Random Number generator using 8051 Microcontroller

IC 74LS48:

The IC 74LS48 or 7448 is a simple BCD to 7 segment decoder which was used to reduce the usage of pins dedicated to the 7 segment display. It consists of 4 input pins namely 1,2,3,4 which is used to feed 4 bit data input to the IC. The fed 4 bit input binary data in turn decoded by the IC and output is obtained from the pins a, b ….. f  which is connected to the corresponding pins of the 7 segment display. This will display the correct digit in the 7 segment display.

DESIGN:

In the above design i have used two 7448 IC to interface two 7 segments in a single port, this will save the pin usage from the microcontroller. You can also go for direct interfacing of  a 7 segment with a dedicated port if you don’t have 7448 IC in your possession. 

Interrupt 0 feature of the Microcontroller was used here, therefore a simple push button was interfaced with the pin INT0 pin of the 8051 controller. Reset button was used with the pin 9 to reset the operation and start running the program from the beginning.

NUMBER GENERATION PROCESS:

• Initially the number keeps running from 0 to 99 in the display at high speed in a loop, so it will barely visible to human eye. 
• Pressing the interrupt button fetches the random number and displays it in the 7 segment display.
• The the reset button should be pressed to initialize the program and counting again.

 CODE: 

#include<regx51.h>
int a,b;
void delay();
void main()
{
  IE=0x81;                   //External interrupt activation
  while(1)
  {
  for(a=0;a<=9;a++)     //Number generation
  {
   for(b=0;b<=9;b++)
    {
      P2=a|b<<4;
      delay();
    }
   }
  }
}
void delay()
{
  int i;
  for(i=0;i<=400;i++);
}

void extr0(void) interrupt 0     //Subroutine EX0 with interrupt number '0'
{
    P2=a|b<<4; 
    while(1);
}

• Resistors for 7 segment are omitted for the simplicity of the schematic diagram, hook up a 470 ohm resistor to each pins connecting from 74LS48 to 7 segment pins.