Exam (elaborations)
1.3.5-Memory-storage-devices-and-media
1.3.5-Memory-storage-devices-and-media
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QUESTION 1. 128 An alarm clock is controlled by a microprocessor. It uses the 24 hour clock. The hour is represented
by an 8-bit register, A, and the number of minutes is represented by another 8-bit register, B.
(a) Identify what time is represented by the following two 8-bit registers.
A B
128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1
0 0 0 1 0 0 1 0 : 0 0 1 1 0 1 0 1
Hours ............................................ Minutes .........................................
[2]
(b) An alarm has been set for 07:30. Two 8-bit registers, C and D, are used to represent the
hours and minutes of the alarm time.
Show how 07:30 would be represented by these two registers:
C D
:
Hours Minutes
[2]
(c) Describe how the microprocessor can determine when to sound the clock alarm.
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© UCLES 2015 0478/11/M/J/15
, 13
(d) The LCD (liquid crystal display) on the clock face is back-lit using blue LEDs (light emitting
diodes). The brightness of the clock face is determined by the level of light in the room. The
amount of light given out by the LEDs is controlled by a control circuit.
Describe how the sensor, microprocessor and LEDs are used to maintain the correct
brightness of the clock face.
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(e) Modern LCD monitors and televisions use LED back-lit technology.
Give two advantages of using this new technology compared to the older cold cathode
fluorescent lamp (CCFL) method.
1 ................................................................................................................................................
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2 ................................................................................................................................................
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[2]
© UCLES 2015 0478/11/M/J/15 [Turn over
, QUESTION 2. 7
7 Computer A is communicating with computer B.
(a) Draw an arrow or arrows to show simplex, duplex and half-duplex data transmission. The
direction of the data transmission must be fully labelled.
Simplex data transmission
Computer A Computer B
Duplex data transmission
Computer A Computer B
Half-duplex data transmission
Computer B Computer A
[6]
(b) State a use for the following data transmission methods. The use must be different for each
data transmission method.
Simplex �������������������������������������������������������������������������������������������������������������������������������������
���������������������������������������������������������������������������������������������������������������������������������������������������
Duplex ��������������������������������������������������������������������������������������������������������������������������������������
���������������������������������������������������������������������������������������������������������������������������������������������������
[2]
© UCLES 2017 0478/12/M/J/17 [Turn over
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