| 摘要 |
<p>An expansion port (35) for a processing system peripheral device provides for a system power down prior to connection of another device to the port. A number of devices (10, 30) in a processing system are connected in a daisy chain. One of the devices (10) includes a power supply (40) for supplying power to each of the devices (30). Each of the devices (30) includes a segment (PWR.DIS.1 and PWR.DIS.2) of an enable circuit for enabling or disabling the power supply (40). Each of the devices (30) further includes an expansion port (35) for connecting the enable circuit and other signals to another device (10, 30) in the daisy chain. An access panel (38) is provided to cover the expansion port (35) when the port (35) is not in use. When the access panel (38) is closed a switch (32) located at the expansion port (35) and coupled to the enable circuit of the device (30) is actuated in order to enable the power supply (40). When the access panel (38) is not in place and no other device (10, 30) is connected to the expansion port (35), the switch (37) is in a different position which causes the power supply (41) to be disabled. If another device (10, 30) is properly connected to the expansion port (35), then the switch (37) is in the first position to cause the power supply (41) to be enabled, provided all other devices (10, 30) in the daisy chain are also properly connected. Accordingly, removal of an access panel (38) on one of the devices (10, 30) while power to the system is on causes power to the system to be removed before another device (10, 30) can be connected to the expansion port (35), thus preventing damaging electrical transients from occurring upon connection to the expansion port (35).</p> |
