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1.3.4-Output-devices
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1.3.4-Output-devices
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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. 4
3 Four input devices, four descriptions and four applications are shown below.
Draw a line to connect each input device to its correct description. Then connect each description
to its correct application.
Input device Description Application
copies paper documents and
voice
barcode reader converts the text and pictures
recognition
into a computer-readable form
reads labels containing parallel
microphone dark and light lines using laser reading
light or LEDs; the width of each passports
line represents a binary code
detects changes in acidity
automatic stock
pH sensor levels; data is often in
control
analogue form
device that allows audio
signals to be converted into
monitor soil in a
scanner electric signals; these can be
greenhouse
interpreted by a computer after
being converted into digital form
[6]
© UCLES 2015 0478/12/M/J/15
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