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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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Creating or Gate using Mux [on hold]

I need to process the function Z=x+y on a multiplexer. Is either of my solutions correct?
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31 views

Iterative CORDIC algorithm dynamic shift optimization

I've implemented the CORDIC algorithm on an FPGA using an iterative approach. The component is loaded with a set of values to calculate and then iterates as many CORDIC steps as necessary for the ...
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2answers
37 views

How to send a digital signal when analog sensor (QRE1113) reaches a threshold value without resorting to wasting analog input pin?

I'm building a miniature pinball machine and I am attempting to use an infrared reflector sensor (QRE1113) to detect when the ball rolls over it (I got the original idea from Ben Heck's videos). In ...
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2answers
65 views

Device that transmits signal to computer [on hold]

How would I be able to send a notification or email/msg of some sort to my computer after an event has taken place from elsewhere. To be more specific, when a tripwire is tripped, (LDR/Laser beam) how ...
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27 views

Two bit upcounter moore

I am to construct the state machine for a Moore two-bit up-counter with a synchronous reset. Output is 1 if the current count is 0, (state 00). Binary upcount if x=0 and in Gray if x=1. My attempt: ...
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40 views

Binary multiplyer by 8

How can I design a circuit that take 3 inputs lines and multiplies these inputs by 8 using only 4 bit full adder ?
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34 views

Implementing a circuit that takes a 3-bit number and multiplies it by 8 using only 1 4-bit adder

I was solving a past exam and this question popped up and nobody seemed to agree on an answer. Someone suggested this solution which is just hacking your way to the required result. That suggested ...
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27 views

Design sequential circuit with 3 state buffer

I asked to design a sequential circuit with 3 state buffer so when : Load = 1 -> put data into output Load = 0 -> don't change output Here is my design: But question said also use other gates. Is ...
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2answers
76 views

Ferrite bead for high-speed digital IC

Although I've seen numerous recommendations for the use of FBs on the power supply rails of noise-sensitive analog circuitry, the opinions regarding their use with high-speed digital circuitry are ...
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1answer
42 views

Multiple Reset Synchronization

I have two active low async resets (rst_na and rst_nb) and associated two clocks (clk_a and clk_b). Assume Block B required ...
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31 views

110v AC “Low voltage LED lights dimmer” controlled with DC 3V3 [closed]

I'm new to Electrical Engineering and this is a hobby for me, appologies in advance if this is a dumb question. I want to control a 110v LED lights that are dimmable. I already have in place sa ...
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2answers
62 views

compact fluorescent lamp noise on digital signals

The answers to this question about CFLs (compact fluorescent lights) in an electronics lab indicate there is some concern about the presence of electronic ballasts and CFLs in connection to radio and ...
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30 views

simulating inside circuit IC 74LS73 [closed]

I tried to simulate the inside circuit of IC 74LS73, but I get constant output. Has anyone ever tried it yet? I get 0 for Q and 1 for Q'. I tried it with quartus and proteus, but not with coding. ...
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2answers
24 views

Output Register and pipeline implementation

In his book "Finite State Machines in Hardware: Theory and Design (with VHDL and SystemVerilog)" the author said : 'The optional output register can be used to obtain a fully pipelined implementation ...
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77 views

UART RX in VHDL

I have to set up a UART transmitter and receiver using a Spartan 3 board. I've got the transmitter set up already and verified it with the arduino terminal using this FTDI breakout.The receiver is ...
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1answer
69 views

What is the name of this logic circuit?

Sorry for dumb question, I'm really newbie in electronic. As I wrote in topic, What's the name of this circuit? Dose the circuit has any specific name at all ?
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74 views

Making LED flash from steady-state signal

I am looking to design a simple circuit that detect objects placed in a spot. So far, the circuit uses simple IR LED and photodiode to detect the object placed between them. The voltage developed in ...
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1answer
80 views

Why VOH > VIH and VOL < VIL?

Electrical characteristics of any IC include VOH, VOL, VIH, and VIL. To interface any two ICs, VOH and VIH should be compatible. I am not able to understand why VOH should be greater than VIH and why ...
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1answer
93 views

Why is this considered a slow logic level shifter?

I'm working on a project where I have to do some unidirectional logic level shifting. I'm not able to get any chip to do it at this moment (it's late at night) so I looked up some DIY solutions and ...
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1answer
56 views

What effect does a logic analyzer probe have on a circuit?

I have an MCU controlling a LED sign. This sign speaks the HUB75 protocol, which is essentially a large shift register. Being a shift register, this requires a clock signal to be generated, which the ...
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1answer
68 views

What would the maximum current draw for this chip be?

I am looking at using this logic switch in my circuit: https://www.onsemi.com/pub/Collateral/FSTD16211-D.pdf Looking at the datasheet I am finding it hard to figure out what the maximum current draw ...
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2answers
368 views

Logic-level converter FET

I have been using the BSS138 level converter circuit for a while now and today it struck me I get how the voltage is stepped up by the FET or the BSS138 when you are applying say 3.3 V on the LV side. ...
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1answer
31 views

D Latch Design and Implementation

I have a digital signal called FAULT that is active-low. It will be high 99% of the time and low in rare cases. I'm trying to use a latch so that the majority of the time the output of my latch will ...
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2answers
42 views

A precision industrial measurement system uses a transducer that produces an output analogue signal of 5V peak, [closed]

A precision industrial measurement system uses a transducer that produces an output analogue signal of 5V peak, which is bandlimited at 2.5 kHz. The signal is digitized with an accuracy of +-0.0025% ...
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4answers
79 views

How to write this boolean expression using only NOR gates?

I'm having some trouble understanding how I can convert a boolean expression to a NOR-gate only expression. What I'm working with looks like \$T = A B' C + A' B C' + A B\$. How would I go into ...
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2answers
37 views

Digital control of contactors

We are trying to control a bunch of 3 phase contactors using an HMI. The contactors' coils are activated by two lines of the 240V 3 phase source (L1 and L2). We are trying to figure out if the ...
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2answers
101 views

Designing a RAM, using 4x2 chips, with a 8 address capacity

This is a typical exam question, and I've seen some very helpful posts about, but I still have a lot of doubts. Given an integrated circuit of certain dimensions, for this example a 4x2, I have to ...
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1answer
35 views

Optical receiver output voltage higher than power supply

The part is a optical receiver from Broadcom. It has TTL output, but specified with a maximum output-high voltage higher than the power supply. I wonder what's special structure internal may make it ...
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1answer
26 views

Understanding CMOS Circuit Behaviour with Resistive Loads using Thevenin theorem

I have been reading the Digital Design: Principles and Practices 3rd Edition as a hobby. Unfortunately, I am stuck at page 103 of Section 3.5.2: Circuit Behavior with Resistive Loads. In Figure 3-27: ...
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4answers
111 views

Need Help With Transistor Logic Circuit Design

Greetings all and Happy New Year! I've been working on a logic circuit to control the main entrance gate at our ranch for some time now. I've been testing using Falstad's Circuit Simulator. ...
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28 views

trigger a circuit using one time signal

I'm really new to electronics and I need help. Say I have Line A. I need to control Line A to set it as HIGH or LOW using a one time signal through one input line X or maximum through two lines X and ...
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1answer
30 views

Arbitrary Sequence Counter Up/Down

I've been having problems with one particular exercise at Digital Logic Design. I can't quite put my finger on it and i can't figure out why. I have to design a up/down counter on a given sequence. ...
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1answer
284 views

Designing a sequence detector(0110)

I asked to design a sequence detector to detect 0110 and when this sequence happend turn it's output to 1 for 2 clock cycles. Here is what I designed: But the problem is it turns the output to 1, ...
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1answer
97 views

What is going on with this zig-zag trace connected to the processor?

I'm taking apart a Pogoplug_V4_A1_V3.1, and I noticed this trace in a corner of a board, connected to the Marvell 88F6192 processor: The trace itself is approx. 0.2Ω, and the resistor is approx. 0Ω. ...
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2answers
108 views

Why do we need a chain of resistors to increase the voltage? [closed]

I did a workshop on SMT today and we made this board attached. However, what I don’t understand completely is the logic: why do we need 3 resistors to increase the voltage (on the boost part)? What do ...
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1answer
17 views

SNM (Static Noise Margin) and DNM (Dynamic Noise Margin) confusion in digital circuits

I've found in several sites that SNM is the min between NMH and NML where NMH=VOHmin-VIHmin and NML=VILmax -VOLmax But this paper really confuses me, because it uses the same graphics and apparently ...
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1answer
55 views

Logic Design simple door security system with using MUX

I draw the cicuit without using any MUX. But my project says I need to use 4x1 MUXs and I couldn't find where to use 4x1 MUXs. I tried put MUX of each output but this was very pointless, no need to ...
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1answer
46 views

Verilog nested for loop not behaving as expected

I am having trouble with a simulation of an 8-bit full adder i wrote in verilog. Basically I have two integers that I feed into the full adder, I add them together and I check if the result is as ...
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3answers
84 views

Latch-Up in CMOS-Devices

I recently read something about the latch-up effect in CMOS-Structures but I don't understand why are MOSFETs affected by this effect. I understand that high currents through the source-drain path ...
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1answer
50 views

Moore and mealy machine equivalence

I have come up with a problem which wants to convert a Mealy machine to a Moore machine. I searched the web and found out how to convert a Mealy machine to Moore machine and vice versa, but I have ...
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0answers
51 views

What is the procedure to use ISCAS-85 benchmark Circuits for testing? [duplicate]

Could you please explain the detailed procedure about using ISCAS-85 benchmark Circuits for testing available at the below link http://web.eecs.umich.edu/~jhayes/iscas.restore/ How do we start, could ...
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0answers
40 views

LEDS on Traffic Circuit using 555 Timer Don't Light up

Here is a picture of the circuit and circuit we built on the breadboard. We used every component as instructed and built it as such. The Green LED lights up for about 7 seven seconds then turns off, ...
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2answers
105 views

A circuit to convert 4-bit Gray numbers to BCD

I'm sorry for asking this specific question here but can some one please tell me what's wrong with this solution. Question: design a circuit to convert 4bit Gray numbers to BCD I have to say I ...
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21 views

Do not match upcoming states in Logisim project

Do not match upcoming states in Logisim. Any idea how can I solve this? This is the table of transitions: I do not know why the future states are always equal to the present states.
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24 views

Switching between multiple lanes to measure resistance

So I have a fair bit of MXM GPUs that have some sort of board problem or another, and measuring each pin vs ground is usually the second step to attempt repair. Oddly, I have an idea to measure ...
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1answer
45 views

Paralleling LVPECL outputs?

I have a pretty unusual application here, where I need to drive a fast differential signal fanning out into 8+ 100ohm transmission lines. The unusual part is this: the transmission lines must be ...
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1answer
69 views

D Flip Flop Toggle — Q into Hex Inverter into D, Unstable Output, Help

simulate this circuit – Schematic created using CircuitLab I created the above circuit. There is essentially a switch that is normally high. I press a button. Using a NTE4049T hex inverter, ...
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1answer
38 views

Is my truth table right?

I make a truth table for this question is it right??
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0answers
44 views

How to stop summing counter at exact value?

I want to stop summing counter at 25 decimal or 19(hex output) value while it's begin summing from 1 to 31(1F in hex).So how can I make it ?
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1answer
66 views

Rising/Falling Edge Detection for interrupt generation circuit issues

I am trying to generate a pulse to trigger an interrupt when the input changes state. High->Low & Low->High The input is a reed switch. I'm using a XOR gate (SN74AHC1G86QDBVRQ1) with an RC ...