51 single chip microcomputer, light up LED light and flash

 1. The difference between the keywords sfr and sbit

        sfr is the byte address of the register, and sbit is the bit address of the bit-addressable register.

        For example: sfr P1 = 0x90;

        sbit A = P1^0 sbit B = P1^1;

2. The microcontroller pins are: power pin, crystal pin, reset pin, download pin, GPIO pin

The crystal pin is mainly used to provide an external clock to drive instruction execution. The GPIO pins include four ports: P0, P1, P2, and P3.

3. Light up an LED

From the circuit diagram, we can know that the LED is the P2 port. If we give the P2.0 pin a low voltage, that is, 0V, the first one will light up. The procedure is as follows       

#include"reg52.h" //reference header file

int main()

{

    P2 = 0xFE; //1111 1110 represents the output voltage status of P2.0----P2.7 pins

    while(1)

    {

    }

     return 0;

}

If I output low voltage to all pins of port P2, P2=0x00, then all LEDs will light up, as shown below

4. LED light flashes

The LED light is controlled to flash by outputting high and low levels, but due to the afterglow effect of the human eye, the flashing cannot be seen, so a delay is needed to achieve the effect. The program is as follows

#include"reg52.h" //reference header file

void Delay(int time)

{

    while(time--) //while loop takes 10us

    {

    }

}

int main()

{

    while(1)

    {

        P2 = 0xFF;

        Delay(50000); //Delay about 450ms

        P2 = 0xFE;

        Delay(50000); //Delay about 450ms 

    }

     return 0;

}

The experimental phenomena are as follows