Electronics Engineering (ELEX) Board Practice Exam

What is the correct sequence of operations in a microprocessor?

1. Memory read, I/O write, I/O read, opcode fetch, memory write

2. Opcode fetch, memory write, memory read, I/O write, I/O read

3. Opcode fetch, memory read, memory write, I/O read, I/O write

4. I/O read, opcode fetch, memory read, I/O write, memory write

The correct answer is: Opcode fetch, memory read, memory write, I/O read, I/O write

The correct sequence of operations in a microprocessor involves a systematic approach to executing instructions. In option C, the sequence begins with an opcode fetch, which is essential as it allows the microprocessor to retrieve the instruction that needs to be executed. This is the foundational step that informs the microprocessor about what operation it should perform. Following the opcode fetch, the next operation is memory read. This step is crucial when the instruction requires data from memory. Once the necessary data is accessed, the microprocessor can perform the required operations, which may include memory write if results need to be stored back into memory. Then, if the instruction interacts with input/output devices, it can proceed with I/O read, where data is read from an external device, and finally, it may execute an I/O write operation to send data to an external device. This sequence highlights the logical flow of instruction execution: fetching the instruction, retrieving any necessary data, performing operations on that data, and then handling any required I/O operations. By following this structured process, the microprocessor maintains efficiency and accuracy in instruction processing.