Question

What is the limiting factor in determining how many input/output ports a processor can access?

A: the number of bits allocated to a port instruction

B: the number of bits in the port address

C: the number of bits supported by the data bus D:

the number of bits supported by the address bus

E: There are no limiting factors

Answer 1

• The limiting factor in determining how many input/output ports a processor can access is :

B. The number of bits in the port addess.
Because, if a processor generates x bit I/O port address, then it can access 2^x I/O ports. For example, 8086 can generate 16 bit I/O address, so it can access 2^16 I/O ports.

• Following factors cannot determine that how many I/O ports a processor can access.

A. The number of bits allocated to port instruction
C. The number of bits supported by data bus
D. The number of bits supported by address bus
E. There are no limiting factors

The size of instruction is determined by size of opcode and operand. It doesn't affect the processor'saccess to I/O ports. The data bus is responsible for transmission of data in the system, so it cannot affect prosessor accessing I/O ports. Thee address bus is responsible for carrrying addressing signals from processor to memory, IO and other peripherals. Hence, these factors cannot determine that how many I/O ports processor can access.