# Tag Info

24

Possible reasons: Load Balancing The driver of A has an unknown number of fan-out to drive. Fan-out within the circuit and the parasitic it induces can be calculated for the specific circuits, but we do not know the other circuits that are connected the driver. Essentially the inverters are being used as buffer equivalent. and help manage the parasitic. ...

12

These "hardware addressing" pins are not for addressing words in the RAM, but rather to select the address of the whole device on the IIC bus. The manufacturer realizes that you might want to have several of these chips on the same IIC bus, which means they each need a different IIC bus address. These pins allow you to pick one of 8 pre-defined addresses ...

8

ECL outputs are referenced to the most positive supply rail. This means that any noise appearing on the most positive supply rail will be directly coupled onto the output signal. For example, if the power supply is 5V and GND, then all outputs would be referenced to 5V, and any noise on the 5V supply would also be seen at the ECL outputs. Therefore, the ...

8

You can use a third harmonic filter (inductor and capacitor) to resonate at clk*3 and then a schmitt trigger inverter (or other gate) to turn the sine wave into a decent square wave at clk*3. This works because a typical square wave has fundamental and odd harmonics in its spectrum: - The blue waveform is the output from the tuned circuit when excited by ...

8

The time required for a gate to switch is dependent upon the amount of capacitive load it must drive, the size of the transistors, and the number of transistors in series. An inverter consists of one NFET (N-channel Field Effect Transistor) and one PFET (P-channel FET); a three-input NAND gate has three PFETs in parallel and three NFETs in series. In order ...

7

A microcontroller could do it very easily. Since there are only 256 possible combinations, a simple lookup table would be the fastest way. (I did the below outputting 8 for all high for consistency, you can change the last entry to 7 if you want). The code could look something like this:- unsigned char lut[256] = {0x0, 0x1, 0x1, 0x2, 0x1, 0x2, 0x2, 0x3, ...

6

The most common way it to use a PLL based frequency multiplier. Source (www.ee.ucl.ac.uk/~pbrennan/E771/PLL.ppt‎) The Phase Locked Loop works for frequency of a signal (or more correctly -phase), like an op-amp works for Voltage. It has a high enough gain to keep the two inputs of the phase detector equal in frequency (and usually phase). Applying a ...

6

This is a simple job for a microcontroller. Spehro correctly points out that it can be accomplished with a simple lookup. If you can tolerate lower speed then counting the bits in a loop will do it too, but will take less code space. Another way is to do this in analog. Put a 100 kΩ resistor in series with each digital output, then feed that into a ...

6

If the NAND gate is made in the obvious way (three parallel transistors to GND and three series transistors to Vdd) then it will have low source capability, the transitions will not be sharp, and the delay time will be load capacitance dependent. Adding a buffer (or two to restore the logic) cleans up all those problems. Here is what a typical unbuffered ...

5

Like this:- simulate this circuit – Schematic created using CircuitLab

5

It simply relies on the phenomenon called propagation delay. Consider the following circuit. When simulated, you'd find that it doesn't stabilize in either low or high state. It simply oscillates. If you were to probe such circuit in reality with a scope, you'd find that it's output has a somewhat fixed frequency - derived from the system's propagation ...

5

From the older machines that I have looked at, often a clock was kept running via a small cell battery. And the time on that clock at start up was checked and used for various calculations. I'll try to dig up a concrete example when I get home from work! Edit: One common way of implementing this was through the classic 555 timer chip, circia 1971 (Either ...

4

This is silly if you are just trying to communicate the logic of a chip. Probably it is drawn this way because internally there are some buffering stages. The internal gates are probably very small with little drive capability. Signals that go outside need to go thru a buffer that can source and sink much more current. Somehow this implementation detail ...

4

If you want to add two N-bit numbers, a parallel adder will use N copies of a full-adder circuit, and it will produce a result in one clock cycle. On the other hand, a serial adder will use just one full-adder circuit, but it will require N clocks to produce the result. The tradeoff is circuit complexity (and power consumption) vs. time. Some examples: A ...

4

It's a subtle point, but your thinking is going astray when you think of a 330-Hz tone as somehow conveying 660 bits/second of information. It doesn't — and in fact, a pure tone conveys no information at all other than its presence or absence. In order transmit information through a channel, you need to be able to specify an arbitrary sequence of ...

4

The problem with having more than 2 variables in an axis is that terms that have a single bit difference are no longer adjacent to each other, which makes interpretation more difficult. This is why (2-dimensional) Karnaugh maps usually have no more than 2 variables per axis and no more than 4 variables per "slice".

3

The voltage that must be greater than $V_{TN}$ is the voltage from the gate to the source, $V_{GS}$, not just the voltage at the gate. Once the source voltage rises to $V_{DD} -V_{TN}$ the voltage from the gate to the source will just equal $V_{TN}$. Any increase in the source voltage will cause $V_{GS}$ to be less than $V_{TN}$ so current flow ...

3

"State machine" is a very generic term for any process (electronic or otherwise) whose output is not simply a function of its current inputs, but also depends on its past history. In other words, it has "memory", or internal state information. Electronic state machines started out as analogs of the mechanical state machines (including such examples as ...

2

Assume an initial condition S = 0, R = 0, Q = 0, Q_bar = 1. (1) SR = 00 Now consider NOR1(top), inputs of this gate is R = 0, Q_bar = 1 this gives output Q = 0. at NOR2, inputs are S = 0, Q = 0 this gives output Q_bar = 1. (2) SR = 00 to 01 change occurs at R (0 to 1) at NOR1, inputs are R = 1, Q_bar = 1 this gives output Q = 0. at NOR2, inputs are ...

2

The A0 output (aka PC0) on the Atmega328 works for everyone else, so the issue is either in your software, or in what you have connected to it. To eliminate the software aspect, start with minimal code which sets the output high and leaves it there: void setup () { DDRC = 1; PORTC = 1; } void loop () { } If the flickering occurs then the issue is ...

2

Technically, yes. This is how you get the NOR function: simulate this circuit – Schematic created using CircuitLab And if you can get NOR or NAND you can get any other gate. Though, since it takes two deMUXes to get a NOR, I don't know if it strictly is universal.

2

Since you only care about deviations from recent "average", what you want is a high pass filter. This also eliminates the large DC offset you have on your readings, and allows you to amplify the differences without amplifying this DC offset along with it. You have to decide how long "average" takes. In less hand waving terms, this means you have to decide ...

2

This is only a partial answer, but hopefully it gets at the main points you're misunderstanding. My problem is that I'm having a hard time understanding why bandwidth relates to bit rate at all. ... If a zero is expressed as a 30 Hz carrier frequency, a one is expressed as a 330 Hz carrier frequency, and the modulation signal is 330 Hz, then the ...

2

Your reference oscillator p-p voltage is a 5V logic level: - The chip is a standard 4000 series CMOS part that has voltage levels of: - You're running at 10V and the guaranteed minimum high voltage level on a 10V supply is 7.5 volts. Do you see where this might be your problem?

1

The last piece you need is a multiplexer, specifically a 1-of-4 multiplexer such as the 74153. Since you have 4 inputs to the decoder you will need 2 chips at 2 multiplexers per chip. Connect the A and B inputs to S0 and S1, each of the C inputs to each of the function output bits in turn, and the Y outputs to the decoder inputs.

1

Typically I2C devices have a base address, and then a few alternate addresses that can be selected with these pins. If the base address is 0x60 and you set up 0x02 on the pins the final address of the device would be 0x62, for example. This allows multiple identical devices to exist on the same I2C bus. With three pin you could have 8 of these memories on a ...

1

74LS32 is a LSTTL series chip (really DTL). If you leave the inputs unconnected they are effectively at "1". You need to ground each input to get a "0". Each input has a 20K typical pullup resistor.

1

The five 2:4 decoders are simply being used to construct a 4:16 decoder. Each output from this decoder represents one of the 16 possible combinations of input values. This part is going to be the same for any 4-input function. The only part you need to "design" is which of these 16 outputs you connect to the big NOR gate, and this is simply all of the ...

1

To construct the truth table, you need to manually assess each combination. A table works well, hence the name "truth table"! I assume you understand logical ANDs and ORs, to make sense of this answer. First, you want to solve each ANDed group separately. Boolean algebra has the same order of precedence as standard algebra, with AND treated like ...

1

Formally, the demultiplexer is not universal (functionally complete) because it is falsity-preserving -- that is, if you set all the inputs to 0, you can't get a 1 out of any combination of demuxes. (Note that a demux actually calculates two functions, and would therefore be considered two "gates" in abstract logic: the AND gate and a does-not-imply gate. ...

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