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.

1. (a)Identify what time is represented by the following two 8-bit registers. A 128 64 32 16 8 4 2 1 0 0 0 1 0 0 1 0 : B 128 64 32 16 8 4 2 1 0 0 1 1 0 1 0 1 Hours ........................................................ Minutes ........................................................[2]
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]
3. (c)Describe how the microprocessor can determine when to sound the clock alarm.[3]
4. (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.[3]
5. (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 2[2]

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