A digital computer has a common bus system for 8 registers 16 bits each. How…
2021
A digital computer has a common bus system for 8 registers 16 bits each. How many multiplexers are required to implement common bus? What size of multiplexers is required?
- A.
16, 8x1
- B.
8, 16x1
- C.
8, 8x1
- D.
16, 16x1
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Correct answer: A
Answer: 16 multiplexers, each 8-to-1.
Explanation:
There are 8 registers and each register is 16 bits wide, so the common bus is 16 bits wide.
For each bit position of the 16-bit bus you must select that bit from one of the 8 registers.
Therefore you need 16 separate multiplexers (one per bit), and each multiplexer must select from 8 inputs, so each is an 8-to-1 multiplexer.
Optional detail: each 8-to-1 multiplexer requires 3 selection lines because 2^3 = 8.
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