A-LevelComputer ScienceHardware9618/12 · Oct/Nov 2022 · Q37 Marks

A greenhouse has an automatic window. The window (X) operates according to the following criteria: [Table: Parameter, Description of parameter, Binary value, Condition (T: Temperature, W: Wind speed, R: Rain, M: Manual override, with corresponding binary values and conditions)] The window opens (X = 1) if: • the temperature is too high and the wind speed is acceptable and • rain is not detected, or the manual override is off.

(a)Draw a logic circuit to represent the operation of the window.[3]
(b)Complete the truth table for the logic expression: X = NOT (A OR B OR C) AND (B NOR C) [Table: A, B, C, Working space, X][2]
(c)Embedded systems contain Read Only Memory (ROM) and Random Access Memory (RAM). Explain the reasons why ROM is used in an embedded system.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

[1] T AND NOT W
[1] NOT R OR NOT M
[1] final AND
[1] A B C | X : 0 0 0 | 1
[1] A B C | X : 0 0 1 | 0, 0 1 0 | 0, 0 1 1 | 0, 1 0 0 | 0, 1 0 1 | 0, 1 1 0 | 0, 1 1 1 | 0
[1] to store data that does not change
[1] data must be stored even when device is without power
[1] to store boot up instructions / system software / firmware / BIOS

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