LAN9500AI datasheet(35/213 Pages) MICROCHIP

35 / 213 page

 2010 - 2015 Microchip Technology Inc.

DS00001875A-page 35

LAN950x

5.3.1.6.8

Device Qualifier Descriptor

The fields in this descriptor are derived from Device Descriptor information that is stored in the EEPROM.

Note 5-14

Value is loaded from EEPROM, but must be equal to the Default Value in order to comply with the

USB 2.0 Specification and provide for normal device operation. Specification of any other value will

result in unwanted behavior and untoward operation.

5.3.1.6.9

String Descriptors

String Index = 0 (LANGID)

Note 1: If there is no valid/enabled EEPROM, or if all string lengths in the EEPROM are 0, then there are no strings,

so any host attempt to read the LANGID string will return stall in the Data Stage of the Control Transfer.

If there is a valid/enabled EEPROM, and if at least one of the string lengths in the EEPROM is not 0, then

the value contained at EEPROM addresses 0x0A-0x0B will be returned. These must be 0x0409 to allow for

proper device operation.

2: The device ignores the LANGID field in Control Read’s of Strings, and will not return the String (if it exists),

regardless of whether the requested LANGID is 0x0409 or not.

TABLE 5-11:

DEVICE QUALIFIER DESCRIPTOR

Offset

Field

Size

(Bytes)

Default

Value

Loaded

from

EEPROM

Description

00h

bLength

0Ah

Size of Descriptor in bytes (10 bytes)

01h

bDescriptorType

06h

Device Qualifier Descriptor (0x06)

02h

bcdUSB

0200h

Note 5-14

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

bMaxPacketSize0

40h

Note 5-14

Maximum Packet Size

08h

bNumConfigurations

01h

Note 5-14

Number of Other-Speed Configurations

09h

Reserved

00h

Must be zero

Note:

EEPROM values are from the Device Descriptor (including any EEPROM override) at the opposite HS/FS

operating speed. I.e., if the current operating speed is HS, then Device Qualifier data is based on the FS

Device Descriptor, and vice-versa.

TABLE 5-12:

LANGID STRING DESCRIPTOR

Offset

Field

Size

(Bytes)

Default

Value

Loaded

from

EEPROM

Description

00h

bLength

04h

Size of LANGID Descriptor in bytes (4

bytes)

01h

bDescriptorType

03h

String Descriptor (0x03)

02h

LANGID

None

Yes

Must be set to 0x0409 (US English).

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