Section 18.6
Review Questions
Multiplexing

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1. Why is multiplexing needed?

answer...
because there aren't enough physical ports available for the huge number of peripherals that people want to connect to their CPUs... there just aren't enough contact pads on the chips

2. Show were the multiplexor is in the following picture.

answer...

3. Which kind of multiplexing lets the port be used by a specific peripheral for a while, and then gives control of it to a different one for another chunk of time?

answer...
time division multiplexing

4. What must be the speed characteristics of such a system in order to make this work?

answer...
the CPU and multiplexor must be faster than the peripherals

5. What does round robin mean?

answer...
the peripherals get control of the ports in a circular fashion in time, one after the other, returning to the first one eventually

6. How does statistical multiplexing work?

answer...
devices identify themselves with an id number which is attached to every command and every response

7. Why is statistical multiplexing often better?

answer...
if only one peripheral is communicating with the CPU, it will not have to wait for the empty time slots of the other peripherals before it can resume communication with the CPU