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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What are these Inputs on a 8-Bit synchronous forward/backward counter in Logisim?

Our instructor has given us this Counter and we were tasked with constructing a logic, which makes the counter go from 0 to 78, then from 78 to 0 and repeat. The Circuit you see works as intended when ...
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47 views

Digital downcounter not resetting

I have a digital down counter which is supposed to count from 9 to 0 and then it goes back to 9 (bottom) but it only goes back from 9 to 8 and then back to 9 and I don't understand how it works. Note ...
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108 views

Building a 2x8 memory using flip-flops and logic gates

The image represents a 4x3 memory.Build a 2x8 memory.
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16 views

Logisim MUX selection

I have designed a 4x1 MUX. I want to give the selection from two diferent inputs and not one 2bit input. How can I do that, if possible? In the image you see the "incompatible widths" error ...
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94 views

Apparently correct D-flipflop implementation breaking my circuit. When using built-in D-flipflop, the circuit operates correctly

I need to design a simple 4-way traffic controller for an assignment. Traffic is from Road 1, Road 2 and Road 3 (see diagram below). If there is traffic on road 1 only, road 1's traffic light stays ...
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26 views

Logisim Stopwatch w/ Date D/M/YYYY

I have a working stopwatch and I need to continue it so it will count up to 30 days, 12 months, and 9999 years but I am unsure of how to continue. Here is a picture of my logisim file:
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67 views

Why my register file operates abnormally

I tried to implement a 32x32 bit register file using Logisim, however once I have finished drawing and proceeded to test it by initializing the content of individuals registers to zero using the reset ...
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89 views

Logisim - Counter with clock and Magnitude Comparator not working as expected

I have the next circuit in logisim: It is a simple 8 bit counter, with a magnitude comparator that outputs 1 when certain value is met. The problem is that if I simulate with a clock, the counter ...
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86 views

Finite State Machine made of JK Flip Flops in Logisim help [closed]

I'm trying to make a 4 bit finite state machine that prints out (2, 3, 5, 7, 11) in order. I have completed the next state table, flip flop transition table and the JK Karnaugh maps for all the bits. ...
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181 views

Logisim Help - Using Custom D Flip Flop

I am trying to create a D Flip Flop to use in a bidirectional 4-bit shift register, using Logisim. However, when using my D flip flop the shift register acts just as a normal register setting the bit ...
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104 views

Why does this give me a red wire in Logisim?

Why does this gives me a red wire? Is it a bug? I'm pretty sure my wirings are correct.
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53 views

4 address lines for 1 bit input

I am currently trying to design a 16 nibble RAM on logisim, whereby it takes 4 data input lines. However, what I am having the most trouble with is converting the 4 address lines into a single input, ...
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87 views

Can I implement addition and subtraction in different operations using a MUX?

I'm building a 16-bit ALU that needs to be able to perform logical AND, OR, add, subtract and rotate one bit to the left. I need to have addition and subtraction operate with different op codes ...
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417 views

How do I implement a rotate left 1 bit operation in a 16-bit ALU in logisim

I'm creating a 16-bit ALU that has to perform logical AND, logical OR, addition, subtraction and rotate left one bit. I have everything working perfectly except the rotate left one bit. I think I need ...
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75 views

Convert from 4 bit binary number to 2 bit binary number

I am currently using logisim to output a 2 bit binary number, however, the bit adder releases 4 bit binary number instead. Is there any way to fix this? (I am currently using v 2.14.6 .)
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53 views

Counter with 4 flip flops jk synchronous from 1 to 12?

I wanted to create a circuit that would count from 1 to 12 to make hours counter for the digital clock. I work on logisim. I already made counter mod 13 but don't know how to adjust from 1 to 12 (not ...
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57 views

Simple ROM bit cell

I was reading about ROM example from Computation Structures. Here is the ROM example mentioned in the lecture. I set up a simple circuit to understand the inner working logic of the circuit. When I ...
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81 views

Connecting input and output to the same bus

I'm reading "But how do it know". And in register chapter, it talks about connecting both input and output pins to a bus. I tried to do it on Logisim but it shows red wires. Can someone ...
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42 views

Units, ten and hundred in a 7-segment display (LOGISIM)

I need to know how to represent in units, ten and hundred on a 7 segment display in logisim. I need to do a college job that is necessary to convert 8 bits from binary to BCD, from this a carry ...
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85 views

Logisim Evolution Oscillation Apparent With RAM

NOTE: I am using Logisim Evolution, not the original Logisim I created a simple subcircuit for a RAM chip in Logisim Evolution. It works perfectly fine unless I write to more than 1 at a time. It ...
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221 views

3 digit of 7-segment on logisim [closed]

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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1answer
81 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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337 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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50 views

Logisim Combinational circuit

Can someone please tell me why I am getting E for an output?
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486 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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96 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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177 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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490 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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278 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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45 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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943 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
307 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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95 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
132 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
308 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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170 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
172 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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231 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
212 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
493 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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3answers
1k 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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555 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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848 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
1k 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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180 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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182 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
423 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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1k 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
2k 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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130 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 ...