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USB 2.0 Hi-Speed Hub Controller
Datasheet
SMSC USB251x 45 Revision 1.0 (3-11-09)
DATASHEET
8.2.1.25 Register 92h-CFh: Serial String
8.2.1.26 Register D0h: Battery Charging Enable
8.2.1.27 Register F6h: Boost_Up
BIT
NUMBER BIT NAME DESCRIPTION
7:0 SER_STR Serial String, UNICODE UTF-16LE per USB 2.0 specification
When supported, the maximum string length is 31 characters (62 bytes).
Note: The string consists of individual 16-bit UNICODE UTF-16LE
characters. The Characters will be stored starting with the LSB at
the least significant address and the MSB at the next 8-bit location
(subsequent characters must be stored in sequential contiguous
address in the same LSB, MSB manner). Some EEPROM
programmers may transpose the MSB and LSB, thus reversing the
Byte order. Please pay careful attention to the Byte ordering or
your selected programming tools.
BIT
NUMBER BIT NAME DESCRIPTION
7:0 BC_EN Only available in USB251xB/Bi hub family products.
Battery Charging Enable: Enables the battery charging feature for the
corresponding port.
'0' = Battery Charging support is not enabled
'1' = Battery charging support is enabled
Bit 7= Reserved
Bit 6= Reserved
Bit 5= Reserved
Bit 4= Controls Port 4
Bit 3= Controls Port 3
Bit 2= Controls Port 2
Bit 1= Controls Port 1
Bit 0= Reserved
BIT
NUMBER BIT NAME DESCRIPTION
7:2 Reserved Reserved
1:0 BOOST_IOUT USB electrical signaling drive strength Boost Bit for the Upstream Port.
‘00’ = Normal electrical drive strength = No boost
‘01’ = Elevated electrical drive strength = Low (~ 4% boost)
‘10’ = Elevated electrical drive strength = Medium (~ 8% boost)
‘11’ = Elevated electrical drive strength = High (~12% boost)
Note: “Boost” could result in non-USB Compliant parameters, OEM
should use a ‘00’ value unless specific implementation issues
require additional signal boosting to correct for degraded USB
signalling levels.