The address bus of any microprocessor is always_____.

Question

Examoogle · Accepted Answer

Unidirectional

Explanation: The address bus in a microprocessor is always unidirectional because the processor is the sole entity responsible for generating and placing the physical address on the bus to identify a memory location or I/O port. Information flows exclusively from the CPU to the memory or peripheral devices, which then respond to the requested address.

Working Principle: The CPU uses the address bus to specify the target location in memory ($M$) or the I/O address ($I/O$) for a read or write operation. Since the microprocessor is the 'master' that initiates communication, it does not need to receive address information from memory or peripherals, making a bidirectional path unnecessary and redundant.

Key Formulas: $N = 2^n$ — where $N$ is the total addressable memory locations and $n$ is the number of address bus lines.

Key Points: Address bus width determines the maximum memory capacity of the processor.; Unidirectional flow ensures clear communication control by the CPU.; Data buses are bidirectional, whereas address buses and control buses (mostly) are unidirectional.

Advantages: Simpler control logic; Reduced hardware complexity by limiting signal direction; Prevents bus contention for address signals

Disadvantages: Limits physical communication to one-way master-to-slave operation; Cannot be used for peer-to-peer memory access without arbitration

Applications: Memory interface; I/O device selection; System control signals

Additional Info: In an 8085 microprocessor, the address bus is 16 bits wide, allowing addressing up to $2^{16} = 64$ KB.. Option B is incorrect because bidirectional buses (like data buses) allow signals to flow in both directions between CPU and memory/peripherals.

Answer: A is correct — The address bus is unidirectional because addresses are sent only from the CPU to external memory or peripherals.

Exam Tip: Always remember: Address is sent by the master (CPU) only, while data is transferred both ways; therefore, Address Bus = Unidirectional, Data Bus = Bidirectional.

Related Questions

Discussion (0)