USB2517 datasheet(23/58 Pages) MICROCHIP

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 2013-2016 Microchip Technology Inc.

DS00001598B-page 23

USB2517/USB2517I

7.2.1.7

Bit

Number

Bit Name

Description

SELF_BUS_PWR

Self or Bus Power: 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 MCHP Hub consumes less

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

Powered MCHP 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 USB 2.0 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 either the SMBus or EEPROM interface

options.

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

tionality 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.

Reserved

HS_DISABLE

High Speed Disable: Disables the capability to attach as either a High/Full-

speed device, and forces attachment as Full-speed only (i.e. no Hi-Speed

support).

0 = High-/Full-Speed

1 = Full-Speed-Only (Hi-Speed disabled!)

MTT_ENABLE

Multi-TT 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

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

EOP_DISABLE

EOP Disable: Disables EOP generation of EOF1 when in Full-Speed mode.

During FS operation only, this permits the Hub to send EOP if no downstream

traffic is detected at EOF1. See Section 11.3.1 of the USB 2.0 Specification

for additional details. Note: generation of an EOP at the EOF1 point may pre-

vent a Host controller (operating in FS mode) from placing the USB bus in

suspend.

0 = EOP generation is normal

1 = EOP generation is disabled

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