Отправлено иа 27 января 2004 г. 19:49 В ответ на: Всё очень просто отправлено a123 27 января 2004 г. 19:38

The host and all self-powered hubs must implement over-current protection for safety reasons, and the hub must
have a way to detect the over-current condition and report it to the USB software. Should the aggregate current
drawn by a gang of downstream facing ports exceed a preset value, the over-current protection circuit removes
or reduces power from all affected downstream facing ports. The over-current condition is reported through the
hub to Host Controller, as described in Section 11.12.5. The preset value cannot exceed 5.0 A and must be
sufficiently above the maximum allowable port current such that transient currents (e.g., during power up or
dynamic attach or reconfiguration) do not trip the over-current protector. If an over-current condition occurs on
any port, subsequent operation of the USB is not guaranteed, and once the condition is removed, it may be
necessary to reinitialize the bus as would be done upon power-up. The over-current limiting mechanism must be
resettable without user mechanical intervention. Polymeric PTCs and solid-state switches are examples of
methods, which can be used for over-current limiting.