4.1 Name TWO methods to connect the LEDs of an LED seven-segment display to the supply - NSC Electrical Technology Digital - Question 4 - 2020 - Paper 1
Question 4
4.1 Name TWO methods to connect the LEDs of an LED seven-segment display to the supply.
4.2 Identify the circuit in FIGURE 4.2 below with reference to digital outpu... show full transcript
Worked Solution & Example Answer:4.1 Name TWO methods to connect the LEDs of an LED seven-segment display to the supply - NSC Electrical Technology Digital - Question 4 - 2020 - Paper 1
Step 1
Name TWO methods to connect the LEDs of an LED seven-segment display to the supply.
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Answer
Common Anode: Connect the anodes of the LEDs to a positive supply and control the cathodes to turn on the LEDs.
Common Cathode: Connect the cathodes of the LEDs to ground and apply voltage to the anodes to turn on the LEDs.
Step 2
Identify the circuit in FIGURE 4.2 below with reference to digital outputs.
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Answer
The circuit in FIGURE 4.2 is a current sourcing configuration used to control the LED, engaging it based on the input signal. The output in this case is a digital signal that can denote 'ON' or 'OFF' states for the LED load.
Step 3
With reference to the triggering of flip-flops, name the TWO classes of synchronous flip-flops.
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Pulse Triggered Flip-Flops: These are activated by a pulse at their clock input.
Edge Triggered Flip-Flops: They are activated on a specific edge of the clock signal, either positive or negative.
Step 4
Complete and label the diagram of this adder on the ANSWER SHEET for QUESTION 4.4.
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Answer
The 4-bit parallel adder consists of multiple full adders (F/A) and a half adder (H/A) connected in a structure that adds B and A inputs, with the carry inputs and outputs properly indicated.
Step 5
Complete the truth table of this decoder on the ANSWER SHEET for QUESTION 4.5.
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Inputs
Outputs
A
B
-----
-----
0
0
0
1
1
0
1
1
Step 6
State the function of a decoder.
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A decoder converts a binary code into a recognizable decimal form, allowing for digit or character representation.
Step 7
Name TWO group classifications of logic circuits with reference to memory elements.
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Answer
Combinational Logic Circuits: These circuits output based solely on current inputs without storing past states.
Sequential Logic Circuits: These circuits depend on past inputs as well as current inputs, thus featuring memory elements.
Step 8
Complete the truth table of the RS latch on the ANSWER SHEET for QUESTION 4.8.1.
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Mode of Operation
Inputs
Outputs
HOLD
0 0
Q and Q' unchanged
RESET
1 0
0 1
SET
0 1
1 0
ILLEGAL
1 1
INVALID
Step 9
Complete the output waveforms of this RS latch on the ANSWER SHEET for QUESTION 4.8.2.
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Answer
The waveforms for the RS latch will need to illustrate the changes in Q and Q' based on the input S and R as per the completed truth table.
Step 10
Explain the term propagation delay with reference to asynchronous ripple counters.
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Answer
Propagation delay is the time taken for a change in input to affect the output in a flip-flop or counter. In asynchronous ripple counters, this delay can accumulate and affect the overall speed of the circuit.
Step 11
Explain the term counter.
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A counter is a circuit that counts through a set sequence of states (numbers) when activated by a clock pulse and subsequently returns to its initial state.
Step 12
Complete the output waveforms of this counter on the ANSWER SHEET for QUESTION 4.11.1.
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The output waveforms need to show the state transitions of Output A, B, and C corresponding to the clock pulse inputs, with displays of the count values.
Step 13
Explain the purpose of the AND gate in FIGURE 4.11.
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The AND gate ensures that flip-flop FF2 produces a correct reading only when both inputs Q0 and Q1 from FF0 and FF1 are conditions met, allowing for the proper counting mechanism.
Step 14
Identify the register in FIGURE 4.12.
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A = 4-bit parallel data input.
B = 4-bit parallel data output.
Step 15
Label A and B.
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A is the data input register, and B is the data output register.
Step 16
Describe the operation of this register.
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Data is input in parallel to register A and can be transferred to register B, following a clock pulse that loads the data from A into B.
