AT43USB326 datasheet(71/102 Pages) ATMEL

71 / 102 page

AT43USB326

3313D–USB–04/06

Set by hardware due to babble, physical disconnect or overcurrent except for Port 1 in which

case it is set by hardware at EOF2 due to hardware events. Cleared by firmware via Host

request ClearPortFeature(PORT_ENABLE).

• Bit 0 – PCSC: Port Connect Status Change

0 = No change has occurred on Current Connect Status

1 = Current Connect Status has changed

This bit is set by hardware at EOF2 after it detects a connect or disconnect at a port, except for

Port 1. Hardware sets this bit for Port 5 after a hub reset. Cleared by firmware via Host request

ClearPortFeature(PORT_CONNECTION).

Hub and Port Power

Management

The embedded hub in a keyboard will most likely be a bus-powered hub even though the hard-

ware of the AT43USB326 is designed to accommodate both types of hubs. Management of

the downstream port power is also defined by the firmware: per port or global overcurrent

sensing, individual or gang power switching. While the interface to the external power supply

monitoring and switching is achieved through the microcontroller’s GPIO pins, the USB hard-

ware of the AT43USB326 contains the circuitry to handle all the possible combinations port

power management tasks.

Overcurrent Sensing

If programmed for global overcurrent protection, the AT43USB326 is capable of detecting an

overcurrent in its downstream port even while it is in the suspend state. This mode is enabled

through the Overcurrent Detect Register, UOVCER, which controls the PD0 pin used for over-

current input sensing.

Global Overcurrent Protection – In this mode, the Port Overcurrent Indicator and

Port Overcurrent Indicator Change should be set to 0's. For the AT43USB326 an exter-

nal solid state switch, such as the Micrel MIC2545-2, is required to switch power to the

external USB ports. The FLG# output of the switch should be connected to PD0. When

an overcurrent occurs, FLG# is asserted and the firmware should set the Hub Overcur-

rent Indicator and Hub Overcurrent Indicator Change and switch off power to the hub.

Individual Port Over-current Protection – The Hub Overcurrent Indicator and Hub

Overcurrent Indicator Change bits should be set to 0's. One MIC2026-2 is required for

the two USB ports. Each of the FLG# outputs of the MIC2026-2 should be connected

to an unused microcontroller port. An overcurrent is indicated by assertion of FLG#.

The firmware sets the corresponding port's Overcurrent Indicator and the Overcurrent

Indicator Change bits and switches off power to the port. At the next IN token from the

Host, the AT43USB326 reports the status change.

Port Power Switching

Gang Power Switching – One of the microcontroller I/O port pins must be pro-

grammed as an output to control the external switch, PWRN. Switch ON is requested

by the USB Host through the SetPortFeature(PORT_POWER) request. Switch OFF is

executed upon receipt of a ClearPortFeature(PORT_POWER) or upon detecting an

overcurrent condition. The firmware clears the Power Control Bit. Only if all of the

Power Control Bits of ports 2 and 3 are cleared should the firmware de-assert the

PWRN pin.

Individual Power Switching – One microcontroller I/O port pin must be assigned for

each USB port to control the external switch, PWRxN, where x = 2, 3. Each of the

Power Control Bits controls one PWRxN.

Multiple Ganged Overcurrent Protection – Overcurrent sensing is grouped physi-

cally into one or more gangs, but reported individually.

AT43USB326 Arkusz danych(PDF) 71 Page - ATMEL Corporation

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