Question: Like most microprocessors. the 68000 uses special-purpose control lines to augment the data transfer bus. These control lines include ECU to K2. BR*, etc., IPLO* to IPL2*. etc. An alternative approach is to employ a message bus that carries encoded system control messages; for example, a device requiring attention may inject a suitable message onto this bus. Devise a method of implementing such an arrangement in a 68000-based environment. Note that a suitable protocol is needed to determine which device may access the message bus. This situation can be achieved by using a special-purpose control line or by time-division multplexing. The IEEE-488 bus has some of the characteristics of this type of control bus.