High Speed Inter-Chip USB 2.0 Hub and Flash Media Controller

 

 

Datasheet

8.4.4.18

EFh: Boost_Up

 

 

 

 

BIT

NAME

DESCRIPTION

 

 

 

7:2

Reserved

Reserved

 

 

 

1:0

BOOST_IOUT

USB electrical signaling drive strength boost bit for the upstream port ‘A’.

 

 

‘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. OEM

 

 

should use a ‘00’ value unless specific implementation issues

 

 

require additional signal boosting to correct for degraded USB

 

 

signaling levels.

 

 

 

8.4.4.19F0h: Boost_3:0

BIT

NAME

DESCRIPTION

 

 

 

7:6

Reserved

Reserved

 

 

 

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)

 

 

 

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. OEM

 

 

should use a ‘00’ value unless specific implementation issues

 

 

require additional signal boosting to correct for degraded USB

 

 

signaling levels.

 

 

 

1:0

Reserved

Always reads ‘0’.

 

 

 

Revision 1.0 (06-01-09)

46

SMSC USB4640/USB4640i

DATASHEET