USB2502

DS000002248A-page 14

 2007 - 2016 Microchip Technology Inc.

5.1.1.16

Self-powered Hub Controller Current

When in Self-Powered configuration, Maximum current requirements of the Hub Controller in 2mA increments.

This field is set by the OEM using either the SMBus or EEPROM interface options.

5.1.1.17

Bus-Powered Hub Controller Current

When in Bus-Powered configuration, Maximum current requirements of the Hub Controller in 2mA increments.

This field is set by the OEM using either the SMBus or EEPROM interface options.

5.1.1.18

Power-On Timer

Time (in 2ms intervals) from the time power-on sequence begins on a port until power is good on that port. System soft-

ware uses this value to determine how long to wait before accessing a powered-on port.

This field is set by the OEM using either the SMBus or EEPROM interface options.

5.1.1.19

Power Switching Polarity

The selection of active state “polarity” for the PRTPWR2 pin is made by a strapping option only.

5.1.2

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+ or 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+ or D- pull-up resistor within 10

seconds.

5.2

EEPROM Interface

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 Table 5-1 User-Defined Descriptor Data for a list of data fields available.

5.2.1

fer rate and 7-bit addressing) for protocol and electrical compatibility.

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.

5.2.1.1

Implementation Characteristics

Please refer to the MicroChip 24AA00 DataSheet for Protocol and Programming specifics.

5.2.1.2

Pull-Up Resistor

The Circuit board designer is required to place external pull-up resistors (10K

 recommended) on the SDA/SMBDATA

& SCL/SMBCLK/CFG_SELO lines (per SMBus 1.0 Specification, and EEPROM manufacturer guidelines) to Vcc in

order to assure proper operation.

5.2.1.3

Slave address is 1010000.

Note:

Note:

10-bit addressing is NOT supported.