BUS SWITCHING SYSTEM FOR SERVICE PROCESSOR

摘要

PURPOSE:To attain the individual control and call-out of the internal state of an optional main body device through plural service processors SVP, by using a circuit which switches the bus of each SVP and a circuit which controls the priority of operations. CONSTITUTION:A busy flag is turned on to start an access to a main body device 1 in case no operation is executed by an access strobe signal sent from an SVP-A. An affirmative answer is sent back to the SVP-A after the end of the access. The SVP-A lost the access strobe signal and the busy flag is reset. Then an operation is kept waiting even if an SVP-B starts an access during an access of the SVP-A. Thus the priority is decided for operations between both SVP-A and B and therefore the access is possible regardless of the action mode of a system. In case the access strobe signals are transmitted at a time, a priority control circuit 32 performs the selection control so that the access is carried out in the prescribed priority.