USB2517 datasheet(19/58 Pages) MICROCHIP

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DS00001598B-page 19

USB2517/USB2517I

7.0

CONFIGURATION OPTIONS

7.1

7-Port Hub

The USB 2.0 7-Port Hub is fully compliant to the Universal Serial Bus Specification Revision 2.0 from April 27, 2000 (12/

7/2000 and 5/28/2002 Errata). Please reference Chapter 11 (Hub Specification) for general details regarding Hub oper-

ation and functionality.

For performance reasons, the 7-Port Hub provides 1 Transaction Translator (TT) per port (defined as Multi-TT configu-

ration), divided into 4 non-periodic buffers per TT.

7.1.1

HUB CONFIGURATION OPTIONS

The MCHP 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 overrides). In all cases, the configuration

method will be determined by the CFG_SEL2, CFG_SEL1 and CFG_SEL0 pins immediately after RESET_N negation.

7.1.1.1

Power Switching Polarity

7.1.2

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 mon-

itors 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.

7.2

EEPROM Interface

The MCHP Hub can be configured via a 2-wire (I2C) EEPROM (256x8). (Please see Table 5-2, "USB2517I SMBUS or

EEPROM Interface Behavior" 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.

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

7.2.1

INTERNAL REGISTER SET (COMMON TO EEPROM AND SMBUS)

Note:

The hub will support active high power controllers only!

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-popu-

lated), and the Hub will be “configured” with the values that are read.

TABLE 7-1:

INTERNAL DEFAULT, EEPROM AND SMBUS REGISTER MEMORY MAP

Reg Addr

R/W

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

17h

0x00

03h

R/W

PID MSB

PIDM

25h

0x00

04h

R/W

DID LSB

DIDL

00h

0x00

05h

R/W

DID MSB

DIDM

00h

0x00

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