USB2512 datasheet(34/72 Pages) SMSC

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USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 1.0 (3-11-09)

SMSC USB251x

DATASHEET

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

8.1.2.1

Power 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.

8.1.3

VBus 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.

8.2

EEPROM 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.

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

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

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

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

Table 8.1 Hub Configuration Options (continued)

CFG_SEL[2]

CFG_SEL[1]

CFG_SEL[0]

DESCRIPTION

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