ;

}

flying i;

void main(void)

{

    while(1)

{

i=XBYTE[0x7fff]; //Enter the switch information of the input port into i

delay(1); //delay program

XBYTE[0x7fff]= i; //Transfer the input switch information to the output address

}

}

The experimental code is not difficult to understand. It is to assign the button information of the input port (address 0x7fff) to i, and then transfer the data of the input port to the output port. The input port is connected to the button, and the output port is connected to the LED light. It is the same as the circuit diagram above.

Experimental Results

The LED light turns on and off corresponding to each button pressed.

Method Two

Use 8255 and 74LS373 as external chips to complete the experiment

Experimental Circuit Diagram

Experiment Code

#include 

#include     

#define  uchar  unsigned  char

flying i;

void delay(unsigned int n)

{

unsigned int i,j;

for(i=0;i   for(j=249;j>0;j--)

  ;

}

void  main (void) 

{ 

   while(1)

  {

   i= 0x90; //optional

  XBYTE[0xff7fc]= i; //optional

  i=XBYTE[0xff7c]; //Same as the above program

  delay(1); //Same as above program

  XBYTE[0xff7d]= i; //Same as the above program

  }

}

Experimental Results

The LED light turns on and off corresponding to each button pressed.

Summarize

The results of the I/O input and output experiment of the microcontroller (AT89C51) peripherals are relatively simple and clear, but it is mainly necessary to understand the experimental principles.