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USB COMMAND DETAILS
USB_RESET D+/D- low for an extended period
USB Spec: A device may reset after seeing an SE0 for more than 18.7 uS, and de nitely after 10mS.
Notes: After power up and prior to Reset, the device will not respond to any USB commands. After the
device has been given a USB Reset, the device’s address will be reset to zero and the device will
be in the Default state. The chip will default to Report protocol and any pending output will be
ushed.
All registers will be reset to a state that matches power-on-reset with the following exceptions:
USB State register will be “Default” instead of “Attached”.
USB_SUSPEND Idle state for an extended period
USB Spec: A device may suspend after seeing an idle for more than 3mS, and de nitely after 10mS.
Notes: The chip will take a minimum of 5mS to start Suspend, though will de nitely start after 6mS.
The chip may nish the current frame if necessary before stopping the clock. Thus, an additional
frame time may be used to reach Suspend mode.
USB_RESUME Non-idle state
USB Spec: Remote Resume signalling from a device must be between 1mS and 15mS. The host is required
to send Resume signaling for 20mS plus 10mS of resume recovery time in which it does not
access any devices. This allows devices enough time to wake back up.
Notes: The chip can cause a Resume if Remote Wakeup is enabled and a button has been pressed.
Remote resume signalling from the chip will last 11.45mS to 12.45mS.
Get_Status_Device 80 00 00 00 00 00 02 00
Returns: xx yy
xx[0] = Self Powered
xx[1] = Remote Wakeup
xx[7:2] = 0
yy = 00 (Reserved)
Default: Accept (unde ned in USB Spec)
Addressed: Accept
Con gured: Accept
Notes: Use Set_Feature_Device/Clear_Feature_Device to set/clear remote wakeup.
Get_Status_Interface 81 00 00 00 00 00 02 00
Returns: 00 00
Default: Stall (unde ned in USB Spec)
Addressed: Stall
Con gured: Accept
Notes: Both return bytes are reserved and currently 00.
