# Electrical Technology Grade 12 NSC June 2022 QP (Eng)

> Grade 12 Electrical Technology question paper from the NSC June Exam 2022 (English), 27 pages. Read online or download the free PDF.

- Page: https://www.hlayiso.com/library/electrical-technology-may-june-2022-digital-eng/d566fd2a-d854-43c7-887f-043f219d6078
- Updated: 2026-09-27
- Subject: Electrical Technology
- Grade: Grade 12
- Document type: Question paper
- Year: 2022
- Exam period: NSC June Exam
- Curriculum: CAPS
- Pages: 27

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Electrical Technology · Grade 12 · NSC June Exam · 2022. Question paper, 27 pages. Read online or download the PDF.

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             SENIOR CERTIFICATE EXAMINATIONS/
         NATIONAL SENIOR CERTIFICATE EXAMINATIONS

             ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS

                                         2022

                                                                       MARKS: 200

                                                                      TIME: 3 hours

           This question paper consists of 17 pages, a 1-page formula sheet
                                and 9 answer sheets.

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INSTRUCTIONS AND INFORMATION

1.       This question paper consists of SIX questions.

2.       Answer ALL the questions.

3.       Answer the following questions on the attached ANSWER SHEETS:

         QUESTIONS 3.3.5, 3.4.6, 3.6.1 and 3.6.2
         QUESTION 4.2.3
         QUESTIONS 5.3.1, 5.4.1, 5.4.2, 5.5, 5.6.1 and 5.8
         QUESTION 6.11

4.       Write your centre number and examination number on every ANSWER SHEET
         and hand them in with your ANSWER BOOK, whether you have used them or
         not.

5.       Sketches and diagrams must be large, neat and FULLY LABELLED.

6.       Show ALL calculations and round off answers correctly to TWO decimal
         places.

7.       Number the answers correctly according to the numbering system used in this
         question paper.

8.       You may use a non-programmable calculator.

9.       Calculations must include:

         9.1         Formulae and manipulations where needed

         9.2         Correct replacement of values

         9.3         Correct answer and relevant units where applicable

10.      A formula sheet is attached at the end of this question paper.

11.      Write neatly and legibly.

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QUESTION 1: MULTIPLE-CHOICE QUESTIONS

Various options are provided as possible answers to the following questions. Choose
the answer and write only the letter (AD) next to the question numbers
(1.1.1 to 1.1.15) in the ANSWER BOOK, e.g. 1.16 D.

1.1        The layer(s) of the skin that is/are affected by a third-degree burn would be …

           A     the outer layer.
           B     the second layer.
           C     all layers of the skin.
           D     None of the above-mentioned.                                                        (1)

1.2        A/An … circuit is used to clean up an input signal which has been distorted.

           A     integrator
           B     differentiator
           C     Schmitt trigger
           D     comparator                                                                          (1)

1.3        Open-loop gain with reference to op amps is when …

           A     a feedback resistor is connected from the output to the inverting input.
           B     no feedback resistor is connected from the output to the input.
           C     a capacitor is connected from the output to the inverting input.
           D     a feedback resistor is connected from the output to the non-inverting
                 input.
                                                                                                     (1)

1.4        When a triangular waveform is applied to the input of a differentiator, the
           output waveform will be a/an …

           A     DC level.
           B     inverted triangular waveform.
           C     first harmonic frequency of the triangular waveform.
           D     square waveform.                                                                    (1)

1.5        The basic circuit of a passive RC differentiator is a …

           A     capacitor in series with the input and a resistor in parallel with the
                 output.
           B     resistor in series with the input and a capacitor in parallel with the
                 output.
           C     resistor in series with the input and a resistor in parallel with the output.
           D     capacitor in series with the input and a capacitor in parallel with the
                 output.                                                                             (1)

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1.6        Phase shift through an op amp is caused by the …

           A     cut-off frequency.
           B     internal RC circuits.
           C     notch frequency.
           D     unity-gain frequency.                                                           (1)

1.7        Negative feedback in an op amp …

           A     increases the input and output impedances.
           B     decreases the output impedance and the bandwidth.
           C     increases the input impedance and the bandwidth.
           D     does not affect impedances or the bandwidth.                                    (1)

1.8        A … output is the transistor collector connected to the cathode of the LED.

           A     sourcing
           B     draining
           C     distributing
           D     sinking                                                                          (1)

1.9        The … is designed to accept input data in decimal form and convert this
           information into its binary form.

           A     decoder
           B     seven-segment display
           C     encoder
           D     half-adder                                                                       (1)

1.10       A combinational logic circuit combining an AND gate with an exclusive
           OR gate (XOR) is called the … circuit.

           A     half-adder
           B     full adder
           C     parallel adder
           D     arithmetic                                                                      (1)

1.11       The … is where the timing signal is delayed by a fraction of time through
           each flip-flop.

           A     ripple counter
           B     down counter
           C     frequency divider
           D     propagation delay                                                               (1)

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1.12       A fast temporary memory that allows information to be stored and retrieved
           by the system as it operates, is called the …

           A     ROM.
           B     RAM.
           C     CPU.
           D     I/O unit.                                                                        (1)

1.13       A register that contains the address and status of the next instruction for
           processing and also tells the processor what the next instruction is, is called
           the …

           A     program counter.
           B     memory address register.
           C     accumulator.
           D     current instruction register.                                                    (1)

1.14       The bus that is used to transmit the memory address from the memory and
           input/output ports to the CPU is called the … bus.

           A     system
           B     control
           C     data
           D     address                                                                          (1)

1.15       ONE advantage of the serial peripheral interface bus (SPI) is that it …

           A     cannot transmit off the PCB.
           B     is susceptible to noise.
           C     supports high-speed full-duplex communication.
           D     supports only one master device on the bus.                                      (1)
                                                                                                  [15]

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QUESTION 2: OCCUPATIONAL HEALTH AND SAFETY

2.1        Explain the term machinery with reference to the Occupational Health and
           Safety Act, 1993 (Act 85 of 1993).                                                  (2)

2.2        Explain the term critical incident with regard to emergencies.                      (2)

2.3        State TWO steps you should take when you discover a fire in an electrical
           workshop.                                                                           (2)

2.4        State the importance of wearing a face mask in the workshop.                        (2)

2.5        Name TWO environmental considerations when working with chemicals
           during the printed circuit board manufacturing process.                             (2)
                                                                                               [10]

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QUESTION 3: SWITCHING CIRCUITS

3.1        Name the type of multivibrator that:

           3.1.1        Produces one pulse cycle of 'high' and 'low' when a trigger pulse is
                        applied to its input                                                           (1)

           3.1.2        Changes state when a trigger pulse is applied and remains in that
                        state                                                                          (1)

3.2        Refer to FIGURE 3.2 below and answer the questions that follow.

                                               +9V

                         R2            R1
                        10 kΩ         10 kΩ
                                                                           R3
                                                     4       8           470 Ω
                                                     7   555         3
                                                     6
                                                     2
                                                         1       5
                                                                                 LED

                           Set         Reset
                                                                      C1
                                                                     10 nF

                                 FIGURE 3.2: BI-STABLE MULTIVIBRATOR

           3.2.1        Name the function of resistors:

                        (a)    R1                                                                      (1)

                        (b)    R3                                                                      (1)

           3.2.2        Identify the state of the LED when trigger pin 2 is high.                      (1)

           3.2.3        Explain what happens in the circuit when the set switch is pressed.            (2)

           3.2.4        Explain the purpose of connecting pin 6 to ground.                             (2)

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3.3        FIGURE 3.3 below shows an op amp as a comparator. The resistance of the
           LDR increases as the level of light falls.

                                                                 +V

                              R1
            V        Vin   100 kΩ
                                                                          R3
                           Vref                                          1 kΩ
                                                               741
                            t
                                               R2
                                             100 kΩ                                       LED 2
                                LDR                                       LED 1           white
                                                                           red

                                                                                          0V
                                                  -V
                     FIGURE 3.3: OP AMP COMPARATOR AS A DARK SENSOR

           3.3.1           State the purpose of R2.                                                     (1)

           3.3.2           Explain how an increase in the level of light affects the voltage on
                           the non-inverting input.                                                     (2)

           3.3.3           Explain the operation of the circuit with reference to the voltages on
                           the input terminals and the output voltage.                                  (3)

           3.3.4           Predict the state of LED1 and LED2 when the voltage on the
                           inverting terminal is higher than the voltage on the non-inverting
                           terminal.                                                                    (2)

           3.3.5           Draw the output on the ANSWER SHEET for QUESTION 3.3.5.                      (3)

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3.4        Refer to FIGURE 3.4 below and answer the questions that follow.

                                       VIN                      +10 V
                     V
                      0
                                   t                                               VOUT

                                                                             RF
                                                                -10 V       9 kΩ
                            1V
                              0
                                                  t                          R1
                            -1 V
                                                                            1 kΩ
                                                                                   0V

                                             FIGURE 3.4: SCHMITT TRIGGER

           3.4.1          Identify the type of Schmitt trigger circuit.                               (1)

           3.4.2          Determine the value of the output voltage when the voltage on the
                          non-inverting input is -1 V.                                                (1)

           3.4.3          State whether this circuit uses positive or negative feedback.              (1)

           3.4.4          Explain the operation of the circuit with reference to the input and
                          trigger voltage levels.                                                     (4)

           3.4.5          Predict how an increase in the value of R1 will affect the trigger
                          voltage level.                                                              (1)

           3.4.6          Draw the output             signal   on   the   ANSWER   SHEET      for
                          QUESTION 3.4.6.                                                             (4)

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3.5        Refer to FIGURE 3.5 below and answer the questions that follow.

                                                                 RF 100 kΩ
                                        C1   R1 10 kΩ
               0,4 V

                                        C2   R2 10 kΩ                  +9 V
               0,5 V                                              -

                                        C3   R3 10 kΩ             +
              0,25 V                                                                       VOUT
                                                                       -9 V
                                                                 0V

                                    FIGURE 3.5: SUMMING AMPLIFIER

           3.5.1           The variable resistor RF serves a dual purpose. Name both
                           purposes.                                                                (2)

           3.5.2           Calculate the output voltage when the value of RF is set to
                           78,26 kΩ.                                                                (3)

           3.5.3           Explain how an increase in the value of RF affects the gain of the
                           amplifier.                                                               (1)

           3.5.4           Describe why it is not recommended to increase the value of RF
                           beyond 78,26 kΩ.                                                         (4)

           3.5.5           Explain how this limitation can be overcome without changing the
                           value of any of the resistors.                                           (2)
3.6        Refer to FIGURE 3.6 below and answer the questions that follow.

                       V                                         R
                                                                1 kΩ
                   Input
                                                      VIN                           VOUT
                                                  t
                                                 Vsupply                        C
               Output                                                         10 µF

                                                 t

                                 FIGURE 3.6: PASSIVE RC INTEGRATOR
           3.6.1           Draw the output when the value of C is changed to 1 µF on the
                           ANSWER SHEET for QUESTION 3.6.1.                                         (3)
           3.6.2           Draw the output when the value of C is changed to 100 µF on the
                           ANSWER SHEET for QUESTION 3.6.2.                                         (3)
                                                                                                    [50]

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QUESTION 4: SEMICONDUCTOR DEVICES

4.1        FIGURE 4.1 below shows the 555 IC. Answer the questions that follow.

                                    0V       1               8   +Vcc

                              TRIGGER        2               7    DISCHARGE
                                                  555 IC
                               OUTPUT        3               6    THRESHOLD
                                                                 CONTROL
                                RESET        4               5
                                                                 VOLTAGE

                                      FIGURE 4.1: 555 IC PIN LAYOUT

           4.1.1        Briefly describe the functions of pin 6 with reference to the 555 IC.         (3)

           4.1.2        State the supply voltage range at which the 555 IC operates.                  (2)

           4.1.3        Explain the function of the SR flip-flop in the internal circuit of the
                        555 timer.                                                                    (2)

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4.2        Refer to FIGURE 4.2 below and answer the questions that follow.

                                                                       Vcc = +5 V to 15 V

                             R1              R2                8            4
                                                                                            Vout
                                                           7                    3
                                                                   555 IC
                                                           6
                1
                                                           2
                0                                                  5            1
                   Trigger
                    Input                C1
                                                   C = 0,01 µF
                     (S1)

                                                                                            0V

                                  FIGURE 4.2: 555 IC MULTIVIBRATOR

           4.2.1       Identify the multivibrator in FIGURE 4.2.                                          (1)

           4.2.2       Give a brief description of what happens when the push-to-make
                       switch (S1) is activated.                                                          (4)

           4.2.3       Draw on the ANSWER SHEET for QUESTION 4.2.3 the voltage
                       waveform of the capacitor C1 and the output voltage waveform when
                       the trigger input is pressed.                                                      (4)

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4.3        Refer to the astable multivibrator in FIGURE 4.3 below which has an output
           frequency of 1 hertz. Answer the questions that follow.

                                                                                   9V

               R1

                                             4       8
                                       7
                                                              3
                                                                                 Vout
                                                 555                          f = 1 Hz
                R2                                                     R3

                                       6

                                       2 1                5            LED

              C1                                                  C2

                                                                                   0V

                                FIGURE 4.3: ASTABLE MULTIVIBRATOR

           4.3.1        Explain the mode (state) of the LED.                                    (2)

           4.3.2        Explain the effect on the LED when:

                        (a)    R2 is halved                                                     (1)

                        (b)    The value of C1 is doubled                                       (1)
                                                                                                [20]

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QUESTION 5: DIGITAL AND SEQUENTIAL DEVICES

5.1        Answer the following questions with reference to the seven-segment
           LED display.

           5.1.1        Describe the difference between common-anode and common-
                        cathode connections.                                                          (2)

           5.1.2        Draw the circuit of a sourcing digital output using an LED and a
                        transistor. Indicate the direction of current flow at the output.             (5)

5.2        Refer to FIGURE 5.2 below and answer the questions that follow.

                                               Grid A                 Grid B

                                                                         Rotated
                                                                           90º
                             Radiating
                               light

                                     FIGURE 5.2: POLARISING GRIDS

           5.2.1        Explain the process when light waves pass through grid A.                     (2)

           5.2.2        State the effect that grid B has on the light waves.                          (1)

5.3        Answer the following questions with reference to encoders and decoders.

           5.3.1        Complete the circuit diagram of a three-digit decimal input to
                        two-bit binary output encoder on the ANSWER SHEET for
                        QUESTION 5.3.1.                                                               (6)

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          5.3.2         FIGURE 5.3.2 below shows a circuit diagram of a two-digit binary
                        input to four-digit decimal output decoder. Determine the output at
                        W, X, Y and Z when input A is '02' and input B is '12'.

                                    A=0

                                    B=1
                                                                                W

                                                                                X

                                                                                Y

                                                                                Z

                                                     FIGURE 5.3.2                                      (4)

5.4       FIGURE 5.4 below represents the logic symbol of a D-type flip-flop.

                                             D                        Q

                                        CLK

                                                                      Q

                                                 FIGURE 5.4

          5.4.1         Complete the logic circuit of this flip-flop using the information
                        given on the ANSWER SHEET for QUESTION 5.4.1.                                  (6)

          5.4.2         Complete the truth table of this flip-flop in the table below on the
                        ANSWER SHEET for QUESTION 5.4.2.

                                     INPUTS                       OUTPUTS
                                  CLK       D                 Q             Q
                                    0            0                 Latch
                                    0            1
                                    1            0
                                    1            1
                                                 TABLE 5.4.2                                           (3)

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5.5       FIGURE 5.5 below represents the logic symbol of a full adder. Complete the
          logic circuit of the full adder using the information given on ANSWER
          SHEET 5.5.

                                      A
                                                                             Σ

                                      B
                                                    F/A
                                                                             CO
                                      Ci

                                                    FIGURE 5.5                                             (8)

5.6       Refer to FIGURE 5.6 below of a three-stage binary counter and answer the
          questions that follow.

                                  1                    A                 B                        C

                                          FF0                  FF1                    FF2
                                          SET                  SET                    SET
                                      J         Q          J         Q            J         Q

                                      K   CLR   Q          K   CLR   Q            K   CLR   Q

                    Input
                clock pulses

                               FIGURE 5.6 THREE-STAGE BINARY COUNTER

          5.6.1          Complete the timing diagrams for this counter on the ANSWER
                         SHEET for QUESTION 5.6.1.                                                         (8)

          5.6.2          State whether the circuit in FIGURE 5.6 is synchronous or
                         asynchronous.                                                                     (1)

5.7       State TWO applications of the up/down counter.                                                   (2)

5.8       Complete the sketch of a 4-bit serial-in: serial-out shift register using the
          information given on the ANSWER SHEET for QUESTION 5.8.                                          (7)
                                                                                                           [55]

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QUESTION 6: MICROCONTROLLERS

6.1        Name TWO uses of a microcontroller in industrial control devices.                      (2)

6.2        Draw the sequential operating (scan) cycle of the CPU.                                 (4)

6.3        Explain the difference between a microprocessor and a microcontroller with
           reference to the hardware of microcontrollers.                                         (4)

6.4        Refer to registers within the CPU and answer the questions that follow.

           6.4.1      Explain the function of a memory data register (MDR).                       (2)

           6.4.2      Explain the function of a current instruction register (CIR).               (3)

6.5        Refer to communication in a microcontroller and define the term hardware
           interface.                                                                             (2)

6.6        Draw a block diagram of full duplex communication.                                     (4)

6.7        Answer the following questions with reference to serial communication
           interface.

           6.7.1     Write out the abbreviation UART in full.                                     (1)

           6.7.2     List THREE advantages of the UART.                                           (3)

           6.7.3     Explain the operation of the UART.                                           (6)

6.8        Answer the questions that follow with reference to communication protocols.

           6.8.1     Name THREE applications of the RS-485.                                       (3)

           6.8.2     State the line configuration of the RS-485.                                  (1)

6.9        State the purpose of an analogue-to-digital-converter (ADC) with reference to
           the hardware of microcontrollers.                                                      (3)

6.10       Explain the relationship between algorithms and flowcharts with reference to
           the software of microcontrollers.                                                      (4)

6.11       Complete the flow chart of a monitoring system at a fuel station on the
           ANSWER SHEET for QUESTION 6.11.

           A fuel station has three tanks, each with a level-monitoring sensor. The
           sensors will be activated when the fuel level reaches the bottom of each tank.
           The alarm will sound if any of the sensors is activated. The system must
           include a reset function. NO time delay is needed.                                     (8)
                                                                                                  [50]

                                                                                      TOTAL:      200
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                                               FORMULA SHEET

SEMICONDUCTOR DEVICES
             VOUT       RF                           RF
Gain A V                    OR        AV  1
              VIN       R IN                         RIN
               R 
VOUT  VIN    F 
               R IN 
                 R 
VOUT  VIN  1  F 
                 R IN 
SWITCHING CIRCUITS
           R        R         R 
VOUT    V1 F  V2 F  ...VN F 
           R1       R2        RN 
              VOUT         VOUT
Gain A V          
               VIN   V1  V2  ...VN 
VOUT   (V1  V2  ...VN )

FLOW CHART SYMBOLS

                              Process

                              Decision

                              Terminator

                                Data

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CENTRE NUMBER:

EXAMINATION NUMBER:

ANSWER SHEET

QUESTION 3: SWITCHING CIRCUITS

3.3.5                          Vin
                   V

                                             Vref
            Input

                                             t

                                         Vsat
                                                                         Transfer mark to
                                                                         answer book
          Output

                                                                                       MOD
                                      t
                               FIGURE 3.3.5                                                   (3)

3.4.6        +V

                                                    Upper trigger
                                                      voltage

               0

                                                    Lower trigger
                                                      voltage

              -V

           +Vsat

               0                                                    Transfer mark to
                                                                    answer book

                                                                                MOD
           -Vsat

                               FIGURE 3.4.6                                                   (4)

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CENTRE NUMBER:

EXAMINATION NUMBER:

ANSWER SHEET

3.6.1             V

            Input

                                                         t

                                                     Vsupply
                                                                      Transfer mark to
                                                                      answer book
          Output

                                                 t                                MOD

                               FIGURE 3.6.1                                                    (3)

3.6.2            V

            Input

                                                     t

                                                 Vsupply
                                                                      Transfer mark to
                                                                      answer book
         Output

                                             t                                    MOD

                               FIGURE 3.6.2                                                    (3)

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CENTRE NUMBER:

EXAMINATION NUMBER:

ANSWER SHEET

QUESTION 4: SEMICONDUCTORS

4.2.3
                       V
                                              Trigger       t
                                              input

            Capacitor
             voltage

                                                                t
                                                                    Transfer mark to
                                                                    answer book
             Output
             voltage

                                                                                MOD

                                                                t                            (4)
                                             FIGURE 4.2.3

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CENTRE NUMBER:

EXAMINATION NUMBER:

ANSWER SHEET

QUESTION 5: DIGITAL AND SEQUENTIAL DEVICES

5.3.1
                                                                          +5 V

                                      R1     R2     R3

                               S1
                1
                                                                            A0
                               S2
                2

                               S3
                3                                                           A1

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                                                                             MOD

                                                  FIGURE 5.3.1                           (6)

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### Page 23

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5.4.1

                   D
                                                                  Q

                CLK

                                                                  Q

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                                                                        MOD

                                             FIGURE 5.4.1                           (6)

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                                             SC/NSC

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5.4.2
                     INPUTS                      OUTPUTS
                  CLK       D                Q             Q
                     0             0              Latch        Transfer mark to
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                     0             1
                     1             0
                     1             1
                                                                           MOD

                                             TABLE 5.4.2                                (3)

 5.5

            Ci
                                                                              Σ

            A
                                                                            Co
            B

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                                             FIGURE 5.5                                 (8)

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5.6.1
                             1        2      3       4     5    6   7     8
           Clock pulses

              Output A

              Output B

              Output C

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                                                 FIGURE 5.6.1                                   (8)

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 5.8
             Serial
                       D       Q
            Data in
                             FFA
           Clock       CLK     Q
                                             D     Q
                                                 FFB

                                         CLK       Q

                                                                D           Q
                                                                      FFC
                                                                CLK     Q
                                                                                                   Serial
                                                                                D        Q        Data out
                                                                                      FFD
                                                                                CLK      Q

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                                                       FIGURE 5.8                                             (7)

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QUESTION 6: MICROCONTROLLERS

6.11

                          Start

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                                                                       MOD

                                             FIGUUR 6.11                           (8)

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