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USB 2.0 Hi-Speed Hub Controller
Datasheet
Revision 1.0 (3-11-09) 46 SMSC USB251x
DATASHEET
8.2.1.28 Register F7h: Boost_7:5
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.
BIT
NUMBER BIT NAME DESCRIPTION
7:6 Reserved Reserved
5:4 BOOST_IOUT_7 USB electrical signaling drive strength Boost Bit for Downstream Port ‘7’.
‘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)
3:2 BOOST_IOUT_6 USB electrical signaling drive strength Boost Bit for Downstream Port ‘6’.
‘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)
1:0 BOOST_IOUT_5 USB electrical signaling drive strength Boost Bit for Downstream Port ‘5’.
‘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)