LAN9500AI datasheet(32/213 Pages) MICROCHIP

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LAN950x

DS00001875A-page 32

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5.3.1.6.2

Configuration Descriptor

The Configuration Descriptor is initialized based on values stored in EEPROM. Table 5-5 shows the default Configura-

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

Note 5-5

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 5-6

The descriptor type for Configuration Descriptors specified in EEPROM is a “don’t care” and is always

overwritten by hardware as 0x02.

Note 5-7

Default value is 01h in Self Powered mode and FAh in Bus Powered mode.

5.3.1.6.3

Interface Descriptor 0 Default

Table 5-6 shows the default value for Interface Descriptor 0. This descriptor is initialized based on values stored in

EEPROM.

Note 5-8

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.

TABLE 5-5:

CONFIGURATION DESCRIPTOR

Offset

Field

Size

(Bytes)

Default

Value

Loaded

from

EEPROM

Description

00h

bLength

09h

Note 5-5

Size of the Configuration Descriptor in

bytes (9 bytes)

01h

bDescriptorType

02h

Note 5-6

Configuration Descriptor (0x02)

02h

wTotalLength

0027h

Note 5-5

Total length in bytes of data returned

(39 bytes)

04h

bNumInterfaces

01h

Note 5-5

Number of Interfaces

05h

bConfigurationValue

01h

Note 5-5

Value to use as an argument to select

this configuration

06h

iConfiguration

00h

Yes

Index of String Descriptor describing

this configuration

07h

bmAttributes

A0h

Yes

Bus powered and remote wakeup

enabled.

08h

bMaxPower

Note 5-7

Yes

Maximum Power Consumption is 500

mA.

Note:

The PWR_SEL and RMT_WKP straps affect the default value of bmAttributes.

TABLE 5-6:

INTERFACE DESCRIPTOR 0

Offset

Field

Size

(Bytes)

Default

Value

Loaded

From

EEPROM

Description

00h

bLength

09h

Note 5-8

Size of Descriptor in Bytes (9 Bytes

01h

bDescriptorType

04h

Note 5-8

Interface Descriptor (0x04)

02h

bInterfaceNumber

00h

Note 5-8

Number identifying this Interface

03h

bAlternateSetting

00h

Note 5-8

Value used to select alternative setting

04h

bNumEndpoints

03h

Note 5-8

Number of Endpoints used for this

interface (Less endpoint 0)

05h

bInterfaceClass

FFh

Yes

Class Code

06h

bInterfaceSubClass

00h

Yes

Subclass Code

07h

bInterfaceProtocol

FFh

Yes

Protocol Code

08h

iInterface

00h

Yes

Index of String Descriptor Describing

this interface

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