Design of XS-3 Adder and Subtractor Using IC 7483
Introduction
Objective
- o Design Xs-3 Adder and Subtractor circuit using digital logics
- o Take input in decimal form
- o Show result output on 7 segment displays
Design Concept and
Implementation
Xs-3 Adder Subtractor circuit is
based on basic algorithm of xs-3 addition and subtraction. In Xs-3 addition we
convert decimal numbers into BCD adds 3 into each digit before writing; then we
do simple BCD addition but if carry is generated then we add 3 (0011) into that
nibble if carry is not generated then we subtract 3 (1101) from that nibble.
In this project we have made 8-bit Adder subtractor circuit and we took a
Input in decimal and converted that decimal into BCD by using IC 74LS147
then added 3(0011) into each nibble by using adder IC 7483 by this we
got required Xs-3 number; then, I created 8-bit adder subtractor circuit by
using IC 7483 and gates. The final results are shown on 7 segment displays by
using IC 7447 driver.
To switch on the Subtractor
circuit there is one logic state (K) on right side of circuit and also shown in circuit below which default state
is zero that is addition mode; if we set it 1(high) then by XOR circuits the
inputs, let’s say B is converted into B’ and by 2’s complement while adding one
into B’ it gives final result as -B. Then by the adder circuit it becomes
A+(-B) = A - B.
If we subtract 3 from final
output decimals we get actual answer of sum.
Example
Calculation
50 + 54
Step 1:
Convert digits to XS-3.
5 → 1000…. (5+3=8)
0 → 0011…. (0+3=3)
5 → 1000 …. (5+3=8)
4 → 0111…. (4+3=7)
Step 2: Add using binary adder.
Step 3: Apply correction rule.
Add 3 if carry is generated anyways subtract 3.
Final output → 104
Circuit:
Simulation of XS-3 Adder circuit designed in Proteus
Conclusion
The XS-3 adder and subtractor was successfully implemented using standard digital ICs. The circuit demonstrates how decimal arithmetic can be implemented using Excess-3 coding and binary adders.
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