# 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.

29 questions
Filter by
Sorted by
Tagged with
1answer
89 views

### 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 ...
0answers
30 views

### 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 ...
1answer
34 views

### 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 ...
0answers
334 views

### 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 ...
1answer
191 views

### 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 ...
1answer
57 views

### 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’+ ...
1answer
60 views

### 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 ...
2answers
140 views

### 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: <...
1answer
65 views

### 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 ...
1answer
35 views

### 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 ...
2answers
146 views

### 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 ...
1answer
58 views

### Can someone double check if my truth table make sense to the problem statement?

Just wanted to double-check. Thanks in advance.
2answers
290 views

### 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 ...
1answer
77 views

### 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 ...
2answers
101 views

### 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....
3answers
505 views

### 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 ...
2answers
203 views

### 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 ...
0answers
179 views

### 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 ...
2answers
440 views

### 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 ...
2answers
88 views

### 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 ...
4answers
698 views

### 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 ...
1answer
43 views

### 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)...
2answers
188 views

### 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 ...
3answers
140 views

### 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 ...
1answer
44 views

### 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 ...
2answers
1k views

### 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 ...
1answer
47 views

### 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 ...
1answer
91 views

### 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 (...
2answers
76 views

### 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 ...