LPC47M14X datasheet(25/205 Pages) SMSC

25 / 205 page

SMSC DS – LPC47M14X

Page 25

Rev. 03/19/2001

ports. The internal 24MHz driven PLL (and the 48MHz in the Hub Block) will be started to complete the

Resume.

6.4.1

USB Downstream Port Selection

The LPC47M14x USB Hub has the ability to program, via BIOS, control register access or through external PIN

strapping options, the number of Down Stream Ports that are available to the User. There is also a “Pin Strapping”

option that will allow the board designer the ability to define the number of down stream ports that will be active via

during USB_PWR POR.

The LPC47M120 USB Hub block will make the following changes to its external signals and device class response

parameters:

1) All related input and output signals such as the associated Over-current sense pins (nUSBOC[x]) and Power

Enable (nPWREN[x]) pin are also disabled.

2) The USB Down Stream Port nUSBOC[x] input pin can be a NC (No Connect) pin or tied High (1). For EMI and

reduced Noise sensitivity, it is recommended that the pin be tied High (1).

3) The Power Enable (nPWREN[x]) pin will be forced low (0). For EMI and reduced Noise sensitivity, it is

recommended that the pin be tied High (1).

4) The associated PDx+ and PDx- pins will not be active can be a NC (No Connect) pin). For EMI and reduced

Noise sensitivity, it is recommended that the pin be tied High (1).

5) All Hub Device Class return descriptor must respond with the appropriate information relating to the number of

ports that are currently selected by the Strap Pins or control bits in the register described in Table 76 –

HubControl_1 Register Definition, shown on page 171, below, describes what fields now need to be

programmed bas on the number of enabled ports.

Table 2 – Hub Descriptor to be Modified

OFFSET

FIELD

PROGRAMMABLE

SIZE

DESCRIPTION

bDescLength

Number of bytes in this descriptor, including

this byte.

bDescriptorType

Descriptor Type

bNbrPorts

Number of downstream ports that this hub

supports. Selected by the “Strp0 and nStrp1”

input pins or the HubControl_1 register defined

Table 76

–

HubControl_1 Register

Definition, shown on page 171, below.

wHubCharacteristics

D1..D0: Power Switching Mode

00 - Ganged power switching (all ports’ power

at once)

01 - Individual port power switching

1X - No power switching (ports always powered

on when hub is on and off when hub is off).

D2:Identifies a Compound Device

0 - Hub is not part of a compound device

1 - Hub is part of a compound device

D4..D3: Over-current Protection Mode

00 - Global Over-current Protection. The hub

reports over-current as a summation of all

ports’ current draw, without a breakdown of

individual port over-current status.

01 - Individual Port Over-current protection.

The hub reports over-current on a per-port

basis. Each port has an over-current indicator.

1X -No Over-Current Protection. This option is

only allowed for bus-powered hubs that do not

implement over-current protection.

D15..D5: Reserved

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