USB2642 datasheet(19/56 Pages) MICROCHIP

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DS00001578C-page 19

USB2642

7.0

CONFIGURATION OPTIONS

7.1

Hub

Microchip’s USB2642 hub is fully compliant with the Universal Serial Bus 2.0 Specification (References). See

Chapter 11 (Hub Specification) 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, 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+ 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

Card Reader

The Microchip USB2642 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

- Supports storage addressability of up to 2TB

• MultiMediaCard 4.2

- 1/4/8 bit

- includes support for eMMC devices

7.3

I2C over USB Bridge

USB2642 offers a I2C over USB bridge functionality. Host initiated SCSI pass-through commands are sent to USB2642

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 assert GPO1 pin. This can be driving RST of the I2C slave device.

For additional configuration information and protocol details, see “USB2642 I2C Over USB Bridge User’s Guide”.

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