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Spinpoint M8U-Internal Product Manual REV 3.4
61
INSTALLATION
that configuration is the maximum the device will draw from VBUS in either mode.
The device must observe this maximum, regardless of its mode. If a configuration supports only one power
mode and the power source of the device changes, the device will lose its current configuration and address
and return to the Powered state. If a device is self-powered and its current configuration requires more than
100 mA, then if the device switches to being bus-powered, it must return to the Address state. Self-powered
hubs that use V
BUS to power the Hub Controller are allowed to remain in the Configured state if local power
is lost.
A hub port must be powered in order to detect port status changes, including attach and detach. Bus powered
hubs do not provide any downstream power until they are configured, at which point they will provide power
as allowed by their configuration and power source. A USB device must be able to be addressed within a
specified time period from when power is initially applied. After an attachment to a port has been detected,
the host may enable the port, which will also reset the device attached to the port.
6.3.6.1.3 Default
After the device has been powered, it must not respond to any bus transactions until it has received a reset
from the bus. After receiving a reset, the device is then addressable at the default address.
When the reset process is complete, the USB device is operating at the correct speed (i.e., low-/full-
/highspeed).
The speed selection for low- and full-speed is determined by the device termination resistors. A device that is
capable of high-speed operation determines whether it will operate at high-speed as a part of the reset process
A device capable of high-speed operation must reset successfully at full-speed when in an electrical
environment that is operating at full-speed. After the device is successfully reset, the device must also
respond successfully to device and configuration descriptor requests and return appropriate information.
The device may or may not be able to support its intended functionality when operating at full-speed.
6.3.6.1.4 Address
All USB devices use the default address when initially powered or after the device has been reset. Each USB
device is assigned a unique address by the host after attachment or after reset. A USB device maintains its
assigned address while suspended.
A USB device responds to requests on its default pipe whether the device is currently assigned a unique
address or is using the default address.
6.3.6.1.5 Configured
Before a USB device’s function may be used, the device must be configured. From the device’s perspective,
configuration involves correctly processing a SetConfiguration () request with a non-zero configuration value.
Configuring a device or changing an alternate setting causes all of the status and configuration values
associated with endpoints in the affected interfaces to be set to their default values.
This includes setting the data toggle of any endpoint using data toggles to the value DATA0.
6.3.6.1.6 Suspended
In order to conserve power, USB devices automatically enter the Suspended state when the device has
observed no bus traffic for a specified period. When suspended, the USB device maintains any internal status,
including its address and configuration.
All devices must suspend if bus activity has not been observed for the length of time. Attached devices must
be prepared to suspend at any time they are powered, whether they have been assigned a non-default address
or are configured. Bus activity may cease due to the host entering a suspend mode of its own. In addition, a
USB device shall also enter the Suspended state when the hub port it is attached to is disabled. This is
referred to as selective suspend.
A USB device exits suspend mode when there is bus activity. A USB device may also request the host to exit
suspend mode or selective suspend by using electrical signaling to indicate remote wakeup. The ability of a
device to signal remote wakeup is optional. If a USB device is capable of remote wakeup signaling, the
device must support the ability of the host to enable and disable this capability. When the device is reset,