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High Speed Inter-Chip USB 2.0 Hub and Flash Media Controller
Datasheet
SMSC USB4640/USB4640i 35 Revision 1.0 (06-01-09)
DATASHEET
8.4.1.17 9Ah: USB BmAttribute (1 byte)
8.4.1.18 9Bh: USB MaxPower (1 byte)
BIT NAME DESCRIPTION
7:0 USB_BM_ATT Self- or Bus-Power: Selects between self- and bus-powered operation.
The hub is either self-powered (draws less than 2 mA) or bus-powered
(limited to 100 mA maximum power prior to being configured by the host
controller).
When configured as a bus-powered device, the SMSC hub consumes less
than 100 mA of current prior to being configured. After configuration, the bus-
powered SMSC hub (along with all associated hub circuitry, any embedded
devices if part of a compound device, and 100 mA per externally available
downstream port) must consume no more than 500 mA of current. The
current consumption is system dependent, and the OEM must ensure that
the USB 2.0 Specification is not violated.
When configured as a self-powered device, <1 mA of current is consumed
and all ports are available, with each port being capable of sourcing 500 mA
of current.
80 = Bus-powered operation (default)
C0 = Self-powered operation
A0 = Bus-powered operation with remote wake-up
E0 = Self-powered operation with remote wake-up
BIT NAME DESCRIPTION
7:0 USB_MAX_PWR USB Max Power per the USB 2.0 Specification. Do NOT set this value
greater than 100 mA.