Question

a. A digital computer has a common bus system for 16 registers of 8 bits each. The bus is constructed with multiplexer. How many selection inputs are there in each multiplexer? (2 Marks) b. What is the size of multiplexer? (2 Marks) How many multiplexers are there in the bus? (2 Marks) d. Illustrate this through block diagram. (11 Marks) What are the advantages of multiplexer? (3 Marks) C. e.

Answer 1

GIVEN: A common bus for 16 registers of 8 bits each constructed with multiplexer.

a) Number of selection inputs in each multiplexer:

Number of registers = 2ⁿ , where n= number of selection input lines

Here, number of registers = 16 = 2⁴

Therefore, n = 4

    Number of selection inputs in each multiplexer = 4

b) Size of multiplexer:

    Size of multiplexers = Number of registers X 1

    Here, Number of registers = 16

Therefore, Size of multiplexers = 16 X 1

c) Number of multiplexers in the bus:

    Number of multiplexers = Number of bits in each register

    Here, Number of bits in each register = 8

    Therefore, Number of multiplexers in the bus = 8

e) Advantages of multiplexer:

• Multiple circuits combinations can be implemented using multiplexer.
• It simplifies the logic design of the circuit.
• The circuit with multiplexers is less complex and the transmission cost is economical.
• No K-maps or simplification is needed in such logic designs.