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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43 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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46 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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1answer
46 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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1answer
349 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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64 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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47 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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1answer
46 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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2answers
47 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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38 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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47 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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1answer
101 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
55 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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142 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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40 views
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289 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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1answer
56 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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1answer
110 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
241 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
134 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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42 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
535 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
228 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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158 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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1answer
50 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
119 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
185 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
124 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
119 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
142 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
133 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
336 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
728 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
386 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
530 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
669 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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148 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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143 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
304 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
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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2answers
127 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
743 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
450 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
1k 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
2k 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
250 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
143 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
328 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 ...
