USB82642 datasheet(19/64 Pages) MICROCHIP

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DS60001253F-page 19

USB82642

7.0

CONFIGURATION OPTIONS

7.1

Hub

Microchip’s USB 2.0 hub is fully compliant to the Universal Serial Bus 2.0 Specification [3]. See Chapter 11 (Hub Spec-

ification) for general details regarding hub operation and functionality.

The hub provides a single Transaction Translator (TT) shared by both downstream ports. The TT contains 4 non-peri-

odic buffers.

7.1.1

HUB CONFIGURATION OPTIONS

The Microchip hub supports a large number of configurable features (some are mutually exclusive). There are two prin-

cipal ways to configure the hub:

• default settings

• settings loaded from an external EEPROM or SPI Flash device

7.1.1.1

Power Switching Polarity

The hub will only support active high power controllers.

7.1.2

VBus DETECT

According to Section 7.2.1 of the USB 2.0 Specification [3], 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 sec-

onds.

7.2

Card Reader

The Microchip USB82642 is fully compliant with the following flash media card reader specifications:

• Secure Digital 2.0

- SDSC, SDHC, and SDXC

- mircoSD and reduced form factor media

- SDIO - using the SDIO over USB bridge

• MultiMediaCard 4.2

- 1/4/8 bit

- includes support for eMMC devices

7.3

I2C over USB Bridge

USB82642 offers a I2C over USB bridge functionality. Host initiated SCSI pass-through commands are sent to

USB82642 using Mass Storage Class driver to control I2C master interface. Additional support for detecting clock

stretching during reads is also provided.

The following features are exposed through host side I2C API:

• Write_I2C_Stream

- Send any length of data over the I2C interface.

- The sequence follows the I2C protocol for writing data.

• WriteRead_I2C_Stream

- Read any length of data over the I2C interface.

- The sequence follows the I2C protocol for reading data.

• GPIO_1_SET_OUTPUT

- This method allows an application to control GPO1 pin. This can be driving RST of the I2C slave device.

For additional configuration information and protocol details, see the USB to I2C Bridge Reference Guide [1].

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