Monday, June 11, 2007

Không nhận được USB khi standby or hibernation

A USB device is not recognized if you attach it immediately after your Windows XP-based computer comes out of standby or hibernation


SYMPTOMS

When you plug a USB device into your Microsoft Windows XP-based computer immediately after the computer comes out of standby (S3) or hibernate (S4), the computer may not recognize the USB device. When this issue occurs, the USB device may or may not be listed in Device Manager as an unknown device, and you may or may not receive the following warning message:
Unrecognized device has been found.

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CAUSE

This issue occurs because, when the computer comes out of S3 or S4, there is a five- to ten-second period when the selective suspend feature of the USB driver will interfere with detection of a new USB device connection. The time period depends on several factors, including the following:
Host controller hardware
Attached hubs
Attached devices
USB driver versions
Support for USB 2.0
Additional system hardware or configurations that may change the timing

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WORKAROUND

To work around this issue, use one of the following methods:

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Method 1

After the computer comes out of S3 or S4, wait five to ten seconds before you plug the USB device into the computer or hub.

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Method 2

After the computer comes out of S3 or S4, unplug the USB device, and then plug the device back into the computer or hub.

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Method 3

Use the Device Manager to scan for new hardware. Follow these steps:
1.Click Start, and then click Run.
2. Type Devmgmt.msc in the Open box, and then click OK.
3. On the Action menu, click Scan for hardware changes. This causes Windows to recognize new devices.
4. Close Device Manager and Control Panel.

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Method 4

Disable power management of the USB hub.

Note If you perform the following procedure, you may also reduce the battery life on a portable computer.

To disable power management on the USB hub, follow these steps:
1.Click Start, and then click Run.
2. Type devmgmt.msc in the Open box, and then click OK.
3. Expand the Universal Serial Bus controllers node, and then follow these steps for each USB Root Hub that is listed:
a. Right-click the USB Root Hub, and then click Properties.
b. Click the Power Management tab.
c. Click to clear the Allow the computer to turn off this device to save power check box, and then click OK.

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STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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