USB 2.0 Hi-Speed Hub Controller
Datasheet
8.2.1.35
Register FFh: Status/Command
BIT NAME
BIT
NUMBER
DESCRIPTION
7:3
2
Reserved
Reserved
INTF_PW_DN
SMBus Interface Power Down
‘0’ = Interface is active
‘1’ = Interface power down after ACK has completed
1
0
RESET
Reset the SMBus Interface and internal memory back to RESET_N
assertion default settings.
‘0’ = Normal Run/Idle State
‘1’ = Force a reset of registers to their default state
USB_ATTACH
USB Attach (and write protect)
‘0’ = SMBus slave interface is active
‘1’ = The hub will signal a USB attach event to an upstream device, and the
internal memory (address range 00h-FEh) is “write-protected” to prevent
unintentional data corruption.
2
8.2.2
I C EEPROM
The I2C EEPROM interface implements a subset of the I2C Master specification (Please refer to the
Philips Semiconductor Standard I2C-Bus specification for details on I2C bus protocols). The SMSC
hub’s I2C EEPROM interface is designed to attach to a single “dedicated” I2C EEPROM, and it
conforms to the Standard-mode I2C specification (100 kbit/s transfer rate and 7-bit addressing) for
protocol and electrical compatibility.
Note: Extensions to the I2C specification are not supported.
The hub acts as the master and generates the serial clock SCL, controls the bus access (determines
which device acts as the transmitter and which device acts as the receiver), and generates the START
and STOP conditions.
8.2.2.1
8.2.2.2
Implementation Characteristics
The hub will only access an EEPROM using the sequential read protocol.
Pull-Up Resistor
The circuit board designer is required to place external pull-up resistors (10 kΩ recommended) on the
SDA / SMBDATA & SCL / SMBCLK / CFG_SEL[0] lines (per SMBus 1.0 specification, and EEPROM
manufacturer guidelines) to VDD33 in order to assure proper operation.
2
8.2.2.3
I C EEPROM Slave Address
The slave address is 1010000.
Note: 10-bit addressing is NOT supported.
8.2.3
In-Circuit EEPROM Programming
The EEPROM can be programmed via ATE (automatic test equipment) by pulling RESET_N low
(which tri-states the hub’s EEPROM interface and allows an external source to program the EEPROM).
Revision 1.0 (3-11-09)
52
SMSC USB251x
DATASHEET
SMSC [ SMSC CORPORATION ]
