17067688.ppt

digital electronics

1. Half & Full Subtractor
•Half Subtractor
•Full Subtractor

2. Half-Subtractor
•Function Table
•Expression
•Logic Circuit

3. Half-Subtractor Function Table
Input Output
A B DifferenceBorrow
0 0 0 0
0 1 1 1
1 0 1 0
1 1 0 0

4. Half-Subtractor CircuitBABABADifference  BABorrow'

5. Full-Subtractor
•Function Table
•Expression
•Logic Circuit

6. Full-Subtractor Function Table
Input Output
A B C DifferenceBorrow
0 0 0 0 0
0 0 1 1 1
0 1 0 1 1
0 1 1 0 1
1 0 0 1 0
1 0 1 0 0
1 1 0 0 0
1 1 1 1 1

7. Difference ExpressionABCCBACBACBAD  )()( BCCBACBCBAD  )()( CBACBAD 

8. Borrow ExpressionABCBCABCACBABorrow  ''''' BCCABABorrow  ''
1
1 1 1

9. Full-Subtractor CircuitBCCABABorrow  ''
-Draw the circuit

11. Full-Subtractor based on
Two Half-Subtractors
Full-Subtractor = Half-Subtractor + Half-Subtractor

12. Parallel Binary Subtractor
•Multiple Single bit Full-Subtractr connected in
Parallel

13. 4-bit Parallel Subtractor
1100
0101
____________
0111

14. •A complete logical circuit capable of adding or
subtracting two numbers by using 2’s
complement is shown in Figure below
Binary Adder and
Subtractor