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USB System Architecture (USB 2.0).pdf
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Chapter 19: USB Device Configuration

Table 19-9: Configuration Descriptor Definition

Offset

Field Name

Size

Value

Description

 

 

(bytes)

 

 

 

 

 

 

 

 

 

 

 

 

8

MaxPower

1

X2 ma

Maximum power consumption of USB

 

 

 

 

device from the bus in this specific configu-

 

 

 

 

ration when the device is fully operational.

 

 

 

 

Expressed in 2 ma units (i.e., 50 = 100 ma).

 

 

 

 

 

Other Speed Configuration Descriptor

The other speed configuration descriptor provides information regarding the configuration of a high-speed capable device if it were operating at the other speed. The format of this configuration descriptor is identical to the standard configuration descriptor as shown in Table 19-10.

Table 19-10: Other Speed Configuration Descriptor

Offset

Field Name

Size

Value

Description

 

 

 

 

 

 

 

 

 

 

0

Desc. Size

1

Number

size of descriptor

 

 

 

 

 

1

Desc. Type

1

Constant

other speed configuration type

 

 

 

 

 

2

Total Length

2

Number

total length of data returned

 

 

 

 

 

4

Number of Inter-

1

Number

number of interfaces supported by

 

faces

 

 

this speed configuration

 

 

 

 

 

5

Configuration

1

Number

value used to select configuration

 

Value

 

 

 

 

 

 

 

 

6

Config. String

1

Index

index of string descriptor

 

Index

 

 

 

 

 

 

 

 

7

Attributes

1

Bitmap

same as configuration descriptor

 

 

 

 

 

8

Max Power

1

X2 ma

same as configuration descriptor

 

 

 

 

 

363

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