52 microcontroller IO port output lights up your LED

Special function register SFR declaration

If we want to use the IO port of the microcontroller, we must first define its address. We can find the address corresponding to the IO port from the chip data (you can also search directly online)

Microcontroller C language SFR statement:

sfr P0 = 0x80;

sfr P1 = 0x90;

sfr P2 = 0xA0;

sfr P3 = 0xB0; //Define P0~P3

After defining it, by controlling P0~P1, we can control their corresponding 8 IO ports at the same time. Of course, this time we only need to light up one or two LEDs and only need to use one or two IO ports, so we can use the following The method defines an IO port separately.

sbit LED0 = P1 ^ 0;

sbit LED1 = P1 ^ 1;

sbit LED2 = P1 ^ 2;

sbit LED3 = P1^3;

sbit LED4 = P1 ^ 4;

sbit LED5 = P1 ^ 5;

sbit LED6 = P1 ^ 6;

sbit LED7 = P1 ^ 7; // Define the 8 IO ports of P1 respectively

Note: The IO port must be defined in capital letters.

head File

Earlier we used sfr to define the IO port. It would be very troublesome if we had to enter sfr one by one every time to define it. At this time, we can use the header file method instead of the previous method. The header file of the 52 microcontroller C language is .

This header file contains most of the definitions, which is convenient and fast. So why do we still need to talk about the sfr statement? In fact, it is to better understand the core content of the header file.

Code reference

Assigning a value of 0 to led0 allows its corresponding IO port to send out a low-level signal, thereby lighting up the LED.

#include

//sfr P1 = 0x90; //Define P1 register address

sbit led0 = P1^0;//led0 1st led

sbit led7 = P1^7;//led7 8th led

void main()

{

// led0 = 0; //Low level lights up led0

// while(1);//Stop the program here (infinite loop)

while(1)

{

led0 = 0;

led7 = 0;

}

}

Below is the final result picture. In the black frame are the first and eighth LEDs we lit.

Reference content link: https://www.bilibili.com/video/BV1Kt411Q7aV?p=4.