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Questions tagged [digital-logic]

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

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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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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 below ...
JRN's user avatar
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Erratic and confusing I2C behavior between ATSAMD21G18 and A89307 through ISO1644 isolator

I'm working on a BLDC driver using Allegro's A89307 controlled by an isolated ATSAMD21G18 via TI's ISO1644 I2C digital isolator. The simplified I2C connection is shown below, I omitted all the bypass ...
Jess S.'s user avatar
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2 answers
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What is meant by TTL in this context?

Regarding this driver manual, the analog input has range 0-5 V with 1 MΩ input impedance. But the manual also writes that the analog input is not TTL compatible: I thought the term "TTL ...
GNZ's user avatar
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LM311 comparator not working as expected

I am attempting to recreate the 'cheap SPAD' experiment detailed here, which uses reversed LEDs as Single-Photon Avalanche Detectors. However I am running into a persistent issue when it comes to ...
Sanskar Jain's user avatar
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208 views

CD player playing digital noise on a track full of silence

I'm trying to repair a Nakamichi CD Player 3 that I got recently. Service manual from ElektroTanya Relevant section of the schematic: Initially, it would not open and just show an error. Replacing ...
akasaka's user avatar
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Need help to identify an unmarked SOT23-5 IC

I have come across a PCB which is a vibration sensor (switch) based motion detection logic, where on any vibration is detected, the circuit will turn on/off a load. It works in same way as a Push ...
Sathish V's user avatar
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Is there any reference to design a 4*4 bit ram only using transistors

I'm currently doing a project and would like some help. I need to create a 4-bit 4-word RAM using PSPICE. (I'm both new to the PSPICE program and new to the topic of RAM) I currently have successfully ...
Alan Gabriel Reyes's user avatar
3 votes
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320 views

Minimalist 3-input XOR gate using CMOS

As an enthusiastic noob to CMOS I browsed multiple examples of XOR gates using PMOS and NMOS. I find it hard to find any good examples of 3-input XOR gates; I found an example of a 4 FET 2-input XOR ...
David H Parry's user avatar
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Why does NOR need one more output to the multiplexor but NAND not in ALU?

Recently, I was learning "Computer Organization and Design: The Hardware/ Software Interface" riscv 2nd Edition by "David A. Patterson" In appendix A, A-37 shows the question in &...
An5Drama's user avatar
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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 ...
maher471's user avatar
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276 views

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. ...
Ahmed Redwan's user avatar
3 votes
1 answer
109 views

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 ...
Erwin's user avatar
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Why input combinations producing output '1' constitute a standard SOP expression and those producing output '0' constitute a standard POS expression?

Why input combinations producing output '1' are picked for forming a standard SOP (Sum of Products) expression and input combinations producing output '0' are picked for forming standard POS (Product ...
user8379230's user avatar
3 votes
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468 views

VHDL: Booth's multiplication algorithm process block not working as intended?

I am trying to implement Booth's multiplication algorithm using this flowchart in VHDL. So far, I have written the code below: ...
First User's user avatar
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How to ramp a bi-polar Return to Zero (RZ) digital waveform

I am using a Raspberry Pi Pico and a few op-amps and resistors to implement an ARINC 429 transmitter. ARINC 429 is a bipolar RZ serial communication protocol commonly used in avionics. See the image ...
ViperJuice's user avatar
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Z80 interfacing, address decoding logic produces noisy signals

I really would like to have suggestions and feedback from someone. It's about digital logic, in detail, the Z80 interfacing. In this design, I used a 74HC30 which is a 8-input NAND Gate. I'm using it ...
ozw1z5rd's user avatar
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Misunderstanding in sequential and combinational implementation, based on blocking or non-blocking behaviour

I have a very simple module that waits for the valid signal to become 1 and then sets the ...
Saeed Jazaeri's user avatar
2 votes
1 answer
65 views

Reason for the degraded I2S signal

I'm working with one of the devices from the NXP's IMX family - the IMX93 evaluation board. I've managed to setup the sound card drivers already, the next step was to test I2S signals output via the ...
Antoni's user avatar
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Gating LED monitor backlight at 16 kHz

I'm trying to make a circuit to flicker the LED backlight of an LCD computer screen using a TTL pulse at approximately 16 kHz - the aim is to avoid it interfering with a microscopy system by turning ...
Adran's user avatar
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Toshiba T2204A Air recirculation solenoid controller

please help me sorting out the pinout of the Toshiba T2204A. I spent more than a week of googling for datasheet, however the closest I could found is a similar package 2SK150A. I'm unsure this could ...
Jaki's user avatar
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1 answer
471 views

Program counter updating in a single-cycle ARM processor

This picture is from the book Digital Design and Computer Architecture: ARM Edition. It implements the LDR instruction. I have one question: R15 is supposed to be PC+8. In the picture, is R15 ...
user394334's user avatar
2 votes
0 answers
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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 ...
BobLamb's user avatar
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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 ...
gobears21's user avatar
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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 ...
Martel's user avatar
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2 votes
1 answer
72 views

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, ...
bmilesyo's user avatar
2 votes
1 answer
69 views

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 ...
ek.Nik's user avatar
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111 views

Randomly Floating PWM signal

I am having trouble with a randomly floating digital signal. Transmission is between a microprocessor and a CPLD unit and is used to run a half bridge. Measurement was taken after the output resistor ...
Julez's user avatar
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1 answer
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Is this state machine correct for a Mealy 4b'1001 sequence detector?

Is this a correct state machine diagram for detecting the 4-bit sequence 4b'1001 using a non-overlapping Mealy FSM? If any bit is out of sequence, reset to the initial state. Once the last bit of the ...
mansarogue's user avatar
2 votes
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330 views

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 ...
Francis Poirier's user avatar
2 votes
0 answers
89 views

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 ...
user252265's user avatar
2 votes
0 answers
471 views

Inferring a pipelined divider in Verilog

I want to synthesize an integer divider in Verilog to divide 16-bit integers by 8-bit integers. I assume that the compiler will be way more clever than me when it comes to implementing the details of ...
John M's user avatar
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101 views

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(...
Mister Mystère's user avatar
2 votes
0 answers
68 views

Making aysnchronous sequential circuits hazard free

The problem I am stuck with 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 ...
Archisman Pathak's user avatar
2 votes
0 answers
195 views

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-...
bl8zr's user avatar
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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 ...
David542's user avatar
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1 answer
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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?...
millocorona's user avatar
2 votes
1 answer
36 views

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 ...
Jake quin's user avatar
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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. ...
Carl's user avatar
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2 votes
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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 ...
trak's user avatar
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1 answer
100 views

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 (...
KevinSim's user avatar
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436 views

Voltage Across NMOS and PMOS Transistors

So I have the question above concerning an NMOS and PMOS transistor. The goal is to find V1 and V2 in steady state. My understanding is that because the gate voltages of zero and Vdd are there, the ...
brc1010's user avatar
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2 votes
0 answers
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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 ...
Dangz1's user avatar
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0 answers
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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-...
Lucas Wetherall's user avatar
2 votes
0 answers
254 views

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 : ...
ironstein's user avatar
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2 votes
0 answers
464 views

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 ...
user3880651's user avatar
2 votes
0 answers
662 views

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 ...
xyk2's user avatar
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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 ...
user38041's user avatar
2 votes
0 answers
2k views

How to compare carry-lookahead and ripple-carry adders?

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 ...
Giuseppe Crinò's user avatar
2 votes
1 answer
131 views

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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