at43usb355 ATMEL Corporation, at43usb355 Datasheet - Page 98

• Manufacturer Part Number: at43usb355
• Description: At43usb355 Full-speed Usb Microcontroller With Embedded Hub, Adc And Pwm
• Manufacturer: ATMEL Corporation

Hub and Port Power
Management
Overcurrent Sensing
Port Power Switching
98
AT43USB355
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).
Overcurrent protection and power switching are required for the external downstream ports
only. In the AT43USB355, these tasks are completely programmable. This means that any
type of hub is achievable with the AT43USB355: self-powered or bus-powered hubs, per port
or global overcurrent protection, individual or ganged port power switching.
The use of the MCU's GPIO pins are required to interface to the external power supply moni-
toring and switching. The on-chip hardware of the AT43USB355 contains the circuitry to
handle all the possible combinations of port power management tasks. The firmware defines
the exact configuration.
The AT43USB355 is capable of detecting overcurrent during active operation only, or during
any condition even when the hub is in the suspended state. When overcurrent in the active
state only is desired, any GPIO pin of the AT43USB355 can be used to sense and the over-
current condition. Control of the condition must be performed by the firmware. If overcurrent
detection under any condition is desired, then specific GPIO pins must be used to sense the
overcurrent and the proper bit(s) of UOVCER set. In Global Overcurrent Protection mode,
overcurrent sensing must be routed to GPIO PD0. In Individual Port Overcurrent Protection
mode Port2 and Port 3 overcurrent sensing must be assigned to GPIO PD0 and PD1. In the
following description, it is assumed that overcurrent protection is required under any condition.
1. Global Overcurrent Protection – In this mode, the Port Overcurrent Indicator and
2. Individual Port Overcurrent Protection – The Hub Overcurrent Indicator and Hub
1. Gang Power Switching – One of the microcontroller GPIO pins, PWRN, must be pro-
Port Overcurrent Indicator Change should be set to 0's. For the AT43USB355 an exter-
nal solid state switch, such as the Micrel MIC2025-2, 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 all
external downstream ports. The hub status change is reported on the next IN token
through the hub's interrupt endpoint, Endpoint1.
Overcurrent Indicator Change bits should be set to 0's. One MIC2026-2 is required for
the two USB ports. The FLG output of the MIC2026-2 associated with Port2 should be
connected to GPIO PD0 and the other FLG output to PD1. 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 AT43USB355 reports the port status change through
the hub's Endpoint1.
grammed as an output to control the external switch such as the MIC2025-2. 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.
2603G–USB–04/06