Digital electronics use a finite number of states, 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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find cache hit rate for direct mapped cache memory

I have this practice exam problem which I am having trouble with. I have gone over many slides but haven't been able to really get it. The question is I currently have an 8 block main memory with ...
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1answer
57 views

Circuit to Decrement by One

How to decrement a bit by one? I have A and 1 . I want the result to be 'A-1' . How to draw the circuit?
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2answers
56 views

Mixing multiple “boolean” audio signals

I want to mix up to 4 rectangle audio signals which come directly from a microcontroller's timer output pin and contain only one frequncy each. For example, if the microcontroller outputs 400Hz and ...
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0answers
27 views

circuit operation for error recovery circuit

in the figure sum1* is the partial sum generated from the adder of n bit and err_block[0] is the error signal which indicates error which is of 1 bit. so please explain the circuit operation for ...
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1answer
40 views

How can I build a 2 input AND gate 24VDC PNP inputs and 24VDC output?

I'm trying to build an AND gate that takes two inputs from standard 3 wire 24VDC PNP sensors and provides a 24VDC output. I was thinking using some sort of diode resistor logic (link to circuit: ...
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2answers
95 views

How to switch between two analog outputs with a digital output?

I have a circuit with a 74ls93 counter and I want to use one of its outputs to switch between two analog output, i.e., when the output of the counter is HIGH, the output of the circuit must be V1 and ...
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0answers
26 views

movement decision taken upon the light seen by a line follower robot

I'm working on a line follower robot and it has to check traffic lights every estimated distance and a decision of whether to move or wait is to be taken upon the current state's light of an external ...
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0answers
54 views

Is it possible to control the speed of DC motors with Arduino's analogWrite() using analog pins? [migrated]

I'm trying to control the speed of two DC motors that are connected to a dual H bridge. I always used digital PWM pins with analogWrite() to change the speed, but ...
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2answers
78 views

Why mosfet is preffered over voltage divider for voltage level shifting

Before writing this question I read several similar threads, but didn't found the answer I am looking for. When we need a voltage level shifter the first thing that come to the mind is a voltage ...
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1answer
54 views

how does RS flip flop works? [duplicate]

I am confused by this question for a long time. Let's say the initial states are R=1,S=0,Q=1,Q'=0, and both NOR gates are ideal (no propagation delay). Then both gates should change their states ...
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0answers
26 views

Using Optoisolator to Control a Toy

I'm trying to control Tweet Monkey (http://codefoster.com/tweetmonkey) using a optoisolator. It's a 816S, but it looks like the specs are identical to the more popular PC817. I have an Intel Edison on ...
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0answers
65 views

A general purpose 16-bit shift register

I cannot seem to locate a general purpose 16-bit serial-in parallel-out shift register that is still being made. Although there are plenty of LED drivers that can adapted for the purpose. All I need ...
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2answers
51 views

What is the wiring for a pull-down resistor on the Or gate?

Is this wiring and resistor the best choice as a pull-down resistor? Is it necessary to put the pull-down resistor(s) on all inputs and outputs? I put a 10K Ohm resistor connected to the chip ground. ...
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1answer
48 views

When untied inputs are necessary, what is the technology to use for an OR gate?

What is the best technology to implement for an OR gate when there will be an open input? I would prefer a common IC. I wired a quadruple 2 input positive OR gate, HD74LS32P. I have a PWM signal ...
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3answers
68 views

Digital Input Clamp Circuit Protection

To be able to connect some peripheral to digital input, I'm designing the circuit protection to avoid any possible failure due to over/under-voltage issue. So, I will add a clamp protection circuit. ...
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2answers
42 views

Design Priority Encoder using only NAND and NOR Gates

I'm trying to build an 8-to-3 priority encoder using only nand and nor gates. Below is a 4-2 priority encoder, however it is using only ands, ors, and nots. If I have specific activation levels (some ...
0
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1answer
47 views

Logic Level Shifter

I am trying to connect two devices on a PCB. One operates with 3.3V digital high and the other works with 5V digital high. I actually grouped the input and output pins (There is no bidirectional ...
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1answer
46 views

problem on logic 0 at 4027 ic

I have a circuit to generate simple sound with astable multivibrator and enable/disable it with j-k flip flop with reset pin, something like this pic: i have a problem with logic 0, when it occurs ...
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3answers
80 views

Analog power pins vs Digital power pins on chips

We usually have digital & analog power/voltage pins on our ICs. Analog power most probably for PLLs etc & Digital Power for Core. So, my questions are :- The different Analog & Digital ...
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1answer
41 views

IC to replace 4 FETs (switches)?

I have 4 data lines that I want to put to high-Z if a pin (let's call it EN_OUT) is high (or low, if necessary), otherwise connect through. I've successfully done that by putting an N-FET on each ...
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3answers
160 views

Divide-by-3 with square output?

I'm thinking of making an 8MHz about-square clock starting from a 24MHz about-square clock. All signals are CMOS with 3.3V(±10%) power. What are my options? I'd like it low-power, cheap and easy to ...
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2answers
74 views

TTL logic level , how NOT gate checks logic level ?

This is a TTL logic level checker circuit , highlighted blue area is a checker pin. Voltage at checker pin is 0.65V so this must be logic 0 , LOW LED will on. But in input of first 7404 NOT gate in ...
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1answer
51 views

3 - bit Counter (repeat after each 6 clocks)

I have tried to make a counter which counts until six clock cycles and then repeats. And would like to know whether I have done all right and the counter works correct. simulate this circuit ...
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1answer
34 views

Inclusion gate as universal gate

Assuming that logic 0 is available, show that the INCLUSION gate is a universal building block. I don't know what inclusion gate is.
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2answers
45 views

Shift registers in series

If we have for example 3x16bit shift registers connected in series, can we clock 48 bits of data through one shift register at once and then latch all of them to output data registers, LATCH CLK and ...
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2answers
51 views

Single input for consecutive state transitions in an FSM: preventing fall-through

Consider the following state diagram where the inputs are c and v. The system is also receiving a high frequency clock ...
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3answers
127 views

Computer peripherals to immediately (<5ms) detect digital input state change in C# programs

The C# application I'm working on needs to be able to be able to call a function within 5 milliseconds of a digital input signal's state change (0V = off, 5V = on). Rather than using software to ...
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2answers
56 views

how will i convert an if less than condition to hardware in digital?

i have a condition like if a number less than a constant ,then how can this be converted into hardware in digital design.Will this be converted into mux or something else?
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4answers
59 views

How to check if sync signal is inverted?

in input of a CPLD, I have a syncronization video signal that can be like this (positive polarity): or like this (negative polarity): I want to recognize the type of the sync signal and invert ...
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2answers
41 views

State diagram for JK-flip-flop

I'm trying to create a simple state-diagram for a JK flip-flop, and this is what I've come up with. I've seen other variants of this diagram, but to me this seems like a correct one if you look at ...
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1answer
45 views

Circuit controlling 6 leds

I want to build a circuit with logic gates and flip-flops, in each clock which will turn 6 LEDs in the following sequence: 1 - 6, 2 - 5, 3 - 4, 4 - 5, 4 - 6, 5 - 6, (repeat). I have spent 2 days in ...
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3answers
105 views

Can you use diodes instead of OR gate?

I am building a computer and thought if I could simply use diodes instead of OR gates. Will this work with logic ICs such as the 74LS, 74HC and 75HCT series? Sorry if this is a stupid question, I am ...
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1answer
26 views

Question about SR latches

I was just watching this video: https://www.youtube.com/watch?v=ti5jD7Q7BSA At 25:10, he says that if you have an active high SR latch with initial conditions S=R=0, Q=1, and you set S to 1, Q will ...
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25 views

XC7Z020 JTAG not connecting

In our design I am using a Xilinx XC7Z020 Zynq SoC. In some of the boards JTAG is not connecting, I have checked JTAG cables are working with other boards.
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2answers
90 views

Why we don't see adjustable “High” and “Low” Voltages for discrete logic gates

For single, discrete logic gate chips, why is it that we don't have adjustable types? The closest we have are those that vary along with voltage supply. I suppose it uses a voltage reference in the ...
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2answers
51 views

Boolean expression to 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 this: $$T = BD + \overline{A}B\overline{C} + ...
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1answer
41 views

Proteus VSM: digital vs analog resistor and LED

I'm a newbie to electricity and electronics in general. I've been reading about the principles and have a basic understanding of them. I'm also diving into creating my first basic circuits with ...
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2answers
65 views

Is this a 4:2 Multiplexor?

My instructor has been insisting that the multiplexor in the picture above is a 4:2 mux not a 4:1 mux and that my textbook (Digital Design and Computer Architecture by Harris) is incorrect and that ...
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1answer
71 views

Analog to digital conversion: are natural number values possible with an amplifier?

I drew this circuit up for a project in Multisim. The inputs for V1 are -0.25 to 0.25, and the outputs are 0v to 10v. When -0.25v is inputted the output should equal 0v. But its giving me an output ...
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1answer
78 views

What happens to the output of Optocoupler input voltage is negative

Here is an example of circuit using VIshay Optocoupler 4N25 5V to 3.3V GPIO Output (Inverted) Logic +5V Input ---> 0.0V output GPIO LOW +0V Input ---> 3.3V output GPIO High What happens to ...
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1answer
47 views

Need help converting 8 bit input into 3, 4 bit outputs

I have a midterm coming up on digital system design. My professor developed an ASM chart for a problem and I decided that I would try to fill out the code for practice. The simulation runs, it just ...
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1answer
29 views

drawing flipflop after statement table and kmap simplification

I try to make counter using flipflop. 15-0-1-2-8-7-5-13-6-9-15 synchronous counter using D flipflop Here is table: Kmap simplifications: After the steps, I don't know (what I do) how to draw ...
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9 views

radix 2 signed digit comparator

I am working on implementing a Radix 2 signed digit comparator as the one used in the paper of Olivares J. "SAD Computation based on online arithmetic for motion estimation" I have read his ...
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2answers
69 views

Mixing Assembly and C [closed]

Is it possible to use a mix of these 2? Using a pic4550 and mplabc18 Lets say i have a microcontroller, that in my port B (B0 B1 B2 B3 B4 B5 B6 B7) 1 Byte, I set it to a '00000001' Is it possible ...
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0answers
62 views

Need a Citation for Advantages of Lookup Table on Microcontroller

It is a known fact that lookup tables (LUT) are faster for implementing complex functions in digital logic and MCUs (as discussed here). I need to cite their advantages in a paper I am writing, for a ...
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20 views

Rise time degradation by connecting to an input buffer

Suppose I have an imaginary 1.8V lvcmos output buffer and I know from the datasheet that it has an unloaded 10-90 rise time of 1ns. Now I'm going to hook up 6" of trace, to an input buffer who has an ...
2
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1answer
48 views

fast(er) extend 8-bit mask to 16-bit for MCU

(Background/purpose: this is a far-out, ideal/overkill approach inspired by a project that handles ultrasonic sensors over bidirectional pins using an 8-channel input capture/output compare.) Using ...
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4answers
1k views

Avoiding confusion between no input and a zero in binary?

Suppose I'm transmitting data through FM where 0 is 2Hz and 1 is 4Hz. The transmitter is transmitting 2Hz when there is no input. If I fed the recieved binary to a UART port of a microcontroller, how ...
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2answers
65 views

How to design, build and test synchronous sequential circuits using D-Flip Flops?

I want to design, build and test synchronous sequential circuits by using D-Flip Flops. I know how to analyze state diagrams but I don't now how to obtain a state diagram using just outputs. P.S. : ...
3
votes
1answer
77 views

Poor clock output from Spartan6 FPGA

I am using the LX9 Microboard from AVNET with the Spartan 6 PFPGA. I implement SPI to read from an ADC (ADS7822). I was getting wrong sampled values. When I ched the signals with an oscilloscope, it ...