Microsoft Word - Digital Logic Design v_4_6a

Solution:

1) Draw the system diagram and Identify input and output variables..

• Input and output value definition:
  Ki =1 when key “i” is pressed and K i =0 when key “i” is not pressed.
  L 0 =1 causes the lock to open

2) Write out the truth table for the function:

Input Output

K 0 K 1 K 2 K 3 L 0

0 0 0 0 0

0 0 0 1 0

0 0 1 0 0

0 0 1 1 0

0 1 0 0 0

0 1 0 1 1

0 1 1 0 0

0 1 1 1 0

1 0 0 0 0

1 0 0 1 0

1 0 1 0 1

1 0 1 1 0

1 1 0 0 0

1 1 0 1 0

1 1 1 0 0

1 1 1 1 0

3) Use K-map or CAD to minimize the function and write the algebraic function.

Key

Controller

K 0

K 1

K 2

K 3

L 0

K 0 K 1 K 2 K 3

Keypad