Design a sequential logic circuit that will act as a decimal countdown counter using a number of 7-segment displays beside some input device for initializing the count of each counter. The user sets up the decimal count for each digit manually by pressing the one of the setup buttons (number of buttons is a design task). The counter starts counting down in decimal until it reaches zero. When done this action opens lock (simulated by a LED).

Design Requirements

 The design should work as well as a Lock Opener. Therefore, when the user enters a secret digit decimal key the lock opens (the number of keys left as a design task) This will utilized by the load action to a register

 The circuit must have some input control line X1, X2, etc., similar to the number of counters, acting as switches that triggers the counters for loading initial digits. Therefore, when a switch in pressed, corresponding 4-bit counter will add up by one until it reaches the required digit, then we may proceed to the next counter.

 For the Lock Opener, the PIN is saved as a hardwired pattern for a comparator component to work on (see EXOR gates and how it works as a comparator) that compares the 4 4-bit key with the 4 counter outputs.

 The 7- segment display (common enable) is directly linked to the counters and it always shows what the counters is currently holding.

Simulation Software

Use it to embed all the project circuit.

oThe student is required to use IO capability of the package to simulate switches opening and closing operations (needed to increment or decrement all counters). Also LEDs should be connected to states storage cells.