Aim: Implement full subtractor using 8 to1multiplexer.
Apparatus : Digital Trainer kit, single strand wires, breadboard, NOT Gate NAND (IC-7400).
Theory :
Full subtractor:
A full subtractor has three binary inputs(subtrahend, minuend and one borrow bit from the previous subtraction operation). It produces two binary outputs(difference and borrow) using a combination of logic gates. The borrow given to the previous subtraction operation is denoted as Bin
In full subtractor, eight possible operations are possible with three inputs and produces eight, two digit outputs. The operation is shown in the truth table below.
Truth table for full subtractor
For difference and borrow outputs, boolean expression has to be derived using Karnaugh map. Since it has three input variables, 8-cells k-map is used to simplify the expression.
The boolean expression for difference output can further be simplified as follows.
Now we have two boolean expressions for difference and borrow output. With those expressions, the combinational circuit for full subtractor is implemented.
Logic circuit for Full subtractor
PROCEDURE:
I. Place the breadboard gently on the observation table.
II. Connect the wire to the main voltage source (Vcc) whose other end is connected to last pin of the IC .
III. Connect the ground of IC to the ground terminal provided on the digital lab kit.
IV. Connect output pins to the led on digital lab kit.
V. Switch on the power supply.
BY: VISHAL
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