PROTECTING METHOD FOR SHARED MEMORY DEVICE, ACCESS SUPPRESSION/RELEASE MECHANISM, AND STARTING SELF-DIAGNOSTIC REPORT MECHANISM

摘要

PURPOSE:To surely protect a shared memory even with the on-line maintenance by holding the operation stop information on a CPU in a shared memory device and suppressing the accesses given from the CPU until a specific code is received with confirmation of a normal operation after the start of working. CONSTITUTION:A power supply 52 reports the discontinuation of each operation of CPU 5 - 7 to a shared memory device 1 based on the operation discontunation information 521. An executing unit 54 diagnoses whether the operation of each CPU is normal or not when the CPU operation is started and outputs a specific code to the device 1 when the normal operation is confirmed. These power supply 52 and unit 54 are provided on each of CPU 5 - 7. Then the operation stop information received from each CPU is held in the device 1. Furthermore the means 2 - 4 are provided to suppress the write accesses 55 received from those CPUs before a specific code is received from the CPU and the operation stop information is cleared. In such a constitution, it is possible to avoid such a case where the data to be given to the device 1 are destroyed by a malfunction caused when the maintenance is secured to each CPU and the operation of each CPU is started.