| 摘要 |
PURPOSE:To prevent a bus line from the ON/OFF operation of a power source by installing a bus line connected to I/O device interfaces, a bypass line and relays in one unit case. CONSTITUTION:Input/output device interfaces IF401 and 402, a bus line BL403 to which IFs are connected, a bypass line BPL405, and relays 406 and 407 are installed in a unit case 400. When a power source 404 is turned on, voltage Vcc1 is generated and applied to the IFs 401 and 402 and the relays 406 and 407. At the rise of voltage Vcc1, the relays 406 and 407 turn switches SWs 408 and 409 to the BPL405 side respectively and the external BL410 is connected to the BLP405. When voltage Vcc2 is fed from the power source to the relays 406 and 407 after passing DELTAT from the rise of Vcc1, the relays turn SWs 408 and 409 to the BL403 side and connect the BL403 to the BL410 to hold the relays at voltage Vcc2. When power supply is cut off, voltage Vcc2 drops and, after changing over SWs to the BPL405, voltage Vcc1 also drops, so that the BL is not influenced by the ON/OFF operation of the power source. |
