USB 2.0 High-Speed 4-Port Hub Controller
Datasheet
Revision 1.98 (11-19-07)
30
SMSC USB2514
DATASHEET
4.3.1.27
Register F8h: Boost_4:0
BIT
NUMBER
BIT NAME
DESCRIPTION
7:6
BOOST_IOUT_4
Upstream USB electrical signaling drive strength Boost Bit for Downstream
Port ‘4’.
‘00’ = Normal electrical drive strength = No boost
‘01’ = Elevated electrical drive strength = Low (approximately 4% boost)
‘10’ = Elevated electrical drive strength = Medium (approximately 8% boost)
‘11’ = Elevated electrical drive strength = High (approximately 12% boost)
Note:
“Boost” could result in non-USB Compliant parameters (one
example would be Test J/K levels), the OEM should use a ‘00’
value unless specific implementation issues require additional
signal boosting to correct for degraded USB signalling levels.
5:4
BOOST_IOUT_3
Upstream USB electrical signaling drive strength Boost Bit for Downstream
Port ‘3’.
‘00’ = Normal electrical drive strength = No boost
‘01’ = Elevated electrical drive strength = Low (approximately 4% boost)
‘10’ = Elevated electrical drive strength = Medium (approximately 8% boost)
‘11’ = Elevated electrical drive strength = High (approximately 12% boost)
Note:
“Boost” could result in non-USB Compliant parameters (one
example would be Test J/K levels), the OEM should use a ‘00’
value unless specific implementation issues require additional
signal boosting to correct for degraded USB signalling levels.
3:2
BOOST_IOUT_2
Upstream USB electrical signaling drive strength Boost Bit for Downstream
Port ‘2’.
‘00’ = Normal electrical drive strength = No boost
‘01’ = Elevated electrical drive strength = Low (approximately 4% boost)
‘10’ = Elevated electrical drive strength = Medium (approximately 8% boost)
‘11’ = Elevated electrical drive strength = High (approximately 12% boost)
Note:
“Boost” could result in non-USB Compliant parameters (one
example would be Test J/K levels), the OEM should use a ‘00’
value unless specific implementation issues require additional
signal boosting to correct for degraded USB signalling levels.
1:0
BOOST_IOUT_1
Upstream USB electrical signaling drive strength Boost Bit for Downstream
Port ‘1’.
‘00’ = Normal electrical drive strength = No boost
‘01’ = Elevated electrical drive strength = Low (approximately 4% boost)
‘10’ = Elevated electrical drive strength = Medium (approximately 8% boost)
‘11’ = Elevated electrical drive strength = High (approximately 12% boost)
Note:
“Boost” could result in non-USB Compliant parameters (one
example would be Test J/K levels), the OEM should use a ‘00’
value unless specific implementation issues require additional
signal boosting to correct for degraded USB signalling levels.