USB3503 datasheet(45/73 Pages) MICROCHIP

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DS00001584B-page 45

USB3503

7.4

Class-Specific Hub Descriptor

The following table provides class-specific Hub descriptor values.

Note:

The Hub must respond to Hub Class Descriptor type 29h (the USB 1.1 and USB 2.0 value) and 00h

(the USB 1.0 value).

TABLE 7-11:

CLASS-SPECIFIC HUB DESCRIPTOR

Offset

Field

Size

Value

Description

Length

09h

Size of this Descriptor.

DescriptorType

29h

Hub Descriptor Type.

NbrPorts

user

Number of downstream facing ports this Hub supports.

See Section 11.23.2.1 of the USB Specification for

additional details regarding the use of this field.

The value reported is implementation dependent, and is

derived from the value defined during Internal Default, or

serial port load. The PORT_DIS_SP field defines the

ports that are permanently disabled when in Self-

Powered operation, and the PORT_DIS_BP field defines

the ports that are permanently disabled when in Bus-

Powered operation.

Internal logic will subtract the number of ports which are

disabled, from the total number available (which is 3),

and will report the remainder as the number of ports

supported. The value reported to the host must coincide

with the current operating mode, and will be determined

by the following rules.

The field used to determine the value that is reported to

the host will be:

‘PORT_DIS_BP’ if SELF_BUS_PWR = ‘0’

‘PORT_DIS_SP’ if SELF_BUS_PWR = ‘1’

HubCharacteristics

user

Defines support for Logical power switching mode,

Compound Device support, Over-current protection, TT

Think Time, and Port Indicator support, See Section

11.23.2.1 in the USB Specification for additional details

regarding the use of this field.

The values delivered to a host are all derived from values

defined during Internal Default, or serial port load, and

are assigned as follows:

D1:0 = ‘00’b if PORT_PWR = ‘0’

D1:0 = ‘01’b if PORT_PWR = ‘1’

D2 = ‘COMPOUND’

D4:3 = ‘CURRENT_SNS’

D6:5 = ‘00’b for 8FS (max) bit times of TT think time.

D7 = hardcoded to ‘0’ (no Port Indicator Support)

D15:8 = ‘00000000’b

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