| 摘要 |
PURPOSE:To save the signal line by allowing a processing unit to use a data line and sending a system selection signal to a low-order equipment in a system selection system in a system having a processing unit taking especially as the duplicated constitution with respect to the data communication system. CONSTITUTION:With the system 0 set in the act system and the system 1 set in the standby system, when a 0 system processing unit 1 accesses a low-order device 5, system designation information is given to a specific bit in data bits to send a data to a 0 system bus 3. On the other hand, when the low-order device 5 receives a data, the device 5 discriminates that the system 0 is the act system to throw a system changeover switch 9 in a way that the data of 0 system is enabled. With the system 0 set in the standby system and the system 1 set in the act system conversely, the device 5 discriminates that the system 1 is the act system to throw the system changeover switch 9 in a way that the data of 1 system is enabled. |
