Digital circuits that adds values

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How ALU Perform decrement operation using LOGIC Zero

I google many ALU Block diagram for decrement operation.all same as shown below. This 1 bit alu perform 8 operation depending upon select line status Theoretically all operation seems works ...
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2answers
88 views

Find x cubed with half adder

My excercise is the following: Make a circuit which outputs X^3 of two bit input of X. Use the lowest number of HALF ADDERS as you can. I don't really understand ...
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1answer
46 views

Sum 4 numbers, 1 bit each, with three full adders

My excercise is the following: Make a circuit which sums 4 binary numbers, one bit each, with three full adders. My solution was the following (sorry I can't ...
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2answers
134 views

How can I add three AC signals?

I have three light sensors which outputs appropriate AC currents with respect to light intensities. I only have one pin left for my ADC IC that I have on my board so I can't sample three sensors using ...
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84 views

ALU using full adder and MUX [closed]

I am trying to implement a 1 bit ALU on Tanner EDA. I have a separate full adder and 2:1,4:1 MUX circuits. My question is: How do I interconnect the full adder to the MUXes, so that it work as an ALU? ...
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53 views

Integrated Circuit Multiplier Circuit Problem

I'm developing an 8bit x 8bit IC signed multiplier using FULL adder cells. Once I get partial products, I add them together. The problem I have occurs in this stage, adding of the products. This is ...
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1answer
60 views

Can anyone explain to me how a carry select adder works?

Doesn't get more complex then the question above. I've been looking through textbooks and using google and I feel like the explanations are not suffice or unclear. Can anyone explain this to me well?
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2answers
225 views

1bit Full Adder Cell in IC not working as supposed?

I got an adder cell, which in IC mirror layout is this: EDIT: Transistor-level, standard adder circuit: Which I actually made in IC like this: It's not working as it should! I labelled it ...
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1answer
105 views

Synchronizing multiplier with adder to form mac

I have designed an 8-bit multiplier in Verilog which takes a maximum of 8 clock cycles to give the product. I have also coded a 16 bit adder based on combinational logic. I now want to integrate the ...
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66 views

Why is my adder giving me the wrong output?

So I made this circuit right from my professor's notes. It is a carry ripple adder. I've been testing it out and one of the problems it has is this: When you turn on all three inputs, it does not ...
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58 views

How do I minimize the size of a 3-input parallel adder?

Currently this alu uses 24 logic elements, most likely from the adders. I'm wondering if there is any tool in Altera/Quartus I can use to minimize this? For my design, multiplier and RAM modules are ...
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1answer
74 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 ...
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580 views

Design of a 1-bit adder-subtractor with additional carry/borrow input

I have to design a 1-bit binary adder/subtractor unit that can both add or subtract two input values A and B depending on a control input C (it is assumed that two's complement is used). Also, the ...
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2answers
115 views

does this design look suitable for a 4-bit adder

I am working on a project that will include a basic 4-bit adder, I have designed a layout is Adobe Illustrator and would like people to check over it to see if it looks like it should work. I am very ...
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1answer
90 views

Building a small 4-bit adder on a breadboard

I am very new to using IC and basically a breadboard in general, but I am doing a project on how computers add and thought it would be nice to have a practical demonstration. My main question is, for ...
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1answer
112 views

Working of Prefix Adder

I am trying to understand the working of Brent Kung adder, but I have not been able to. All that I see in tutorials is just the figure above for carry generation. Can anybody explain it to me with ...
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41 views

3 bit x 3 bit multiplier. How to add the 3 partial products? [duplicate]

I want to implement a circuit for a 3 bit x 3 bit multiplier and i am confused as of how im supposed to add the 3 partial products. I know it should be like that : ...
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2answers
145 views

Add fixed voltage to variable voltage

I want to add two voltages. I have tried using the Op-Amp adder here. The resistor schematic before the summing amplifier contains resistors in parallel which would average the voltage. My problem ...
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119 views

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 ...
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133 views

Is there a better way to plan a circuit to square a 3 bits binary number?

I need to plan a circuit that will square a 3 bit binary number: $$\{Y_2, Y_1, Y_0\} \rightarrow \{S_5,S_4,S_3,S_2,S_1,S_0\} $$ I thought of the common way we multiply numbers and used it to plan the ...
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1answer
95 views

Complexity comparison of an adder and a multiplier

I have two algorithms with different requirements of addition and multiplication operations as follows: Algorithm 1: 100 additions 200 multiplications, total = 300 operations. Algorithm 2: 300 ...
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1answer
92 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 ...
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72 views

Construct a 16bit Full Adder for the last bits. A15 B15

How do I implement a Full Adder of 16bits for the last bits. That is, A15, B15. How does the truth table and the circuit look like for this?
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2k 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 ...
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165 views

Ultra low power adders and multiplier

I am working on a low frequency 30 khz module that needs to have an ultra low power consumption. The problem is the research focuses on improving the performance of the adders and multiplier and ...
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1answer
237 views

What happens to a 32-bit input when a gate will only output 1 bit?

For example, suppose I have a combinational circuit that takes 32 bits as input and outputs 1 bit that is equal to 1 if the 32-bits are equal to 0, and outputs 0 if the 32 bits are anything else. How ...
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4k views

What are carry-lookahead adders and ripple-carry adders?

I see carry-lookahead adders and ripple-carry adders terms being used often. I have no idea what either means (nor the type of architecture they describe). Can someone please explain what each one ...
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368 views

What is the minimum amount of 1bit Full Adders required to implement the equation 4X + 3Y + 13?

Using 1bit FAs and 0/1 constants only, while X(x1,x2,x3) and ...
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1answer
161 views

Why is carry on for an adder that is simply on? [closed]

I've understood that the behaviour is correct when I make a simple adder: But why does carry on light up just because I switch on the + operation for my 4-bit system? ...
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1answer
857 views

How to multiply using gates?

I need to multiply 2 3bit numbers. I tried that: but it does not seem to work. In this example, the output should be 49. so that is that 77?
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81 views

Choosing among adders

I'm trying to design a 4-bit adder on a transistor level design and was reading up on the best method. 'Best' here in this case refers to the smallest area, lowest delay and best performance. I was ...
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874 views

Designing a simple ALU

I need to design an ALU with two 8-bit inputs A and B and control inputs x, y, and z that supports the following operations: ...
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1answer
577 views

What is wrong with my 2-bit adder?

I attempted to build an 8-bit adder in Logisim by carefully chaining together a half-adder and 7 full adders, all made from basic logic gates. Unfortunately, it produced erroneous results; for ...
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Test Cases for 16-bit Ripple Carry Adder

I'm working on a lab for a course I have on VHDL, and part of it is to implement an n-bit ripple carry adder and then test it as a 16 bit adder. My problem is that I don't really know HOW to test it, ...
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3k 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 ...
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1answer
4k views

Determining the truth table and simplifying logic expressions (full adder)

I've been taking an intro computer architecture class and doing some research of my own, I've found the following exercise: Determine the truth table and simplify the logic expression derived from the ...
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1answer
433 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 ...
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344 views

How to design system for n bits?

Say I want to design an n-bit system e.g. 256 bits. Can I generalize a 4-bit ALU which I think I know to 256 bits? These are my diagrams.
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611 views

8 bit octal full adder help

I have this project listen below and im not sure where to start maybe someone can give me a few pointers or perhaps point me in the right direction of starting this? Thanks!! Input: A, B = octal ...
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562 views

How does one use both half and full adders together?

I am trying to teach myself the concept of (half and full) adders from Wikipedia and am a bit confused. Do I need to use both half adders and full adders together for performing multi-bit addition? ...
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392 views

How do I fit a 2 bit subtractor into its expression?

Regular Full subtractor has the following: x,y as the inputs Bin - as the borrow in Bout - as the borrow out. Bout expression: x'y + x'Bin + yBin D - difference ...
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1answer
238 views

Is this possible? produce 7 bit sum with one full adder?

i have no idea how to do this all I know is adding 2 bits with one half adder and use bunch of full adder to get a n bit sum... the original question is below Design a circuit that adds together 4X ...
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2answers
362 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 ...
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609 views

Truth Table Accuracy

I made a truth table for this sequential circuit, and I wanted to make sure that it is correct. Is this right? The top left is a full adder, and the top right is a D flip-flop.
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2k views

Critical path for Carry-Skip adder

Can anybody explain why Carry-Skip adder has the same critical path as regular Carry-Ripple adder. My textbook says that critical path occurs when carry is generated in LSB and then propagating it ...
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2answers
1k 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 ...
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1answer
966 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 ...
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1answer
5k views

How to determine overflow from an adder/subtractor?

I suppose in binary addition (no negative numbers), overflow happens when theres a carry out? Then for subtractor (2s complement), how do I determine it? From my understanding of my lecture notes, ...
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1answer
2k 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 ...