Datasheet

USB 2.0 Hi-Speed 7-Port Hub Controller
Datasheet
SMSC USB2517 19 Revision 2.8 (09-17-12)
DATASHEET
Chapter 7 Configuration Options
7.1 7-Port Hub
SMSC’s 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 operation and functionality.
For performance reasons, the 7-Port Hub provides 1 Transaction Translator (TT) per port (defined as Multi-TT
configuration), divided into 4 non-periodic buffers per TT.
7.1.1 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 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
Note: The hub will support active high power controllers only!
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 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.
7.2 EEPROM Interface
The SMSC Hub can be configured via a 2-wire (I
2
C) EEPROM (256x8). (Please see Table 5.2, "USB2517 SMBUS
or EEPROM Interface Behavior" for specific details on how to enable configuration via an I
2
C 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.
7.2.1 Internal Register Set (Common to EEPROM and SMBus)
Table 7.1 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 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