USB 2.0 Hi-Speed Hub Controller

 

 

 

 

Datasheet

 

Table 8.1 Hub Configuration Options (continued)

 

 

 

 

 

 

CFG_SEL[2]

CFG_SEL[1]

CFG_SEL[0]

 

DESCRIPTION

 

 

 

 

 

 

1

0

0

Internal Default Configuration with the following over-rides

 

 

 

 

„

Dynamic power-switching enabled

 

 

 

 

„

Strap options disabled

 

 

 

 

„

LED mode = Speed (when available on package)

 

 

 

 

„

Individual power switching

 

 

 

 

„

Individual over-current sensing

 

 

 

 

 

 

1

0

1

Internal Default Configuration with the following over-rides

 

 

 

 

„

Dynamic setting enabled

 

 

 

 

„

Strap options disabled

 

 

 

 

„

LED mode = USB (when available on package)

 

 

 

 

„

Individual power switching

 

 

 

 

„

Individual over-current sensing

 

 

 

 

 

 

1

1

0

Internal Default Configuration with the following over-rides

 

 

 

 

„

Strap options disabled

 

 

 

 

„

LED mode = Speed (when available on package)

 

 

 

 

„

Individual power switching

 

 

 

 

„

Individual over-current sensing

 

 

 

 

 

 

1

1

1

Internal Default Configuration with the following over-rides

 

 

 

 

„ Strap options disabled

 

 

 

 

„ LED mode = USB (when available on package)

 

 

 

 

„ Ganged port power switching

 

 

 

 

„ Ganged over-current sensing

 

 

 

 

 

 

 

Note: When the CFG_SEL[2] pin is unavailable, then the logic is internally tied to ‘0’.

8.1.2.1Power Switching Polarity

When the PRTPWR_POL pin is unavailable (3 and 4 port, 48-pin packages only), the hub only supports “active high” port power controllers.

8.1.3VBus Detect

According to Section 7.2.1 of the USB 2.0 specification, a downstream port can never provide power to its D+ or D- pull-up resistors unless the upstream port’s VBUS is in the asserted (powered) state. The VBUS_DET pin on the hub monitors the state of the upstream VBUS signal and will not pull-up the D+ resistor if VBUS is not active. If VBUS goes from an active to an inactive state (Not Powered), the hub will remove power from the D+ pull-up resistor within 10 seconds.

8.2EEPROM Interface

The SMSC hub can be configured via a 2-wire (I2C) EEPROM (256x8). (Please see Table 8.1, "Hub Configuration Options" for specific details on how to enable configuration via an I2C EEPROM).

The internal state-machine will (when configured for EEPROM support) read the external EEPROM for configuration data. The hub will then “attach” to the upstream USB host.

Note: The hub does not have the capacity to write, or “Program,” an external EEPROM. The hub only has the capability to read external EEPROMs. The external eeprom will be read (even if it is blank or non-populated), and the hub will be “configured” with the values that are read.

Revision 1.0 (3-11-09)

34

SMSC USB251x

DATASHEET