Digital Logic - Old Questions
3. Design the full subtractor circuit with using Decoder and explain the working principle.
10 marks
|
Asked in 2065
Full subtractor contains 3 inputs and 2 outputs (Difference and Borrow) as shown-
The truth table for full subtractor:
From the above truth table,
For the different functions in the truth table, the minterms can be written as 1,2,4,7, and similarly, for the borrow, the minterms can be written as 1,2,3,7.
Since there are three inputs and a total of eight minterms. So we need 3-to-8 line decoder. The decoder generates the eight minterms for A, B & Bin.
Fig: Full subtractor with 3-to-8 Decoder and NOR gates