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# Questions tagged [truth-table]

A truth table is a mathematical table used in logic—specifically in connection with Boolean algebra, boolean functions, and propositional calculus—which sets out the functional values of logical expressions on each of their functional arguments, that is, for each combination of values taken by their logical variables.

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### LT spice, JK Flip Flop: Wrong behaviour when J K and Clock are high

Here's a picture of a JK Flip Flop I try to simulate with NAND gates: This is the behavior I would expect; if Clk, J and K are all high, Q_n+1 should be negated Q_n: However this is what I'm ...
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### Combinational Circuit: How can 2.5 and 3.5 be represented in a 3-bit truth table?

Design of a combinational circuit with 3 inputs, x, y, z, and 3 outputs, A, B, C. When binary input is 0, 1, 2, or 3, the binary output is twice the input. When binary input is 4, 5, 6, or 7, binary ...
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### Reducing a given truth table with don't cares at inputs

I searched quite a bit about this but it seems not many people have a similar interest as mine regarding don't cares. Most don't care topics I found revolve around simplifying the function at hand. I ...
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### Help with truth table and K-Maps [closed]

I am currently working on a traffic light system, the state transition table developed for the project reads as follows: I have additionally used Neeman's Digital software to create a table (and K-...
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### Transition table from state truth table

Assuming a simple binary state variable allocation can be made and that any unused states can be treated as don’t cares. How would I Design a corresponding transition table for this system including ...
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### Did I create this Karnaugh map correctly?

I'm tasked with making a 4-7 decoder for a 7-segment LED (common anode). I am an extreme layman (1st year EEE student) I have 4 inputs (A,B,C,D) ...
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### Will the Karnaugh diagram change when you use gray code on the truth table?

I am currently trying to put this state diagram into a truth table: I wrote the truth table like this: When I try to get the expression for q1+ I get: q1+ = q1q0' + q1q0x, but I can apparently get: ...
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### Query regarding 9 V battery connection to 7408 IC

I have got some LEDs, a breaboard, a 74HC08 IC, a 9 V battery, resistors of 10 and 100 ohms. I want to check the IC by connecting it to a breadboard but the IC input voltage is 5 V and current 8 mA. ...
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### How do you cascade two 7-segment decoder ICs together?

We used one 74LS47 IC in our lab, which we connected to a 7-segment display and tested the outputs. Now our instructor has told us to cascade two 7447 ICs together and implement it on a 7-segment ...
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### 7-segment display decoder truth table

I am trying to make a decoder that can display all alphabetical letters on a 7-segment display. My inputs are ABCDE and the outputs are abcdefg Is this the correct truth table for a circuit? If yes, ...
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### Difference between waveform and truth table [closed]

Is there a difference between waveform and truth table to represent the values of a circuit? For example: Are there particular cases where one or the other should be used?
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### Convert boolean expression to nand gate only. X = A'B'C+AB'C'+A'B'

I have already made a diagram. However, it won't match the truth table that I have made, which I got from the logic converter in multisim. Could you please help me out with where did I go wrong? Is it ...
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### How to fill flip flop clock truth table? [closed]

I have this truth table that I want to fill, however, I have no idea how to read the flip-flops on the left. Can anyone provide me a minimal example of how to approach this problem? EDIT: drawing ...
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### Creating truth table

I want to create a truth table to see all options for 74HC123 output. Basically an optocoupler output is connected to 74HC123 as input. 74HC123 will get the data from optocoupler. There could be two ...
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### Truth table - which is right?

So i've got a question to build a truth table for a controller circuit I've to build. From the wording of the question I'm unsure which of my truth tables are correct (if at all). The controller ...
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### If two Boolean functions $f_1$ and $f_2$ have same truth table, does that means they have exactly same characteristic? can one f1 numerate to f2?

if $f_1(x,y,z)=\neg xz+x\neg y+\neg xy\neg z+xy\neg z$ determine if $f_1$ is symmetric and whether it is unate. What I thought is: $f_1$=¬xz+x¬y+y¬z, the truth table of $f_1$ has the same ...
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### How to get the truth table without the expession? [closed]

I am in my first year at university and I have been given the following assignment: Implement a support system for the safety of passengers inside motor vehicles. The system must ensure that the ...
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### Reading the Boolean Expression for a Logic NAND Gate

From https://www.electronics-tutorials.ws/logic/logic_5.html I learned that Boolean Expression for a 3-input Logic NAND Gate is , and is read as "A AND B AND C gives NOT Q". I am wondering ...
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### Why doesn't this circuit simulation work?

I am trying to build a circuit using only encoders and decoders. This circuit will output the 1’s complement of 3 bit number. (For example: If I give it 010 it will give output 101.) I used a ...
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### How do I verify my solution is correct for a circuit diagram?

The original problem: The trouble I'm having is that I'm not sure at all if my boolean expressions from the circuit diagram for (1) are correct; I also know that I ...
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### Missing data in truth table and commenting on missing value

I was trying to solve the attached question from the book Digital Design: With an Introduction to Verilog HDL, 5e however the values of f1 and f2 for the entry (1,1,0) are missing. If we use sum of ...
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### FSM binary number divisible by 5 truth table

I am having trouble seeing if my truth table based on the exercise's instructions is correct (mostly because the instructions are really confusing me and the TA's explanation really didn't help, this ...
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### Designing lookup table(LUT) for half adder in FPGA

I want to implement half adder using FPGA. For this I need to design CLB, more specifically LUT for half adder. I know LUT gives only one output. But, for half adder we get two output. One for sum and ...
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### SOP and logic expression for a circuit

I'm having trouble doing the Sum-or-product of this truth table and then simplifying the logic expression. For the SOP i got Y= A’.B’.C’.D’+ A.B’.C’.D’+ A’.B.C’.D’+ A’.B’.C.D’+ A’.B’.C’.D+ A.B.C’.D’+ ...
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### how to verify truth table of MAX485/RS485

I want verify 2nd case of the below truth table of MAX485 IC (RS485). Please see in red color. Is my circuit correct ? I have connected RE,DE and A-B to GND for making it LOW.I have connect DI to GND ...
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### What logic gate matches the truth table below?

I'm just wondering what logic gate has two inputs and only outputs HIGH if one of the inputs is HIGH. Here's a truth table: <...
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### Maxterm: misinformation or different approach to understanding

I have found myself in a crossway of two different explanations regarding Boolean algebra, Maxterm. However, I cannot grasp, whether there is a trick to it or whether one of explanations is an actual ...
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### Design circuits with unused inputs or has a constant expression

I just started to learn about circuits design (without any prior experience), as a result I would like to ask a question. I was given a truth table for a circuit that has three inputs, and I need to ...
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### Can I use ANDs as Tri State Buffers?

I’m working on a 4 bit computer/calculator that’s fully NAND (just for the heck of it) and I needed some tri-state buffers for the registers. I think that using an AND works the same, but nowhere ...
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### Can someone double check if my truth table make sense to the problem statement?

Just wanted to double-check. Thanks in advance.
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### How are LUTs in a FPGA filled?

I know there have been a lot of questions about lookup tables and their design, but even after reading them and scouring the web, I still don't quite understand how the LUTs are filled with ...
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### Design a 4-bit binary counter using D flip-flop

I am learning logic circuit now.I am going to design a 4-bit binary counter with D-flip-flop.It counts from 0 to 15.And when the number reaches 15,the number wont change and remains 15.I am now ...
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### 3 input logic gate

I really need help because I need to come up with a circuit with 3 inputs (input A, input B and input C) and a truth table where in every case except for when input A and input C are 1 the output is 1....
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### Design a combinational circuit with two inputs and four outputs. The output binary number should be the square of the input binary number

I don't know how the output expression for each output produced from the truth table. Can someone please explain how this output expression was dervied from the truth table? Problem: Design a ...
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### Simplifying a MUX's truth table

I found this truth table for a 4-to-1 MUX: (circuit for context) I know (I think?) that if I were to make a truth table with 2^6 variables and simplified it I'd get the same SOP as I'd get with this ...
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### Understanding complements on inputs

I've got a problem understanding formal writing down of complements on inputs. During my laboratory exercise I was working with a device that had D flip flop embedded in it. The goal was to ...
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### Sum-of-Product understanding

I am trying to learn Sum-of-Products and minterms and maxterms for logic design, but I don't know how the book gets the f(x1,x2,x3) part. I think I understand the minterm from the first pic (it's ...
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### How does carry in work in full adders?

Yesterday I asked a similar question and realized I still don't quite get it, so I'm sorry about that. Here is explicitly what I mean: This is a part of a full adder. The first row in which ...
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### binary addition / truth table?

I'm trying to understand how binary addition works. If I understand it correctly, with two variables e.g. x and y you add a ...
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### Writing Truth Table Given Function

so I am taking a summer course and the teacher is not so helpful at the moment so I was thrown the following question to do: Derive a truth table for the following function: \\$f(x,y,z)=\sum m(1,3,5,7)...
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### Truth Table does not exhaust all combination. Can it be translated to a circuit? Is it ill-pose?

Step|A|B|C ---------- 1 |0|0|1 2 |1|0|1 3 |1|1|0 4 |1|0|0 From the truth table above, I can not find the equivalent boolean expression hence I can not ...
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### Name for this logic operation [closed]

I'm from math.stackexchange and I wanted to know the name of an operation on multiple variables. I thgouth what I wanted was the XOR gate, but this is not the case. When I looked on this site I ...
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### How can I draw the diagram using few decoders for this truth table?

For the truth table above, abc is the input and xyz is the output. I do know how to draw the diagram using a decoder in case of when I have only one output. How can I draw the diagram using a decoder ...
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### What are the names of all possible logic gates with 1-or-2-bit input and 1-bit output?

This seems to be a silly question, but the fact is that when I tried to search for related information, none of the search results gave me satisfactory answer. Logic Gates with 1-bit Input and 1-bit ...
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### What does this extra notation mean when writing a sum of products expression from a truth table?

So I am practicing for an exam in digital electronics. I am doing some exercises on writing expressions from truth tables, and I came across a description for the columns that should be true and false ...
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### Rising Edge-Triggered Truth Tables

I'm trying to debug some issues in an old (early-90's is old now, isn't it?) circuit, and noticed something in at least two different chip's truth-tables, and thought I'd ask here.. In the 74LS74 (...
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### Addition and subtraction of binary digits

I have to solve the following exercise : Extend the circuit of the first part (the first part was an adder of integer numbers of 2 binary digits) in order to execute addition and subtraction of ...