USB 2.0 Hi-Speed Hub Controller
Datasheet
8.2.1.28
Register F7h: Boost_7:5
BIT NAME
BIT
NUMBER
DESCRIPTION
7:6
5:4
Reserved
Reserved
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
1:0
BOOST_IOUT_6
BOOST_IOUT_5
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)
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)
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.
Revision 1.0 (3-11-09)
46
SMSC USB251x
DATASHEET
SMSC [ SMSC CORPORATION ]
