Selective control of power supply to pull up circuits for bus signal lines

摘要

A power supply control enables or disables the supply of power to the pull up circuits 510 of a bus 402, such as a compact PCI bus. Each line 502 of the bus is connected to a separate pull up circuit, preferably a resistor. The circuits are isolated from each other, preferably using diodes 512. In a first mode, the power supply powers the pull up circuits. In a second mode, no power is provided. The mode may be changed in response to a signal 508 on the bus. The power supply may comprise a voltage regulator 514 with an enable input 524 connected to the signal. Alternatively, the power supply may be disabled using a switch that disconnects it from the pull up circuits. The device may be used with a bridge unit 504 that connects the bus to a second bus 404 in response to the enable signal.