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electrical engineering save > deck_5717481 > Flashcards

deck_5717481 Flashcards

1
Q

What are the advantages of digital electronics over analogue ?

A

Low mass production costsImplementation of complex algorithmsNo drift or ageing problems (As it heats up and cools down over time)Good immunity to noise and signal degradation

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2
Q

What happens to noise when a digital and analogue signal is processed?

A

In digital the noise to totally removed.Analogue the noise gets worse

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3
Q

What is combinational logic?

A

Provides and output the is dependent on the input at that point in time. Like a light switch

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4
Q

Sequential logic

A

An output is determined not only by current input but also previous history. Like a pull cord switch in a bathroom.

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5
Q

Synchronous logic

A

A clock switches between 1 and 0 to ensure all the sub-systems are synchronised.

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6
Q

What is the most significant bit?

A

The left most bit

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7
Q

If you have n bits, how many numbers can you store?

A

2^n numbers. Remember to include 0

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8
Q

What is a byte?

A

A group of 8 bits

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9
Q

What is a word?

A

A group of bits used to store a word.

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10
Q

Convert 7B to denary

A

716^1 + 1116^0=123

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11
Q

A to denary

A

10

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12
Q

B to denary

A

11

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13
Q

C to denary

A

12

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14
Q

D to denary

A

13

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15
Q

E to denary

A

14

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16
Q

F to denary

A

15

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17
Q

How do you convert denary to hexadecimal ?

A

Divide by 16. The remainder is the least significant digit. Continue until you have one remainder left which is the most significant digit. If the remainder was 13 it would be D.

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18
Q

Why isn’t binary used in measurement of real things?

A

A slight miss-alignment of the sensor would cause a miss reading.

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19
Q

What is the nature of grey code?

A

Going from number to number only one digit changes

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20
Q

How do you convert from 3 bit binary to grey code?

A

The most significant bit of the grey code is the same as for the binaryFor all other bits if it is the same as the one before it is 0. If different it is 1

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21
Q

What is an ADC?

A

Analogue to digital converter. Takes a continuously varying input and converts to binary numbers.

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22
Q

What is quantisation error?

A

The difference between the digital and analogue signal.

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23
Q

How can the quantisation error be reduced?

A

Increase the number of bits.

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24
Q

How do you find the quantisation error?

A

voltage step = (Vmax-Vmin)/2The error is half of this again.

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25
Q

How does an and gate work?

A

If both inputs are 1, output is 1Otherwise output is 0.Referred to as the logical product.

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26
Q

What is the symbol of an and gate?

A

A square with the side where the output comes from is rounded off.

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27
Q

How does an or gate work?

A

If both the inputs are 0, the output is 0Otherwise the output is 1.Sometimes referred to as the logical sum of A and B

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28
Q

What is the symbol for the or gate?

A

A shield on its side with the output coming from the pointy end.

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29
Q

What are the different types of or?

A

Inclusive or which is used by the or gateExclusive or which only returns 1 when the two inputs are different.C=A⊕B

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30
Q

What is the symbol for an inverter?

A

A triangle pointing to the right with a circle at the pointB=À

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31
Q

What should A+B.C be interpreted as?

A

A+(B.C)And has precedence over or.

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32
Q

How would you estimate the complexity of an equation?

A

Add together the total number of inversions. (little hats)The number of plus signs and the total number of letters.

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33
Q

What are the rules governing the size of a group in a karnough map?

A

must be 1,2,4,8…

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34
Q

What is de morgan’s law?

A

(A.B)=(A)+(B)(A+B)=(A).(B) where () denote an invertion

35
Q

What is a Nand gate?

A

And and gate with an inverter at the endc=(A.B)

36
Q

What is the truth table for the RS latch?

A
37
Q

What is the truth table to the active low RS latch?

A
38
Q

What is the truth table for the JK flip-flop

A
39
Q

What is the truth table for the T flip flop?

A
40
Q

what is the truth table for the D flip flop?

A
41
Q

What is a multiplexer?

A

It has many data inputs and one data output. The user can select one of the data inpus to be steered through to the ouput.

42
Q

What are the s inputs of a multiplexar for?

A

To select the input with use of a binary number. You would need three if you had 8 inputs.

43
Q

What is a de-multiplexer?

A

A device that takes a single input and steers the contents through to one of many data outputs dependong on the s values.

44
Q

How do you design a counter?

A

Draw these tables. Then drae K maps with Q values now on the axis for each of the T columns.Then attach several T flip flops together, all connected directley to the clock and wire up accordingly.

45
Q

What is a modulo counter?

A

Used when the number of inputs is not equal to 2^n.For examle a modulo 6 counter would go through the sequency 0,1,2,3,4,5,0,1,2,3…

46
Q

How would you design a modulo 6 counter?

A

3 Q values are needed as 2^3 is 8 which is the smallest number that will accomidate 6.If it goes into a state like 6 or 7 it should go to 0 to avoid accidents.Procede as normal.

47
Q

How does an up/down counter function?

A

An input controls the direction of count. If down=1 it is a down counter 0,3,2,1,0….If down =0 it does, 0,1,2,3,0…

48
Q

How do you design an up/down counter?

A

Draw a table of all possible combinations of down and the Qs. Draw anouther of the next stage needed and the T table. Draw K maps and wire up with T flip-flops

49
Q

What is the standard symbol for the 2 bit multiplexar?

A
50
Q

What is a shift register?

A

A series of D flip-flops, with the Q output of one leading into the D input of the next.

51
Q

What is a PISO shift register?

A

Parallel input serial output.

52
Q

What is a SIPO?

A
53
Q

How do you tell if adder overflow has occoured in unsigned binary?

A

Look at the final carry output. If this is a 1 it has over flowed. This is a status flag.

54
Q

What is a carry ripple adder?

A

A series of full adder put together. However, each adder adds a bit of a time delay.

55
Q

How can the build of delays in an adder be mitigated?

A

All of the carry on values can be expressed in terms of all the previous A and B values. This means they can be calculated from the starts without waiting for anything else.

56
Q

How does the XNOR gate work?

A
57
Q

How would you make a equality detector?

A

The XNOR gate outputs a 1 when the two inputs are the same. Put all the pairs of bits through a different XNOR gate and and the results together. When equal it should give a 1.

58
Q

What is the 2s complement number system?

A

The most significant bit is negative

59
Q

How do you convert a number to the negative?

A

Write is positive.Invert each 1 to 0 and 0 to 1Add 1

60
Q

How would you add bits to a negative 2s compliment number?

A

If it was positive you would just add 0s to the front.When negative add 1s to the front

61
Q

What modifications need to be done to an adder so it can add signed binary?

A

None, it will work fine.

62
Q

How are numbers subtracted?

A

Convert one of the numbers to a negative and add together. This can be done with an ordinary adder by putting inverters on all the B or A inputs and making Cin=1

63
Q

How can a circuit that adds and subtracts be produced?

A
64
Q

What is an ALU?

A

Arithmetic logic unit. You specify numbers which you want to add and the operation you want to get a given output.

65
Q

How can you tell if there is overflow in signed binary?

A

When the most significant bit’s Cinand Coutare different.(That is the remainder that it produces and the remainder it gotfrom the bit to the right)

66
Q

What are the four basic parts of programmable sum-of-products function?

A

An input stage, an AND plane, giving products, an OR plane evaluating sums and an output stage that might include filp flops.

67
Q

What does PLD stand for?

A

Programmiable logic device

68
Q

How is a programmable logic device programmed?

A

High power current is sent through certain wires to melt certain fuses to give certain functions

69
Q

What a way of notation that is useful when drawing large PLDs?

A

An X deonotes a connection. Thus C isn’t connected to the OR gate.

70
Q

What does PROM mean?

A

Programmable read only memory. Where the AND array is fixed and the OR array is programable

71
Q

What does PAL mean?

A

Programmable array logic where the AND array is programmable but the OR array is fixed.(Also known as generic array logic and programmable electrically erasable logic)

72
Q

What is a PLA?

A

Programmable logic array. Where both the AND and OR array are programmable.

73
Q

What is RAM?

A

Random Access Memory. New data items can be stored into the memory, old data iteams can be read out

74
Q

What is ROM?

A

The data contained is fixed at the time of programming and can’t be changed untill reprogramming. We can read data butcan’t write more.

75
Q

What is volatile memory?

A

When the power is turned off the memory is lost. RAM is this as it is voltage in a latch circuit.ROM is an absence of a connection between the AND and OR plane which will remain.

76
Q

What is a tri-state output?

A

A device that can electronically disconnect itself from its output terminal. When OE=0 it will go to a high impedance state and act as if it weren’t connected.

77
Q

What is the advantage of using a tri-state output?

A

It allows for several devices to put their outputs through the same wire without interfering.

78
Q

If on a diagram, you see a wire with a slash across it with a number, what does that mean?

A

The wire is infact 8 wires carrying 1-bit signals that form a data byte.

79
Q

What is the symbol of an ALU?

A
80
Q

What is a register?

A

A circuit with shoer term memory. A calculator would have it so that when doing 3+5 you didn’t have to press all three buttons at the same time.

81
Q

How could a register be made from D flipflops?

A

The output of a D flipflop will only change on a clock edge, meaning it has some memory. If 8 are connected to the same clock signal, they can store a byte.

82
Q

What are the main features of a microprocessor?

A

Normally designed to beone chip within a larger computer system with other chips thatmightdo RAM. Normally used in what is pecerved to be a computer. The program can be changed frequently.

83
Q

What are the main features of a microcontroller?

A

Work in an embedded system. They will only run a single program which is stored in ROM. They aim to put all the required resorces on a single chip and have very low power and resource requirments.

84
Q

What is A+1 equal to?

A

1

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