USB 2.0 High-Speed 2-Port Hub Controller

Datasheet

SMSC USB2512

13

Revision 1.92 (11-28-07)

DATASHEET

Chapter 4 Configuration Options

4.1

2-Port Hub

SMSC’s USB 2.0 2-Port Hub is fully specification compliant to the Universal Serial Bus Specification

Revision 2.0 April 27,2000 (12/7/2000 and 5/28/2002 Errata). Please reference Chapter 10 (Hub

Specification) for general details regarding Hub operation and functionality.

The 2-Port Hub provides 1 Transaction Translator (TT) that is shared by both downstream ports

(defined as Single-TT configuration), The TT contains 4 non-periodic buffers.

4.1.1

Hub Configuration Options

The SMSC Hub supports a large number of features (some are mutually exclusive), and must be

configured in order to correctly function when attached to a USB host controller. There are three

principal ways to configure the hub: SMBus, EEPROM, or by internal default settings (with or without

pin strapping option over-rides). In all cases, the configuration method will be determined by the

CFG_SEL1 and CFG_SEL0 pins immediately after RESET_N negation.

4.1.1.1

Power Switching Polarity

The hub only supports “active high” port power controllers.

4.1.2

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),

Hub will remove power from the D+ pull-up resistor within 10 seconds.

4.2

EEPROM Interface

The SMSC Hub can be configured via a 2-wire (I2C) EEPROM (256x8). (Please see Table 3.1 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.

Please see Internal Register Set (Common to EEPROM and SMBus) for a list of data fields available.

4.2.1

Internal Register Set (Common to EEPROM and SMBus)

Table 4.1 Internal Default, EEPROM and SMBus Register Memory Map

REG

ADDR

R/W

REGISTER NAME

ABBR

INTERNAL

DEFAULT ROM

SMBUS AND

EEPROM POR

VALUES

00h

R/W

VID LSB

VIDL

24h

0x00

01h

R/W

VID MSB

VIDM

04h

0x00

02h

R/W

PID LSB

PIDL

12h

0x00