When computers (or microprocessors) are used to control devices (such as robots), registers are used as part of the control system. The following example describes how registers can be used in controlling a simple device. A robot vacuum cleaner has three wheels, A, B and C. A rotates on a spindle to allow for direction changes (as well as forward and backward movement); B and C are fixed to revolve around their axles to provide only forward and backward movement, and have an electric motor attached:
Figure 1.3
An 8-bit register is used to control the movement of the robot vacuum cleaner:
Figure 1.4
If the register contains 1 0 1 0 1 0 1 0 this means ‘motor B is ON and motor C is ON and both motors are turning to produce FORWARDS motion’. Effectively, the vacuum cleaner is moving forwards.
Activity 1.3
What would be the effect if the register contained the following values?
i 1 0 0 1 1 0 0 0
ii 1 0 1 0 0 1 0 1
iii 1 0 1 0 0 1 1 0
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