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Questions tagged [logisim]

Logisim is a logic circuit designer for creating simple and advance logic circuits such as RAMs, Registers, CPUs, and ........

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Logisim input and terminal issue

I had this final gate that I made. but when I run it in terminal. it says my output is E instead of 0/1. I wanna know why my output is E instead of 0/1. The circuit should have four inputs: A, B, C, ...
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2answers
59 views

Creating D-latch using Nand gates in Logisim?

I have designed a D-latch using NAND gates. The problem is when I convert it into a subcircuit the output is False no matter what my second input(clock input)is? It only works if I put the default ...
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31 views

How to produce a register bank comprising four such registers in Logisim, sharing common data lines D0 … D7 and outputs <Q0 … Q7>?

I made a D-Latch circuit that looks like this: and I converted it into a subcircuit and made an 8 bit register like this: But how do I make a register bank using four such registers? Any help is ...
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42 views

Logisim red wire bug

When I add a wire segment to a wire that's turned on, it turns red (even though I'm not connecting it to anything else). In fact, any wire passing over that particular dot in the schematic turns red. ...
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1answer
135 views

Unsigned multiplier

So I'm trying to build a 4-bit 2's Complement Multiplier on logisim. Here's what I have so far...The first pic is like an overview/drafting, the little chart on the right is accurate I think. The ...
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1answer
336 views

8-bit synchronous up/down counter [Logisim]

I am trying to create an 8-bit programmable up/down counter using D Flip flops. So far, this is what I have: The first 3 flip flops function correctly for both up and down, but the 4th doesn't. I ...
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1answer
542 views

How can I implement a digital clock in Logisim?

I'm trying to simulate a 12h-digital clock in Logisim. Here's the logic diagram: I could simulate BCD to 7 Segment but I don't know how to create a CTR DIV 10 and CTR DIV 6 in Logisim, so I tried to ...
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2answers
112 views

Using LED display

This is my current circuit. It's a 2 person colour guessing game. The first person will choose the colour code the other player has to try and guess using the registers on the left and then set the ...
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2answers
506 views

Multiplying numbers with number 12 on Logisim

I need a bit help/tips about solving my exercises. So I got the excerise as follow: Im gonna multiply all 4-bit numbers (0-15) with the decimal number 12. Now, 12 is 1100. Input is going to be 4 bit,...
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1answer
105 views

Logisim ROM Output not matching address input

I'm getting this really weird problem when trying to use the built in ROM chip in Logisim. First off, even though I specified a 16-bit data bit width, the ROM only stores 4 bits per address (isn't ...
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1answer
337 views

How to make shift register logisim

How would i make a 4 bit shift register with d flip flops so that only 1 led is active at once. So for example if a button was pushed the first led would light up and the other 3 would be off. If the ...
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1answer
500 views

Blue wire in logisim

I created this circuit and at first all the wires were green but when I copied it out of the main folder into another one, the wires turned blue. I've tried messing around with it and looking up what ...
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235 views

SLT in Logisim help

I have designed an ALU in logisim that can do arithmetics like add, sub, and/or. I am also trying to design the slt function. Basically when F is 111, if A < B then the ALU should output value 1, ...
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1answer
341 views

New to circuits: Creating a toggle button in Logisim using Latch

I have just started doing logic and circuits and I am trying to make a toggle button using a button and a latch. I can't seem to figure out how to make the light toggle instead of turning on when the ...
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1answer
156 views

Custom-built NAND SR latch not resetting

I'm trying to build SR latch in Logisim using NAND gates, but I seem to be unable to get the latch to truly reset. I can set S to 0 and R to 1, but once I set it back to 0, Q goes back to being 1. How ...
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1answer
74 views

how do I use a multiplexer to select a logic function to use?

I have a homework assignment where I'm supposed to use 4:1 multiplexers to select from one of four logic functions in Logisim. However, my only experience with multiplexers in Logisim up to this point ...
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1answer
177 views

How to simulate a FIFO in Logisim

I'm looking at prototyping a design I plan to build using logisim. The design will make use of a FIFO IC (74HC40105) as a buffer between a data producer process and a data consumer process. I can't ...
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731 views

How to write a program for 4-Bit CPU made in Logisim?

So I finally got my 4-Bit CPU working on Logisim, and am trying to get it to do commands and display them, but am unable to do so. My CPU looks like the following: I am trying to implement the ...
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2answers
114 views

Is this an encoder? Correct naming of circuitry

Newby to the digital circuitry world please be nice. For a rock paper scissors game, I've created the following to determine a winner, however I don't know what this circuit would be called in the ...
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1answer
537 views

Divide by N clock/frequency

I need to create a clock divider which has 2 inputs: n(12 bit) , clock. For every even N it needs to divide the clock frequency by that number. (2,4,6,8 etc). However I have run into some problems. ...
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1answer
217 views

Don't Understand the Notation on this State Diagram

This like a simple question, but I can't find a clear answer anywhere. Basically, I am used to seeing and implementing state diagrams that look like this: Where the output and input are in this ...
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2answers
348 views

Logisim sidebar disappeared

How do I get the sidebar back? I minimized it in an attempt to get more screen space but I cannot seem to get it back.
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2answers
352 views

Logisim Problem

I designed two or latch, one with or gate, and another one with transistors, but the one I designed with transistors wont work as expected. Can anyone please tell me if it has a logical problem or if ...
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121 views

Help implementing a synchronous circuit in Logisim

I am trying to implement the following circuit in Logisim, yet all I get is y=0. Any idea what might be the problem? As the original circuit seems to be correctly implemented I would guess that the ...
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2answers
2k views

Help using MUX in Logisim

I am experiencing difficulties using Logisim whilst trying to implement a simple 2-to-1 MUX. I keep getting "Incompatible Widths" error messages no matter how I connect it. Any idea what's causing ...
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1answer
424 views

How to design a control bit to turn unsigned binary into two's complement?

I am designing a 4-bit comparator using only basic logic gates (and, or, nand, xor, etc.) In its current form, the comparator takes two 4-bit unsigned binary numbers (A and B) and compares each bit ...
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1answer
656 views

Comparator on Logisim

Currently working on an elevator circuit. I am using 4-bits to represent the floor that the elevator is on, and I need a way of comparing this value to the floor that the user wants to get to. I am ...
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1answer
633 views

Logisim Adder Circuit

I was trying to add 0xA5 and 0x44 by using adder circuit and connect Hex Digit Display to show. however, the Hex Digit Display doesn't show me anything and the result also not right. i would ...
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1answer
175 views

How to simplify a multiplicator that currently consists of many adders?

I have created a circuit with 64 AND gates, 77 1-bit adders and one OR gate. I am trying to create a 8 by 8 multiplier. How can I simplify this circuit, especially using the 8-bit adders?
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1answer
5k views

4 by 4 bit Multiplier. Logisim help

I am trying to recreate the following design: When I create it in Logisim, this is the error I get: I understand the incompability is due to the number of data bits. When I adjust the data bits, ...
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1answer
755 views

How Do I Expand the Divider?

I'm trying to make a 128-bit divider in Logisim using Logisim's built-in arithmetic library. How do connect the dividers so that I can work with division of greater than 32-bits? What I have ...
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1answer
470 views

AND gate, red wires logisim

I have these and gates. When I disconnect one of the red wires from its corresponding gate, the other goes green. But if they're both connected it goes red. From what I've read in the documentation, ...
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2answers
199 views

Can a button toggle a 1-bit pin?

I know that buttons, when pressed will send a value of one, but when released will go back to zero. So what I'm asking is can a button TOGGLE a one(or more) one bit pin(s)? I'm using Logisim, but I ...
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4k views

Very simple CPU design in LogiSim

I'm currently a junior in highschool, and I've been interested in computer/electrical engineering, specifically microprocessor design. I've read Code by Charles Petzold, , and have begun reading the ...
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1answer
644 views

Stopping RAM from Writing in Logisim

One of my labs for my computer science hardware organization class has us designing a simple memory circuit. It uses RAM memory with 16 4-bit values. The description is as follows: "Build a circuit ...
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1answer
314 views

How do I transition from one state to another with d-flip-flops? (digital lock)

I am currently trying to make a digital lock for an assignment, the code in this example is hardcoded 1-2-3. This is what I have so far: x0,x1,x2 are the BCD input for the lock. I am trying to make ...
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2answers
9k views

4 to 1 multi-bit multiplexer implementation [Q]

We are tasked with creating a 4 to 1 multiplexer with 4-bit inputs. I believe I fully understand how to create a 4 to 1 1-bit multiplexer, but I completely do not understand what the 'input' side and '...
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2answers
5k views

How do you convert a number to its 4-bit binary equivalent using logic gates?

Circuit storing number as binary ]2 My aim is to store numbers from 0-15(4 bits) as binary. The numbers are inputted using a keypad with buttons labelled N0-N9. The circuit works for single digit ...
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1answer
338 views

Function of demultiplexers in Register File

What is the function of demultiplexers (DMX) in this Logisim diagram of a Register File design: Also could you explain the meaning of: dreg,sreg,treg dsel,ssel,tsel dwrite,swrite,twrite
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1answer
445 views

How do you store a number entered through keypad buttons in D flip-flops? [closed]

In the circuit, only ONE value from N0-N9 will be high. So, only one of the OR gates will have a HIGH value. I need to use only the HIGH output from the OR gates output. I tried using a multiplexer ...
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1answer
483 views

Initial Error State In Logisim, Alternate Solution?

I am currently working on this problem for a computer systems class and have nearly (touch wood) found a solution. The solution I have right now correctly does what the brief asked for BUT starts with ...
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2answers
512 views

Paralell SRAM with separate I/O ports

In Logisim I created a circuit containing RAM module with separate input and output lines I want to build this circuit from real items. However I could not find any SRAM chips that have separate I/O ...
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2answers
697 views

How does logisim differ from redstone and real life circuitry?

I recently developed an interest building circuitry systems. It started in Minecraft and then grew when I picked up a micro controller from Radio shack to build an RC car with. Obviously I'm most ...
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1answer
246 views

Is my understanding of D-Flip Flop wrong?

So I am working on: http://www.nand2tetris.org/ and I am having a hard time understanding the D-Flip Flop, or maybe I should say, how Logism represents it. I have this circuit and this is the current ...
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1answer
4k views

Red wire in logisim

I have been messing around with logisim and I am fairly new and I cant figure out why I am getting this red wire. In the picture is my memory which is currently reading from the top left cell and ...
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5answers
3k views

Counter with 4 flip flops jk synchronous from 3 to 13!

I have to create a counter with 4 flip flops jk synchronous. The counter shall count in this order: 3 to 13 and then to 3 to 13 and so on.. I have to use logisim simulator. Ok. So i think its ...
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1answer
447 views

How does this reverse NOT gate work?

I created a 74LS181 circuit in Logisim based on TI's datasheet. Notice how the NOT gate for the B0 input has a dot before the triangle: Here's a screenshot of my circuit: Notice that my inversion ...
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1answer
3k views

What does a blue line indicate in Logisim?

I know dark green indicates 0, bright green indicates 1, orange indicates incompatible bit width, but what does a blue line indicate?
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3answers
6k views

Logisim: “Oscillation apparent”

I am trying to simulate an RS master slave flip-flop in Logisim, and I have encountered the "Oscillation apparent" error. What does this error mean and how is it resolved? I am required to use two nor ...
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1answer
4k views

Digital Circuit with Toggle Switch using Logisim

I'm supposed to design a small digital circuit (with Logisim) using basic logic gates, so that when this circuit is used with the chosen switch (which has to be a button), it will make the circuit ...