USB 2.0 Hi-Speed Hub Controller
Datasheet
8.2.1.29
Register F8h: Boost_4:0
BIT
NUMBER
BIT NAME
DESCRIPTION
7:6
5:4
3:2
1:0
BOOST_IOUT_4
USB electrical signaling drive strength Boost Bit for Downstream Port ‘4’.
‘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)
BOOST_IOUT_3
BOOST_IOUT_2
BOOST_IOUT_1
USB electrical signaling drive strength Boost Bit for Downstream Port ‘3’.
‘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 ‘2’.
‘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 ‘1’.
‘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.
8.2.1.30
Register FAh: Port Swap
BIT
NUMBER
BIT NAME
DESCRIPTION
7:0
PRTSP
Port Swap: Swaps the Upstream and Downstream USB DP and DM Pins for
ease of board routing to devices and connectors.
‘0’ = USB D+ functionality is associated with the DP pin and D- functionality
is associated with the DM pin.
‘1’ = USB D+ functionality is associated with the DM pin and D- functionality
is associated with the DP pin.
Bit 7= Controls Port 7
Bit 6= Controls Port 6
Bit 5= Controls Port 5
Bit 4= Controls Port 4
Bit 3= Controls Port 3
Bit 2= Controls Port 2
Bit 1= Controls Port 1
Bit 0= When this bit is ‘1’, the upstream port DP/DM is swapped.
SMSC USB251x
47
Revision 1.0 (3-11-09)
DATASHEET
SMSC [ SMSC CORPORATION ]
