Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [carry-look-ahead]

30 questions
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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 last 4 bit CLA Adder) and XOR with carry out of…
Jiew Meng
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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 understand about the propagation delay of an N-bit carry-lookahead adder. The book…
Tortellini Teusday
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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 that I cannot understand. If there will be 1111…
Łukasz Zaroda
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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 an 8-bit carry-lookahead adder, and then asked…
Owen
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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
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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 between the two ones. Assuming every gate can…
Giuseppe Crinò
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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 have 3 gate delays for all carry bits and 4 gate…
Gowtham
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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 adders and CLU. In the picture below, you can see a schematic CLU implementation. In my version, I think the best would be to…
Kralik_011
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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 vague ... It says if E = 0, S = 1, do subtraction E…
Jiew Meng
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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 don't understand how does it do that ? How does…
Suhail Gupta
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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
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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 or more n-bit numbers" why can't it compute 2…
Celeritas
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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 perform the addition of the numbers…
Mary Star
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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 the following diagram. Since C4 is already…
newprint
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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
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