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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23 views

Different frequencies of digital signals over long distance

I am working on a solution which will need to transport some different frequencies of digital signals over 10-20 meters. I have worked out a design with the following components: PCB with An ESP32 ...
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30 views

Diode ROM with decoder and multiplexers

I have this question on my exam I couldn't answer: A diode ROM has been built using a decoder and multiplexers. If A4A3A2A1A0 = 01001, what is D3D2D1D0? Here is the first schematic: The answer is ...
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35 views

CD4006 Behavioral model in LTSpice

I want to simulate the behavioral model of CD4006 chip in LTspice. It is a CMOS 18-Stage Static Register. Looking at the Datasheet I see the one stage logic diagram that consist of inverting buffers ...
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44 views

Is the TC (“terminal count”) output of a 4-bit sync counter (74163) reasonably assumed to be glitch-free?

My gut tells me so, but the proof eludes me. Effectively this output is the AND of all four bits. These four bits go from 0 to 1 at very distinct times, assuming the counter is running at a ...
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80 views

Design a sequence detector to detect 1001 or 11

I want to draw a state diagram about the sequence detector circuit. The circuit will generate a logic “1” output is a sequence of 11 or 1001 is received. I have my answer, but I don't know my answer ...
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39 views

Functionality of the circuit

I made the timing diagram for this circuit, but i am not sure if it is correct. Please confirm my timing diagram and what is the functionality of this circuit? Is it to generate a pulse 5 clock cycles?...
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What is a Logic diagram? [on hold]

I have a task that tell me about the logic diagram of the equation "L=A+D¬X" in digital logic desigb
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65 views

Operation of this circuit

I have this circuit. I did the truth table but I wasn't able to understand what operations this circuit do on pair of 2-bit binary inputs (A1, A0) and (B1, B0). I thought it was mod or div but it's ...
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47 views

Driving LEDs with open collector outputs for Tally system

I thought it best be start with some context. We're trying to connect two "Tally" systems together - system that turns on a red or green light when a camera in a studio is live or on standby. The ...
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80 views

FETs or NPN transistors open at 0V at base in CircuitLab or is something wrong with my circuit?

I came across what look like a bug in CircuitLab, but I am not sure. There is a good chance that I am knowledgeable only to be dangerous. In the context of How to make a 7 to 3 priority encoder? I ...
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48 views

How to prove identities of a boolean equation?

I have a equation which I'm trying to solve but stuck at a point. $$(a + b).(\bar{a}.\bar{c} + c).(\overline{\bar{b} + ac}) = \bar{a}.b$$ This is what I've tried so far, $$(a + b).((\bar{a} + c).(...
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66 views

Realize using NOR gates only?

I came across a question regarding logic gates and I can't understand how to solve it. Q) Construct the truth table and write the boolean output equation. i) Realize using NOR gates only: $$f(A,B,...
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64 views

VOH is lower than VIH

I have a SoC connects to a DSP with SPI. They are all powered by 1.8V, so I didn't even compare SoC's Voh and DSP's Vih at the first time, they should working fine. However, yesterday my colleague ...
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45 views

Combining 2 NOT / BUFFER gate outputs for same input to increase current output

To drive a RLC circuit by pulsing at a frequency close to 1MHz, I would like to use a schmitt trigger inverter gate (SN74AC14) / buffer (SN74LVC2G17) in between the uC pin and RLC circuit for higher ...
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75 views

Clock frequency divider circuit (divide by 2) using D flip flop

I was trying to implement frequency divider by 2 using D flip flop with the logic connection of ~Q to D input. I provide 2x clock frequency of 50% Duty cycle in the hardware where D flip flop is made ...
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40 views

Group multiplexer

I've got a project on my Digital Electronics course and I'm stuck. I've got five 7bit sources which I want to choose from by counter and multiplexer. But multiplexer has only one bit inputs and output ...
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289 views

A newbie question about the function of tri-state output?

I'm trying to understand what is the use of tri-state output and what is the advantage of using it. Below depicts both two-state and tri-state output: According to the above logic, it seems to me ...
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73 views

Logic DIP switch console breadboard

I want to use a single breadboard slice to build a console for a mini-computer project. It will have 28 or more parallel control and data lines, each with the following features: state indicator LED ...
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2answers
84 views

Logic Implementation

I need to implement a circuit but Im having some trouble since Im novice on electronics. I have 4 inputs. A being ON/OFF switch. B is an Inibitor. C is an Emergency and D is not an adequate ocasion. ...
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80 views

Design this memory with D Flip-Flops

Design the following memory with D Flip-Flops. (you can use other gates or decoder if needed) The following memory has 4 one-bit locations and can access 2 locations in each moment and read from ...
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32 views

Fast Arbiters for On-Chip Network Switches

For "Fast Arbiters for On-Chip Network Switches", what is the difference between Proposed-I and Proposed-II topologies?
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22 views

Mod - 7 Asynchronous/Ripple Down Counter Using J - K negative edge triggered Flip-Flop

I was trying to build the mod-7 asynchronous down counter from negative edge triggered JK flip flops. I am stuck as to how to start with 110 after 000 in the sequence. A circuit diagram related to ...
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1answer
43 views

Are there combo gates XOR followed by AND? (4-bit identity comparator)

Is there no 4 bit identity comparator in TTL or CMOS? It could fit into a DIP-12 package as all it would have is 4 XOR gates for selectable invesion and 1 4-way AND gate. OUT := (A1 xor B1) and (A2 ...
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Triggering the Adafruit Audio FX Board

There exist these little wav trigger boards There are some (11 I think) sample trigger pins on the board which are active low. So generally you're expected to connect them to ground via a momentary ...
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43 views

Understanding Common mode voltage

I am trying to understand common mode voltage a little bit fundamentally (only with electronic devices and no math). I watched this Youtube Video to understand common mode and differential mode ...
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81 views

Can Vias be used on the board for branching tracks?

I need to split the RST line in two directions and also connect it to the opposite layer of the board. I did it like this: Is branching the RST line the right decision?
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37 views

Avoiding shorts when switching between bus lines with a mechanical switch

I've designed a circuit to choose between two 8-bit digital buses. I'm taking advantage of the fact that the 74AC540/541 chips have tristate outputs, so can enter into high impedance state to allow ...
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34 views

Switching between sequence different sequence lengths in pseudorandom number generating

I was reading Use Readily Available Components to Generate Pseudo-Random Binary Sequences and White Noise, by Art Pini, to understand generating pseudorandom numbers. I understand that broadly ...
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1answer
88 views

How to generate 2's complement of a 3-bit number using 3:8 active low decoder?

This is previous year problem of a competitive exam. I tried by self but i was unable to solve it. Exact wordings of the problem: Generate 2’s complement of a 3-bit number (a2a1a0) using a single ...
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78 views

Why do we use diodes when we connect a 7414 IC?

I was looking at a lab in Digital Circuits and there was a questions: Why do we use diodes 1N914 in the circuit in figure? What type of input signal to the circuit would make the diodes unnecessary? ...
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Same circuit for Multiple Asynchronous PRESETs / CLEARs

I'm using a dual JK flip flop (IC 74109) in my circuit. I want to keep one of the two flip flops cleared initially, and want to preset the other.So, I intend to use the asynchronous preset and clear ...
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Confusion about GND and PGND

In a digital circuit like a cell phone. If a switching ic has it’s reference point as PGND, separate from the main GND (4v Main vcc coming from battery), but they’re tied together, then What exactly ...
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54 views

Is this way proper to create differential inputs from a function generator for this setup?

I have soldered an RS485 to TTL converter on a board and want to test it. The thing for a test, I need differential inputs as DATA+ and DATA- and I don't have a sensor which outputs differential ...
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22 views

How to use one H-bridge to control multiple latching solenoid irrigation valves?

I'm using Arduino Uno to operate a latching solenoid irrigation valve by using an H-Bridge to set the polarity of the 12V DC going to the valve. A 500 ms + pulse on a digital output pin turns the ...
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27 views

Audio codec output detection

I am looking for guidance on audio functionality test over USB audio codec. This audio output serves as Alarm to indicate certain events. The signal flow is ARM processor USB port --> USB Codec --> ...
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28 views

Logism wire error on AND gates

I recently started working with logism and am doing a small basic project designing a circuit using it. I've built one of the subcircuits and made my "Error" subcircuit output a constant 0 for now. I ...
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87 views

simple way to invert logic

I need to feed a pair of logic inputs of a DG211 electronic switch with a single logic output from my 3.3V microcontroller. The two logic inputs on the DG211 need to be one the opposite of the other. ...
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37 views

Logical level conversion with MOSFET-N

I doubt if the way I am converting the logical level is correct and if it is the best way to do this. The PWM_1 signal comes from a STM32F4 microcontroller. When PWM_1 = logic level 1 I have 3.3V. ...
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55 views

How do you fix the glitches in the following Karnaugh maps?

The following circuit is supposed to output 1 if the input is greater or equal than 1010 (decimal 10). The truth table is given and we are supposed to convert that to POS and SOP using Karnaugh maps. ...
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Why does the output of NOT gate (in a 74LS04 IC) equal to one when the input wire is not connected to anywhere?

I have a 74LS04 integrated circuit, like this: source I put this IC on a Bread Board and connect the negative and positive parts of the Bread Board to negative ...
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41 views

Understanding complements on inputs

I've got a problem understanding formal writing down of complements on inputs. During my laboratory exercise I was working with a device that had D flip flop embedded in it. The goal was to ...
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63 views

What's wrong with my timing diagram?

I have made this simple timing diagram that presents the triggering way of D flip flop. The flip flop is triggered by clock's rising edges. I am convinced that the diagram is correct signal-wise. ...
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441 views

Is a ground connection needed in between master and slave for this RS485/422 scenario?

I will work on a small project where an SSI-output data (angle data) of a rotary-encoder will be read by a micro-controller board (such as an Arduino board) and the micro-controller will then send ...
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83 views

Raw programming of an Altera FPGA

I have an Altera Cyclone IV FPGA (for ie) and my question is: is it possible a raw programming of the FPGA? Is it possible to set "manually" the gates for making experiments? Thank you
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65 views

When should we NOT simplify a digital signal in an expression?

When we do a simplification in a Boolean expression, sometimes we eradicate some Boolean variables, either from part of the expression or entirely if it's not needed. Is there a case in digital design ...
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Is it better to combine logic for two flip flops in a single always block?

I have always used separate always block for infering different flip flops when they dont have much in common. ...
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187 views

Is this circuit from a textbook wrong?

(This is not a homework question.) While reading "Digital Computer Electronics" by Albert P. Malvino, I found this circuit on page 121, figure 8-22(a). It claims to be an example of a discrete TTL ...
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Can the output of one logic gate serve as input to more than one subsequent logic gates?

NOT gates take one input, AND and OR gates take two inputs. But can any gate have more than one output? I've only ever seen diagrams where each logic gate has exactly one line coming out the right end....
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Symmetric Inverter Sizing Based on load capacitance and propagation delay

I am doing Symmetric Inverter Sizing Based on load capacitance and propagation delay that is given. Also mobilities, threshold voltages are given. Symmetry ratio is process dependent based on ...
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2answers
63 views

2-Bit timer with 1 ms period

I am trying to find a simple hardware solution to implement a 2-bit timer that gives out 2-bits continuously repeating data 00, 01, 10, 11, 00, 01.... whose time period is approx 1ms. The accuracy and ...