Question

The lowest priority usage among the following is

(a) hold request

(b) processor extension data transfer

(c) prefetch operation to fetch and arrange next instruction bytes in queue

(d) data transfer performed by EU for instruction execution

I got this question in unit test.

Enquiry is from Priority of Bus Use By 80286, Bus Hold and HLDA Sequence, Interrupt Acknowledge Sequence topic in chapter 80286-80287-A Microprocessor with Memory Management and Protection of Microprocessor

Answer 1

Right answer is (c) prefetch operation to fetch and arrange next instruction bytes in queue

The best explanation: The order of priority usages, starting from the highest one to the lowest one, is given as

1. transfer with LOCK (active low) signal

2. second byte transfer of 2-byte transfer at an odd address

3. second or third transfer cycle of a processor extension data transfer

4. HOLD request

5. processor extension data transfer

6. data transfer performed by EU (execution unit)

7. prefetch operation to fetch and arrange next instruction bytes in queue.