LAN9730 datasheet(35/222 Pages) MICROCHIP

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 2012-2015 Microchip Technology Inc.

DS00001946A-page 35

LAN9730/LAN9730i

4.3.1.5

USB Command Processing

The UDC is programmed to decode USB commands. After a standard command is decoded by the UDC, it may be

passed to the CTL for completion. The CTL is responsible for implementing the Get Descriptor and vendor commands.

In order to implement the Get Descriptor command for String Descriptors, the CTL manages a 128 x 32 register file

which stores the string values for Language ID, Manufacturer ID, Product ID, Serial Number, Configuration, and Inter-

face. The RAM’s contents is initialized via the EEPROM, after a system reset occurs.

When the UDC decodes a Get Descriptor command, it will pass a pointer to the CTL. The CTL uses this pointer to deter-

mine what the command is and how to fill it.

4.3.1.6

USB Descriptors

The following subsections describe the USB descriptors.

4.3.1.6.1

Device Descriptor

The Device Descriptors are initialized based on values stored in EEPROM. Table 4-4 shows the default Device Descrip-

tor values.

Note 4-1

The descriptor length and descriptor type for Device Descriptors specified in EEPROM are “don’t

cares” and are always overwritten by hardware as 0x12 and 0x01, respectively.

TABLE 4-3:

STRING DESCRIPTOR INDEX MAPPINGS

Index

String Name

Language ID

Manufacturer ID

Product ID

Serial Number

Configuration String

Interface String

TABLE 4-4:

DEVICE DESCRIPTOR

Offset

Field

Size

(Bytes)

Default Value

Loaded from

EEPROM

Description

00h

bLength

12h

Note 4-1

Size of the descriptor in bytes

(18 bytes)

01h

bDescriptorType

01h

Note 4-1

Device descriptor (0x01)

02h

bcdUSB

0200h

Note 4-2

USB Specification Number which

device complies to.

04h

bDeviceClass

FFh

Yes

Class Code

05h

bDeviceSubClass

00h

Yes

Subclass Code

06h

bDeviceProtocol

FFh

Yes

Protocol Code

07h

bMaxPacketSize

40h

Note 4-2

Maximum Packet Size for Endpoint 0

08h

IdVendor

0424h

Yes

Vendor ID

0Ah

IdProduct

9730h

Yes

Product ID

0Ch

bcdDevice

Note 4-3

Yes

Device Release Number

0Eh

iManufacturer

00h

Yes

Index of Manufacturer String Descriptor

0Fh

iProduct

00h

Yes

Index of Product String Descriptor

10h

iSerialNumber

00h

Yes

Index of Serial Number String Descrip-

tor

11h

bNumConfigurations

01h

Note 4-2

Number of possible configurations

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