Microsoft Word - Digital Logic Design v_4_6a

 Design a 4-botton lock (red, blue, green and black) using T flip flop. The lock will open only when
Red, Green,Black and Red buttons are pressed in sequence.

Note: Assigning 2-bit value to each button will reduce the complexity of design.

Solution:

Step 1 – State Diagram Describing the system

Step 2 - 4 possible state  2 Flip Flops required

Use D flip flop since not specified.

Reset (^) R
RGB (^) RG
Note:
All input not shown will move the FSM to Reset State.
Red
Green
Black
Red
Key Code
k1 k0 Colo r
0 0 Red
0 1 Blue
1 0 Green
1 1 Black
Lock Controller
System Diagram

K0

K1

Open

0 – Lock

1 - Unlock

Red Blue Green Black