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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60 views

3 digit of 7-segment on logisim

I'm working in a project, which will show an arithmetic result as a 7-segment, I know how to do a one digit 7- segment on logisim, but this makes the result limited from 0 to 9, and my project ...
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43 views

Why does my synchronous up counter count enable not function properly?

I have designed a simple 4-bit synchronous up-counter, using master/slave JK flip flops in Logisim. Here is my JK design: And my counter design: It works perfectly as intended, however if the INC (...
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38 views

How to use VHDL Entity in logisim evolution?

I'm new in Logisim and VHDL. I'm trying to use VHDL entity-component but the output always is "x". Then I read a document ( this link ) that said Logisim requires ModelSim to use this feature. So I ...
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32 views

Logisim Combinational circuit

Can someone please tell me why I am getting E for an output?
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1answer
53 views

Is A XNOR B logically equivalent to A XOR (NOT B)?

I am just wondering if its fair to say that A XNOR B is logically equivalent to A XOR ~B? If yes, how do I justify that without a truth table?
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51 views

Clearing 4-bit asynchronus counter using T flip-flops doesn't work

I am trying to make a BCD ripple counter that count from 0 to 9 , and I have watched a tutorial on YouTube , I implemented BCD counter as the instructor explained and after the counter reaches the ...
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62 views

3 Bit Adder Logic Circuit Design

Im trying to design a logic circuit for a 3 bit adder using 6 inputs, A2, A1, A0, B2, B1, B0 and 4 outputs, s0, s1, s2 and c (the carry out). I already have circuits for a half adder, full adder and a ...
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1answer
141 views

Displaying 6 bit numbers on two 7-segment displays

I designed 6 bit binary adder which should add two numbers in first complement. The numbers are being input via registers. I have to display the numbers and the result on two 7-segment displays via ...
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1answer
68 views

Counter Circuit starts from wrong number in Logisim

I'm trying to design a synchronous counter using J-K, T and D flip flop. It should count as "1, 3, 0, 2, 7" and 1 respectively. Everything works fine, i designed flip-flop tables and input-outputs ...
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40 views

Do these two memory register diagrams look correct?

So to start this off I have used J-K flip flops instead of D flip flops due to the equipment that I'll be using (Logic Tutor LT345 Mk2). The first diagram I am confident is correct but the 2nd diagram ...
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2answers
322 views

4-Bit ripple down counter using negative edge-triggered J-K flip flops

Ok, so as the title says im wanting to build a 4-bit ripple down counter on logisim so that I can find what 15 in binary is along with what 9 in binary is to make a mod-10 ripple down counter. But how ...
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1answer
126 views

4-bit memory serial to parallel memory register circuit question

I am building a 4-bit serial to parallel memory register and I feel like so far I have gotten things right, but I'm unsure of where to connect the CLR connections. Could someone have a look at my ...
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122 views

FSM in Logisim Evolution Using VHDL

I have been trying to make a state machine work in Logisim Evolution using VHLD. All the environment in Logisim has been set up and it's working for simple VHDL examples, so I can rule that out. The ...
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35 views

Logisim Flashing button

How can i create a button with a clock that is connected to a LED that the LED turns on when the button is pressed but even if you keep holding it it will turn off
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2answers
102 views

Designing a cryptographic S-Box in Logisim

I am currently working in Logisim and was wondering if I can design some ciphers in the same. One such cipher is PRESENT cipher which is essentially a block cipher. I did get that I need to design the ...
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1answer
118 views

How to get the IC numbers of the logisim items

Logisim makes it very easy for user to intuitively manipulate and edit the components already provided to achieve the circuit he wants. But there is no information ...
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1answer
92 views

Curious Behavior In Logisim while trying to mimic a halt instruction

I'm in the process of trying to simulate a halt instruction based on some arbitrary value. My circuit design may not follow best practices as I'm disabling the overall or master clock sign with a ...
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2answers
86 views

How to use two Demux to index a matrix layout of registers

Consider the following. Let's say for simplicity sake I have an arrangement of 8 bit registers in a 4x4 matrix layout. I could easily use a Demux that has a 4 bit input select line for the addresses ...
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1answer
106 views

Starting and stopping of a Mod N Counter for a FSM in Logisim

I'm working on a circuit for control logic. I'm using a 3 bit down counter. There is a control signal that when it goes high starts the counter by presetting it with a value of 5. The counter is ...
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1answer
89 views

Logism shows output as X, even though the gate is connected

Below is a basic not Gate using nandgate. Not Sure why output is X, when I change it to Output properties to three state no, I can't modify circuit. Some times, these issues go away when I restart ...
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2answers
237 views

Implementing a SN74LS245 Octal Bus Transceivers With 3-State Outputs in Logisim

I'm testing out different circuit simulator programs and I was able to build the integrated circuit SN74LS245 Octal Bus Transceiver in a program called Digital ...
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2answers
520 views

Help making a adder/subtractor on Logisim

I have attempted to make an 4 bit Adder and Subtractor circuit on Logisim, but i've came across a problem. So the Adder works but the subtractor doesn't. When i do subtraction the 1 thats carried in ...
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1answer
255 views

8-Bit Program Counter Implementation

I'm trying to construct an 8-Bit Program Counter, in Logisim. It currently has functions LOAD, which makes the 8-Bit input (A0-A7) appear at the output (S0-S7) on the clock pulse: Loading 1 as input: ...
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1answer
305 views

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
446 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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141 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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104 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
279 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
821 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
1k 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
122 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
699 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
361 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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2answers
750 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
2k 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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1answer
1k 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
229 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
126 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
275 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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1k 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
153 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
809 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
366 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
683 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
528 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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145 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
3k 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
713 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
982 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
774 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 ...