Register to reply

16-bit addition/subtraction with an 8-bit adder

by cyenko
Tags: 16bit, 8bit, adder
Share this thread:
May13-12, 05:37 PM
P: 4
1. The problem statement, all variables and given/known data

Suppose we have only one 8-bit ripple carry adder but need to do 16-bit addition and subtraction.
Design a sequential circuit (FSM) with only one 8-bit ripple carry adder to implement a 16-bit adder-subtractor.
You are allowed to use MUXs and need to generate the overflow signal.

2. Relevant equations

Overflow = Cn - Cn-1

3. The attempt at a solution

I've attempted to find similar circuit schematics, boolean expressions, diagrams, etc. online to no avail. I am familiar with the implementation with an 8-bit ripple carry adder, and can obtain the final overflow signal through

Since I am prohibited from using two 8-bit adders, I was thinking of encoding the given 16 bit numbers using a 16-4 encoder, and then doing the operations, but this would not be valid when multiple bits of the given 16-bit numbers are set high.

I'm looking for guidance on where to begin. I think once I have the general idea on how 16 bits can be stuck in the 8 bit adder, I'll be able to do this problem. Specifically, where should I route the overflow to, and what combination of bits from the two original numbers should I put into the adder?

Thanks for your time,
Phys.Org News Partner Science news on
Physical constant is constant even in strong gravitational fields
Montreal VR headset team turns to crowdfunding for Totem
Researchers study vital 'on/off switches' that control when bacteria turn deadly

Register to reply

Related Discussions
Addition and subtraction in machine language Engineering, Comp Sci, & Technology Homework 12
How does colour addition / subtraction work? General Physics 27
How do I introduce my kid to addition and subtraction? Educators & Teaching 6
Vector addition and subtraction Introductory Physics Homework 2
I need help with vector addition and subtraction Introductory Physics Homework 2