Circuit : Milardo de Guzman, Philippines 
Email : milardo_dg@yahoo.com
A few months ago Milardo starting to study the 8051 Microcontroller. From his research Miardo has designed a new circuit and called it "3-Digit Display Scoreboard with 4x4 Keypad Matrix".
NotesHere is how the circuit works!
This is a circuit for scoreboard! It combines keypad matrix and 3-digit display.
Port1 scan the keypad while the Port3 outputs the binary equivalent of keypad being pressed.Only a single digit is driven by microcontroller. By using latches, the output of 74LS48 can be shifted to the left. Then we will have 3-digit display. You can also add a display by connecting 74LS273 and seven segment display.
To reset the display: Press F three times
To reset microcontroller: Press Reset Switch
The 7 segment display uses series limiting resistors of 220 ohms. There are 21 resistors used across the 3-seven segment displays. These are not drawn on the schematic for clarity.
Source Code for the Microcontroller.
The source code for the 8051 microncontroller is available below as an hex file.
To program the microcontroller you need suitable development software.