4.1 State the light-altering principle of operation of the liquid crystal display (LCD) - NSC Electrical Technology Digital - Question 4 - 2019 - Paper 1
Question 4
4.1 State the light-altering principle of operation of the liquid crystal display (LCD).
4.2 With reference to encoders and decoders, answer the questions that foll... show full transcript
Worked Solution & Example Answer:4.1 State the light-altering principle of operation of the liquid crystal display (LCD) - NSC Electrical Technology Digital - Question 4 - 2019 - Paper 1
Step 1
State the light-altering principle of operation of the liquid crystal display (LCD).
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Answer
The light-altering principle of operation of an LCD involves the manipulation of light through liquid crystals, which can alter their alignment when an electric field is applied. This process allows for the modulation of light transmission, enabling the display of images and texts.
Step 2
Draw the circuit diagram of a simple two-digit-binary-input-to-four-digit-decimal-output decoder using TWO NOT gates and FOUR AND gates.
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Answer
The circuit diagram will consist of:
Two NOT gates for inverting inputs A and B.
Four AND gates designed to produce outputs based on the binary input combinations.
The combination of gates will ensure each output corresponds to decimal representations from 0 to 3.
Step 3
Complete the truth table of the two-digit-binary-input-to-four-digit-decimal-output decoder on the ANSWER SHEET FOR QUESTION 4.2.2.
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Answer
The truth table will have binary inputs A and B ranging from 00 to 11, producing outputs for the decimal values:
For (0, 0), output is 00
For (0, 1), output is 01
For (1, 0), output is 10
For (1, 1), output is 11
Step 4
Label input W.
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Answer
Input W should be labeled as the enable or control signal that determines whether the BCD to seven-segment decoder operates.
Step 5
Explain the function of the driver transistors found in the BCD-to-seven-segment display decoder.
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Answer
Driver transistors ensure each LED segment receives sufficient current. They allow for the individual illumination of segments in the display, providing clarity and brightness regardless of the input number.
Step 6
Complete the truth table of a BCD-to-seven-segment decoder connected to a seven-segment display in TABLE 4.3.3 on the ANSWER SHEET FOR QUESTION 4.3.3.
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Answer
The truth table will show inputs B, C, and D related to the outputs a, b, c, d, e, f, g for displaying digits 0 to 9.
Step 7
Draw the logic circuit of this half adder using an AND gate and an OR gate only.
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Answer
The logic circuit will consist of:
An AND gate to calculate the carry output.
An OR gate to calculate the sum output. The inputs A and B are connected appropriately to these gates.
Step 8
Complete the truth table of this half adder.
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The truth table will outline combinations of inputs A and B, displaying the resulting sum and carry outputs:
For (0, 0), Sum = 0, Carry = 0
For (0, 1), Sum = 1, Carry = 0
For (1, 0), Sum = 1, Carry = 0
For (1, 1), Sum = 0, Carry = 1
Step 9
Draw the logic circuit of this flip flop on the ANSWER SHEET FOR QUESTION 4.5, using NAND gates only.
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The circuit will feature:
A clock input that triggers state changes based on the NAND gates.
Proper connections to prevent both SET and RESET from being active simultaneously.
Step 10
Complete the truth table of this flip flop.
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The truth table will specify the inputs for CLK, S, R and the outputs Q and Q' at different values of these states, displaying how the flip flop reacts.
Step 11
Name TWO applications of counters.
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Answer
Frequency division in oscillators.
Decimal counting in digital clocks.
Step 12
Describe how data is introduced to the register.
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Answer
Data is typically introduced in parallel form, allowing multiple bits to be loaded simultaneously under the control of a clock signal.
Step 13
Identify the shift register in FIGURE 4.8.
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Answer
The shift register depicted is the one that allows data to shift left or right depending on control signals.
Step 14
Label A and B.
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Label A should represent the data input while Label B represents a clock control signal.
Step 15
Describe how data is shifted out of the register.
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Data is shifted out serially when the clock signal triggers the movement of bits from the register to an output pin.
Step 16
State THREE uses of this register.
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