Samsung ST750LM024 User Manual
Spinpoint M8U-Internal Product Manual REV 3.4
64
INSTALLATION
device, Host Software shall not select that configuration.
USB devices shall limit the power they consume from V
USB devices shall limit the power they consume from V
BUS
to one unit load or less until configured.
Suspended devices, whether configured or not, shall limit their bus power consumption. Depending on the
power capabilities of the port to which the device is attached, a USB device may be able to draw up to five
unit loads from V
power capabilities of the port to which the device is attached, a USB device may be able to draw up to five
unit loads from V
BUS
after configuration.
■ Remote WakeUp
Remote wakeup allows a suspended USB device to signal a host that may also be suspended. This notifies the
host that it should resume from its suspended mode, if necessary, and service the external event that triggered
the suspended USB device to signal the host. A USB device reports its ability to support remote wakeup in a
configuration descriptor. If a device supports remote wakeup, it must also allow the capability to be enabled
and disabled using the standard USB requests.
Remote wakeup allows a suspended USB device to signal a host that may also be suspended. This notifies the
host that it should resume from its suspended mode, if necessary, and service the external event that triggered
the suspended USB device to signal the host. A USB device reports its ability to support remote wakeup in a
configuration descriptor. If a device supports remote wakeup, it must also allow the capability to be enabled
and disabled using the standard USB requests.
6.3.6.2.6
Request Processing
With the exception of SetAddress () requests, a device may begin processing of a request as soon as the
device returns the ACK following the Setup. The device is expected to “complete” processing of the request
before it allows the Status stage to complete successfully. Some requests initiate operations that take many
milliseconds to complete. For requests such as this, the device class is required to define a method other than
Status stage completion to indicate that the operation has completed. For example, a reset on a hub port takes
at least 10 ms to complete. The SetPortFeature (PORT_RESET) request “completes” when the reset on the
port is initiated. Completion of the reset operation is signaled when the port’s status change is set to indicate
that the port is now enabled
device returns the ACK following the Setup. The device is expected to “complete” processing of the request
before it allows the Status stage to complete successfully. Some requests initiate operations that take many
milliseconds to complete. For requests such as this, the device class is required to define a method other than
Status stage completion to indicate that the operation has completed. For example, a reset on a hub port takes
at least 10 ms to complete. The SetPortFeature (PORT_RESET) request “completes” when the reset on the
port is initiated. Completion of the reset operation is signaled when the port’s status change is set to indicate
that the port is now enabled
6.3.6.3
Standard USB Device Requests
All USB devices respond to requests from the host on the device’s Default Control Pipe. These requests are
made using control transfers. The request and the request’s parameters are sent to the device in the Setup
packet. The host is responsible for establishing the values passed in the fields listed in Table 6-5. Every Setup
packet has eight bytes.
made using control transfers. The request and the request’s parameters are sent to the device in the Setup
packet. The host is responsible for establishing the values passed in the fields listed in Table 6-5. Every Setup
packet has eight bytes.
Table 6-5: Format of Setup Data