| 摘要 |
PURPOSE:To attain a simplified bus extension method by subjecting the power supply line of a computer and that of an extended input/output device to wired OR connection and using them for power supply to both bus interfaces. CONSTITUTION:Power supply lines VIF subjected to wired OR connection by diodes D1 and D2 are used for power supply to a bus interface part 5 of a basic part A and a bus interface part 7 of an extended input/output part B. Then, power passing power supply lines VIF is supplied stably to the bus interface part 5 or 7 even if a power source VCC1 or VCC2 is turned off. The basic part A and the extended input/output part B are provided with voltage detecting circuits VC1 and VC2 which detect fall of voltages of power sources VCC1 and VCC2; and when voltages of power sources fall, inhibiting signals DS1 and DS2 which hold busses 4 and 8 in the high-impedance state are generated for the purpose of preventing unnecessary currents from flowing out to these busses. |
