Industrial Temperature Rated USB 2.0 Hi-Speed 2-Port Hub Controller

Datasheet

Chapter 4 Configuration Options

4.12-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.

4.1.1Hub 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.

4.1.1.1Power Switching Polarity

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

4.1.2VBus 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.

4.2EEPROM 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.

4.2.1Internal Register Set (Common to EEPROM and SMBus)
Table 4.1 Internal Default, EEPROM and SMBus Register Memory Map

 

 

 

 

 

SMBUS AND
REG

 

 

 

INTERNAL
EEPROM OR
ADDR

R/W

REGISTER NAME
ABBR
DEFAULT ROM
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

 

 

 

 

 

 

SMSC USB2512Ai

13

Revision 1.97 (08-11-08)

 

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