USB82642 datasheet(20/64 Pages) MICROCHIP

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USB82642

DS60001253F-page 20

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7.4

SDIO Over USB Bridge

The SDIO over USB bridge allows for transmission of multiple types of data from an SDIO device over USB. The SDIO

over USB bridge uses USB Mass Storage Class Bulk-Only Transport and SCSI pass through to support this feature.

The USB82642 utilizes the following specifications:

• USB Mass Storage Class Specification Overview [4]

• USB Mass Storage Class Bulk-Only Transport [5]

• SCSI Architecture Model - 2 (SAM-2) [6]

• SCSI Primary Commands - 2 (SPC-2) [6]

• SD Specifications Part 1 Physical Layer Specification [7]

• SD Specifications Part E1 SDIO Specification [8]

• SD Specifications Part A2 SD Host Controller Standard Specification [9]

7.4.1

PROTOCOL OVERVIEW

For additional protocol information see the SDIO over USB Bridge Reference Guide [2].

7.4.1.1

USB Enumeration

A compliant device will enumerate at least one Interface Descriptor with the USB BaseClass of Mass Storage Device

Class

, SubClass of SCSI transparent command set, and Protocol of Bulk-Only Transport. See USB Mass Storage Class

Specification Overview [4] Tables 2.1 and 3.1.

7.4.1.2

USB Bulk-Only Transport

The protocol will be encapsulated by Command Block Wrappers (CBWs), where the CBWCB field depicted in Table 5.1

of the USB Mass Storage Class Bulk-Only Transport [5] document, Section 5, contains the SCSI Command Descriptor

Blocks (CDBs). Data is returned according to the specific definition of each CDB.

The execution status of each CDB will be returned in a Command Status Wrapper (CSW) as defined Section 5.2 of the

same document.

7.5

System Configurations

7.5.1

EEPROM/SPI INTERFACE

The USB82642 can be configured via a 2-wire (I2C) EEPROM (512x8) or an external SPI flash device containing the

firmware for the USB82642. If an external configuration device does not exist, the internal default values will be used.

If one of the external devices is used for configuration, the OEM can update the values through the USB interface. The

hub will then attach to the upstream USB host.

The USBDM tool set is available in the Hub Card reader combo software release package.

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