LAN9500AI datasheet(31/213 Pages) MICROCHIP

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DS00001875A-page 31

LAN950x

5.3.1.6

USB Descriptors

The following subsections describe the USB descriptors.

5.3.1.6.1

Device Descriptor

The Device Descriptors are initialized based on values stored in EEPROM. Table 5-4 shows the default Device Descrip-

tor values. These values are used for both Full-Speed and Hi-Speed operation.

Note 5-1

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.

Note 5-2

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.

Note 5-3

Product IDs are:

Note 5-4

Default value is dependent on device release. MSB matches the device release and LSB hardcoded

to 00h. The initial release value is 01h.

TABLE 5-4:

DEVICE DESCRIPTOR

Offset

Field

Size

(Bytes)

Default

Value

Loaded

from

EEPROM

Description

00h

bLength

12h

Note 5-1

Size of the Descriptor in Bytes (18

bytes)

01h

bDescriptorType

01h

Note 5-1

Device Descriptor (0x01)

02h

bcdUSB

0200h

Note 5-2

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 5-2

Maximum Packet Size for Endpoint 0

08h

IdVendor

0424h

Yes

Vendor ID

0Ah

IdProduct

Note 5-3

Yes

Product ID

0Ch

bcdDevice

Note 5-4

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

Descriptor

11h

bNumConfigurations

01h

Note 5-2

Number of Possible Configurations

Product

LAN9500/LAN9500i

9500h

LAN9500A/LAN9500Ai

9E00h

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