Consider an I/O device that uses the vectored-interrupt capability of the 68000 processor.

(a) Describe the sequence of steps that take place when the processor receives an interrupt request, and give the number of bus transfers required during each of these steps. Do not give details of bus signals or the microprogram.

(b) When an interrupt request is received, the processor completes execution of the current instruction before accepting the interrupt. Examine the instruction table in Appendix C, and estimate the maximum possible number of memory transfers that can take place during that period.

(c) Estimate the number of bus transfers that can occur from the instant a device requests an interrupt until the first instruction of the interrupt-service routine is fetched for execution.