# Questions tagged [digital-logic]

Digital electronics treats discrete signals, unlike analog electronics that treat continuous signals. Digital logic is used to perform arithmetic operations with electric signals, and constitutes the base for building CPUs.

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### What is the proper way to implement hardware division when operand size is so much bigger than 16 or 32 bits?

Here is the equation that I need to implement in hardware. The parameters, r is 8 bit, s is 8 bit, d is 32 bit. The operation here is a division. Division in hardware is always a very difficult thing ...
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### Fan out of TTL Circuit

In this image When calculating the fan out of the TTL circuit the current in the TTL drive output is 16mA and is divided into the emitters of the load each emitter has 1.6mA because the fan out is 10. ...
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### Digital circuit that squares a 4-bit input

Many years ago, I found a digital circuit that squares a 4-bit input in an old textbook (perhaps 1970s or 1980s, possibly older). (The figure below is not the original figure. I think the figure ...
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### Chaser circuit with a chain of 4017's

I have a problem with this chaser circuit. It should work like this: When I switch on the power, no outputs should be activated. When I press the reset button, the clock signal will be started and ...
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### How to properly constrain ethernet phy

I am trying to use the ethernet PHY on my Nexys4-DDR. The manual for the phy gives the following timing constraints for the RMII ports. I am getting confused as to what exactly the constraints for ...
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### Circuit to Disable 24VDC to Load via +24VDC Logic Output

I have a load that is powered by a +24VDC source. The load can draw a max of 400mA. I would like a simple and effective circuit to disable power when a 0-24VDC logic signal is high; in addition, I ...
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### How to understand this combinational cyclic circuit made of interconnected SR latches?

I'm trying to understand the following circuit, or better said, what must be the approach to analyze other similar ones: What I'm doing for now is forget about the clock signal and the ...
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### Help to understand the operating logic of the Bosch charger

I ask for your help to: determine, if possible, the type of transistor T5, T7 (SMD code: MK3C). help me understand the operating role of the set T5, T7 and R23, R33 in the circuit (it's like a ...
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### The concept of DDR rank

I have an understanding of DDR rank which I think is incorrect. If someone could join the dots then there would be more clarity. Here is what I know A DDR rank is a 64bit interface consisting of x8 ...
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### 200 Input Smart Multimeter Project

First off, thanks for taking the time to read this and help out. Here's a quick overview of what I am trying to design. I have a break out box that has 200 female probe inputs. Each input is numbered, ...
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### karnaugh table issues

Hello,I have this truth table.I did this table and I am creating a demultiplexer 1 in 2.Not multiplexer. Second,I did and that I gave and those Am I right?I want to confirm that I have done it all ...
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### Johnson counter using structural modelling in verilog

I'm trying to build a 4 bit johnson counter using JK flip flops and structural modelling. For the FF's themselves I'm using behavioral code and then instantiating them inside the counter module which ...
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### Multi-level NAND circuit simple conversion

I am working on understanding the NAND conversion. I have just got the basics of two-level NAND conversion, and when I went to the book example for a multi-level NAND conversion it used solved an ...
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### How does the loopback on a non-retriggerable monostable work?

I understand how to connect a monstable multivibrator to be in the non-retriggerable mode. Just loopback the /Q to the falling edge input or the Q to the rising edge output) as in the following ...
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### How to read out a capacitive sensor, (CDC, CVC, TDC)?

What are the main principles for reading out a capacitive sensor? I read a lot, but I cant figure out what re the different options. I think that an option is to convert the capacitance into a ...
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### How to make a PLL output the phase modulo 360°?

I have made a PLL to obtain the mechanical angle encoded in quadrature sine signals (the envelope of a resolver output) ; it implements: error=in-out is approximatively equal to sin(in-out)=sin(in)cos(...
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### Making aysnchronous sequential circuits hazard free

The problem I am stuck at requires me design a hazard free asynchronous sequential circuit for a given problem description. I have followed the routine steps as follows: I have obtained the primitive ...
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### LVTTL signal splitter - delay - combine circuit

Pulsed laser driver provides NIM logic level output for synchronization at the laser repetition rate (20 MHz) https://www.nktphotonics.com/lasers-fibers/product/superk-evo-industrial-white-light-...
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### What's causing a master-slave JK flip flop to get 'stuck'?

I've built a JK master-slave flip flop according to the following schematic: Putting it into Logicly I have the following diagram: However, regardless of which switches I change, the final two NOR ...
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### Is it possible to use cascaded 1 bit magnitude comparators to create an n bit magnitude comparator?

I know it is possible to use 4 bit comparators to create N bit comparators as shown in this Data Sheet http://www.ti.com/lit/ds/symlink/sn54s85.pdf but is it possible to do it with 1 bit comparators?...
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### How to count the units moved with 2 motor encoders

I have a 2 wheel device that both has motor encoders, counting the units moved on both motors is simple if the both motors speed is the same. My problem arises when the device is turning to the left ...
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### Determine maximum length of repetitive sequence in synchronous FSM

I have the following realisation: The figure shows a synchronous circuit with the clock on Rising Edge. The circuit will generate a sequence of values on the output (abcde) of the five D-flip-flops. ...
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### MOSFET input and output capacitances

I need some explanations about the MOSFET parasitic capacitances. Precisely, what I studied is that there are those parasitic capacitances: But generally in digital electronics texts I see that they ...
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### Bipolar transistors that only connect via base to emitter

I am trying to understand how to use this configuration of the LTC2992 power measure IC and the only part I am confused with so far is the two transistors which I have circled. What I know so far ...
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### What is the least expensive way to build a three-bit shift register?

I'd like to build a queue of three internal bits as inexpensively as possible. Externally, the queue has two input bits and one output bit. The inputs are (dataIn) and (shift), and the output is (...
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### I’m having trouble solving this digital circuit. Help!

I need to design sequential logic circuit from this state diagram using only 2 D-latches. And this is my attempt: If I put it in the simulator it just gives me error and wont count. I assumed that ...
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### Digital Comparator from LSB to MSB using Lookahead

This is homework to be upfront, but I'm really stuck on it and just need some kind of direction. I've been assigned to create a 16-bit lookahead comparator going from LSB to MSB using no more than 4-...
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### Transition time (rise time) and propagation delay

Recently in class I have encountered the following calculation of the propagation delay of the following digital circuit: Could anyone please explain to me the addition of the rising time of X2 and C?...
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### Two different ways of writing the same thing but generating different behaviours in Verilog

I have a part of Verilog code that is basically trying to synthesize a flip-flop. I have been experimenting and it seems that I can come up with two ways of writing it. The first way being : ...
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### Semiconductor Level Genetic Programming

I was reading a most likely old article about, Adrian Thompsons work on using genetic programming to generate circuit solutions for simple tasks such as frequency differentiation. This got me ...
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### Digital dice counting from 1 to 6

check it out guys ]3]3 the circuits above are both for an electronic dice that is supposed to count from 1 to 6 but none of the LEDS are turning on for the one that is far below, can anyone tell me ...
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### Which serial protocol or encoding scheme does this scoreboard use?

I am trying to decode a signal stream coming from a Nevco scoreboard controller: Packets like this are sent every ~2.7 ms. I suspect it is some sort of UART signal because it is on the RX line of a ...
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### Constructing Excess 3 BCD to 7 segment decoder - circuit hints needed

I am currently trying to construct a circut for an Excess 3 BCD to 7 Segment decoder. Therefore the input range ranges from 0011 to 1100 in binary inclusive with the rest of the inputs being don't ...
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I am a bit stuck with the concept of carry-lookahead adder so I'd like to compare it with another concept I'm more familiar with: the ripple-carry adder. I'm trying to make some basic math comparison ...
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### Implementation of Distributed Arithmetic Architecture

im looking at implementing a distributed arithmetic architecture, but running into some trouble. From the textbook im looking at we can rewrite the unsigned convolution of two of two vectors ...
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### CORDIC module for (0, 90)

I found this CORDIC Verilog code online. It calculates sine and cosine from (0, 360). I was thinking if there is a way to modify it to (0, 90) and then use 4 such CORDIC modules in a pipelined ...
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### Is this a correct FSM graph?

This is question from H.ROOTH book Fundamentals of Logic Design. A sequential circuit has one input (X) and one output (Z). The circuit examines groups of four consecutive inputs and produces an ...
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### FPGA blocking assignments in always block not working properly

In the following setup I have created a custom clock through switch on Spartan 3E FPGA to toggle the LED states one by one. I have connected 8 registers with 8 LEDs. By triggering the clock through ...
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### Confusion In Fanout of Logic Circuit and Transistor

Fanout:-Maximum Gate we connect to output of any Logic gate. so there is limited number of gate we connect the output of Logic Gate.hence there is some minimum condition required for operation of ...
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### Digital input conditioning?

I'm designing a schematic with opto-coupled digital inputs (BNC). For better noise/ground loops immunity/reflections should I add 50 ohm resistors on both input lines, signal(+) and GND, along a ...
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### Clear D Flip Flop when FF input is not equal to 1

I am trying to implement magnitude comparators with storage as a D FF. In this picture, if X is equal to 0, second AND gate on magnitude comparator (that comparator in rectangle) will give 1, as Q' &...
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### Amplitude modulation on FPGA

I'm trying to implement amplitude modulation on a Xilinx Vivado using Verilog HDL, but can't seem to get the proper output. Can anyone point out what I am doing wrong? This is in reference to my last ...
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### How to determine if a gate/inverter can drive a fanout of 4 gates?

I have a circuit in which a driving inverter output (Fanout of 4) with equal Wn Wp sizing (m=4) is driving 4 other gates having same equal Wn Wp sizing (m=1). How to calculate if the inverter fanout ...
1 vote
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### How to convert data signal line coding from RZ to NRZ?

I have a user data stream at 10 kbps and line coded as uni-polar, 0-5 Volts, RZ (return to zero). What methods are there to convert this signal to an NRZ (non return to zero) format? The only way I ...
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### Discrete digital input

I have a homework question that mentions discrete inputs and I wanted to clear up some of my confusion on the topic. When looking at truth tables, as an example, would A and A' be two discrete inputs?
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### Why is the hold time given by the delay through the 3-input NAND gate in this D FF?

Consider the (somewhat optimized) implementation of a (positive edge-triggered) D flip-flop given in the attached image (which comes from the book by Brown and Vranesic). It is stated that the setup ...
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### Understanding Forwarding unit

I am new to this subject and am having trouble understanding this topic. Suppose I have the following circuit to control the forwarding of a MIPS pipeline processor: So the forwarding control will be ...
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### DDR interfacing with rockers3399 processor

I am using rockers 3399 processor in one of my applications. if you see page no 9 'External Memory or Storage device' section you can see the below things *Support 2 channels, each channel is 16 or ...
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### If two Boolean functions $f_1$ and $f_2$ have same truth table, does that means they have exactly same characteristic? can one f1 numerate to f2?
if $f_1(x,y,z)=\neg xz+x\neg y+\neg xy\neg z+xy\neg z$ determine if $f_1$ is symmetric and whether it is unate. What I thought is: $f_1$=¬xz+x¬y+y¬z, the truth table of $f_1$ has the same ...