TUSB8042AI datasheet(22/64 Pages) TI2

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7.4 Device Functional Modes

7.4.1 External Configuration Interface

The TUSB8042A supports a serial interface for configuration register access. The device can be configured by

an attached I2C EEPROM or accessed as a target by an external SMBus controller. The external interface is

enabled when both the SCL/SMBCLK and SDA/SMBDAT pins are pulled up to 3.3V at the deassertion of reset.

The mode, I2C controller or SMBus target, is determined by the state of SMBUSz/SS_SUSPEND pin at reset.

7.4.2 I2C EEPROM Operation

The TUSB8042A supports a single-controller, standard mode (100KHz) or fast mode (400KHz) connection

to a dedicated I2C EEPROM when the I2C interface mode is enabled. In I2C mode, the TUSB8042A reads

the contents of the EEPROM at bus address 1010000b using 7-bit addressing starting at address 0. The

TUSB8042A reads the entire EEPROM contents using a single burst read transaction. The burst read

transaction ends when the address reaches FFh .

If the value of the EEPROM contents at address byte 00h equals 55h, the TUSB8042A loads the configuration

registers according to the EEPROM map. If the first byte is not 55h, the TUSB8042A exits the I2C mode

and continues execution with the default values in the configuration registers. The hub is not connect on the

upstream port until the configuration is completed.

Note

The bytes located above offset Ah are optional. The requirement for data in those addresses

is dependent on the options configured in the Device Configuration, and Device Configuration 2

registers.

The minimum size I2C EEPROM required is 2Kbit.

For details on I2C operation refer to the UM10204 I2C-bus Specification and User Manual.

7.4.3 Port Configuration

The TUSB8042A port configurations can be selected by registers or efuse. The Port Used Configuration register

(USED[3:0]) define how many ports can possibly be reported by the hub. The device removable configuration

or not. The USB 2.0 Only Port register (USB2_ONLY[3:0]) define whether or not a used port is reported as part

of the USB 2.0 hub or both the USB2.0 and SS hubs. The USB2_ONLY field enables the USB2.0 port even if the

corresponding USED bit is low. Table 7-4 shows examples of the possible combinations.

TUSB8042A

SLLSF93A – JUNE 2019 – REVISED JANUARY 2025

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TUSB8042AI Datenblatt(PDF) 22 Page - Texas Instruments