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Questions tagged [carry-look-ahead]

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Adding four numbers of 1 bit each and then cascading them

When I add four bits (NOT FOUR BIT ADDER, only four bits), the result can go to a maximum of 100 (4 in decimal, if all are ones). Now, here 0 (LSB) is the sum and 10 is carry. If I want to transfer ...
Shehryar Kashif's user avatar
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137 views

Concept of Booth Encoded Multiplier 8bit

So I'm kinda a newbie in this world so pardon me for the basic questions. I want to implement Booth encoded multiplier 8bit. Until now, I pretty much understand for the block diagram and what happened ...
noc's user avatar
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Carry-select adder - Time calculation

a) Suppose a binary pick-up adder (carry-select) of 32-bits, comprising 4 sub-sections adders spreading carry of range 8 bits. Show the values ​​obtained internally in the circuit of this adder to ...
Mary Star's user avatar
4 votes
2 answers
13k views

Carry Look Ahead adder propagation delay calculation

I'm studying Digital Design and Computer Architecture book, I'm stuck in the section of the carry-lookahead adder because there's something that I don't fully ...
Tortellini Teusday's user avatar
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1 answer
177 views

Implementing Carry look ahead Unit in logism

I'm quite new to logism and circuits and I have an assignment about implementing a carry look ahead unit. I Just want some help in regards to clearing some of my confusions to carry look ahead units. ...
Jr194's user avatar
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764 views

How to cascade multiple look ahead adders

I know how we can prepare 4 bit look-ahead carry adder (CLAs) to avoid delay involved in rippling of carries in ripple carry adder. We calculate various signal in CLA as follows: Carry propagate ...
RajS's user avatar
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2 votes
1 answer
265 views

Designing a Carry lookahead unit using EEPROMs, creates oscillator

I have read something about CLUs (Carry Lookahead Units) and want to build one. I have settled on a design using EEPROMS as ...
Kralik_011's user avatar
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1 answer
580 views

CLA Propagate Term: Xor vs Or Gate

Okay say I have to use a CLA adder to implement the addition of two 2-bit numbers, X = x1x0, Y = y1y0. And say I have to write down the logical expression for the final carry-out. So C1 or the first ...
Krish Khatri's user avatar
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340 views

carry look ahead adder

An N-bit carry lookahead adder, where N is a multiple of 4, employs ICs 74181 (4 bit ALU) and 74182 ( 4 bit carry lookahead generator). The minimum addition time using the best architecture for this ...
Geeklovenerds's user avatar
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1 answer
964 views

Some questions about carry-lookahead adder and ripple-carry adder

I was reading about the carry-lookahead adder and about the ripple-carry adder. I saw some designs and it made me wonder about a few things. Both questions are the same for both adders, so I'll call ...
vesii's user avatar
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-2 votes
1 answer
3k views

Trouble with 8-bit Carry Lookahead Adder in Verilog

I'm new to Verilog programming. I'm trying to work up to a 64-bit CLA by building a 4-bit CLA, then an 8-bit (out of 2 instances of a 4-bit), then a 16-bit (out of 2 instances of the 8-bit one). I'll ...
enharmonics's user avatar
1 vote
1 answer
5k views

Time complexity of carry look ahead adder

How is the time complexity of carry look ahead adder O(log n)? Can you explain in terms of gate delays?
Arteezy's user avatar
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Carry-lookahead adder in VLSI, Static VS Dynamic?

I study one course about VLSI. in adder lecture my profesor talk about Adders. in Carry-lookahead adder first talk about static version, as follows: at next we start about dynamic version of CLA and ...
Johnatan Morian's user avatar
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1 answer
743 views

8 bit adder with 2 CLA

I need to make an 8 bit adder with 2 4-bit look ahead adders.I spent a lot of time reading about it and I think I get the gist of how it works, but I can't seem to get this. I spent a lot of time ...
user3728320's user avatar
1 vote
1 answer
2k views

calculate clock cycle of ripple Carry and lookahead adder

How would you find the number of clock cycles it takes to produce sum, the carry out, and overflow flag using ripple carry or lookahead adder. Can someone please explain me how would we go on finding ...
Abhi's user avatar
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1 answer
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Arithmetic Circuits (ADDERS!)

I usually only become a passive reader in this forum, but today I decided to ask my first question. How many logic gates required for a 4-bit Carry Look Ahead adder and Prefix adder? I know that ...
John's user avatar
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1 answer
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Carry look ahead adder with 2-input gates?

I would like to make a 8 bit adder, with carry look ahead, but i only have 2-input logic gates. All I've heard about use some at least 4-input gates. Or do I need to use a totally different method, ...
user avatar
2 votes
1 answer
7k views

How to find gate delay for 4-bit look-ahead carry adder?

How can I find Gate Delay for bit 1 of the sum by a 4-bit look-ahead carry adder?
Rohit Gulabwani's user avatar
3 votes
2 answers
12k views

Delay in 4-bit ripple carry adder?

In pic below I have drawn a full adder and mentioned their delays, please help me to verify my answer.
Vikrant Singh's user avatar
2 votes
1 answer
7k views

How do carry save adders work?

I thought I understood the concept but wikipedia has confused me. There are two outputs because one's for a partial sum and one's the carry bits. But why must it be used to "compute the sum of three ...
Celeritas's user avatar
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2 votes
0 answers
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How to compare carry-lookahead and ripple-carry adders?

I am a bit stuck with the concept of carry-lookahead adder so I'd like to compare it with another concept I'm more familiar with: the ripple-carry adder. I'm trying to make some basic math comparison ...
Giuseppe Crinò's user avatar
-3 votes
1 answer
172 views

Design of an adder circuit

I have a adder circuit consisting of carry look ahead adders. However, I am not allowed to use the generate function to determine the sum of the two numbers. I am allowed to use basic logic operations(...
alpha42's user avatar
0 votes
1 answer
4k views

Multiply 4 Digit Binary Number By 3 - Circuit

I want to find a way to multiply a 4 digit binary number by 3. I have this circuit that doing this process and I don't understand how it works. To multiply a number by 2 I need to shift the digits ...
Ofir Attia's user avatar
2 votes
1 answer
36k views

How to calculate Gate Delays in normal Adders and Carry Look Ahead Adders

In my textbook the gate delays for the n-bit ripple adder is given as \$ 2n \$ for \$c_n\$ bits and \$ 2n-1 \$ for \$ s_n-1 \$ for the circuit as shown below: But, for a 4-bit Carry Look Ahead Adder ...
Gowtham's user avatar
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1 vote
1 answer
7k views

Carry Look ahead adder Propagate & Generate Outputs

I am taking comp architecture course, and we are given a task to write 32 bit look-ahead adder in VHDL. Instructor provided the instruction and diagram. While reading, Wikipedia article, I stumbled on ...
newprint's user avatar
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3 votes
1 answer
805 views

Carry-lookahead adder - what happens to carry bit?

I recreated and trying to understand for the sake of fun and learning the circuit that can be seen here on second page: Link . This is basically a 4-bit carry-lookahead adder, but there is one thing ...
Łukasz Zaroda's user avatar
3 votes
2 answers
757 views

Why does design_vision compile my carry-lookahead adder into a ripple-carry adder?

At my school we have Synopsis "design_vision" in the computer labs. I don't know how to use any of the features so to me it's just a schematic-drawing tool. Out of curiosity, I hand-coded in Verilog ...
Owen's user avatar
  • 747
5 votes
3 answers
6k views

How to determine if a Carry Look Ahead Adder Overflows

I am implementing a 32 bit CLA Adder like how a 16 bit adder is implemented in Wikipedia Problem is how do I determine if the block overflows? I will need the carry into bit 32 (which is now in the ...
Jiew Meng's user avatar
  • 579
1 vote
1 answer
5k views

Whats the difference with Carry Look Ahead Generator & Block Carry Look Ahead Generaor

Whats the difference between this 2 CLAG (Carry Look Ahead Generator) CLAG Block CLAG I mean, the way Carries of 1st 3 bits are the same and the last carry is actually \$G*\$? The difference is use ...
Jiew Meng's user avatar
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2 votes
1 answer
3k views

Carry look ahead adder/subtractor & Overflow, Negative Bits

I am suppose to design a carry look ahead adder with ... Input flag bits E (Enable) S (Subtraction) Output The usual sum & carry out O (Overflow) N (Negative) Z (Zero) But the question is ...
Jiew Meng's user avatar
  • 579
2 votes
1 answer
7k views

How does this carry look ahead block work?

This is a carry look ahead adder : This adder is known to calculate one or more carry bits before the sum. From the figure we see that carry look ahead block calculates the carry C1,C2,C3,C4 . But i ...
Suhail Gupta's user avatar