Potential Communication Problems With Usb Devices - Epson S1R72U16 Support Manual

4.3.3

Potential Communication Problems with USB Devices

This section describes communication problems with USB devices that can be inferred
from history data.
If the following history data appears, the current drawn from the VBUS by the USB device
may exceed the supply capacity.
• "USB: VBUS overcurrent"
If the following history data appears, there may be a problem in the USB device.
• "USB: phase err"
If the USB storage device continues to return NAK, the following history data will appear.
As the LSI is executing commands, timeout processing should be performed and an
ATA/ATAPI standard reset should be issued by the main CPU.
• "USB: CBW" appears in the history, but "USB: CSW" does not, with no status
• "USB: Mass Storage Reset" or "USB: cleared STALL" appears at the end of the history,
If the following combinations appear in the history data, there may be a conflict in the
protocol between the USB host and the device. In this case, since an error status is returned
to the main CPU, the error should be processed appropriately at the main CPU. If this state
occurs other than when a command is being executed (Status register BSY bit is 1 or DRQ
bit is 1), the USB device involved will be treated as an unsupported device.
• "USB: cleared STALL" – "USB: Mass Storage Reset" appear in history.
• "USB: phase err" – "USB: Mass Storage Reset" appear in history.
S1R72U16 Development
Support Manual (Rev.2.00)
changes.
without any subsequent changes.
EPSON
4. History Data Details
15