USB2422 datasheet(23/47 Pages) MICROCHIP

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DS00001726B-page 23

USB2422

4.4.7

CONFIGURATION DATA BYTE 1 REGISTER (CFG1)

Address:

06h

Size:

8 bits

Bits

Description

Type

Default

Self or Bus Power (SELF_BUS_PWR)

Selects between Self- and Bus-Powered operation.

The Hub is either Self-Powered (draws less than 2mA of upstream bus

power) or Bus-Powered (limited to a 100mA maximum of upstream power

prior to being configured by the host controller).

When configured as a Bus-Powered device, the Hub consumes less than

100mA of current prior to being configured. After configuration, the Bus-

Powered Hub (along with all associated hub circuitry, any embedded devices

if part of a compound device, and 100mA per externally available

downstream port) must consume no more than 500mA of upstream VBUS

current. The current consumption is system dependent, and the OEM must

ensure that the USB2.0 specifications are not violated.

When configured as a Self-Powered device, <1mA of upstream VBUS

current is consumed and all ports are available, with each port being capable

of sourcing 500mA of current.

This field is set by the OEM using the SMBus interface option.

Please see the description under Dynamic Power for the self/bus power

functionality when dynamic power switching is enabled.

0 = Bus-Powered operation

1 = Self-Powered operation

Note:

If Dynamic Power Switching is enabled, this bit is ignored and the

LOCAL_PWR pin is used to determine if the hub is operating from

self or bus power.

R/W

RESERVED

High Speed Disable (HS_DISABLE)

Disables the capability to attach as either a High/Full- speed device, and

forces attachment as Full-speed only i.e. (no High-Speed support).

0 = High-/Full-Speed

1 = Full-Speed-Only (High-Speed disabled)

R/W

Multi-TT Enable (MTT_ENABLE)

Enables one transaction translator per port operation.

Selects between a mode where only one transaction translator is available

for all ports (Single-TT), or each port gets a dedicated transaction translator

(Multi-TT)

Note:

The host may force Single-TT mode only

0 = Single TT for all ports. Default to STT if MTT still exists

1 = One TT per port (multiple TT’s supported)

R/W

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