STW4810 datasheet(48/79 Pages) STMICROELECTRONICS

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STw4810

Functional description

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4.4.3

USB enable control

STw4810 OFF

In this state, the overall system is able to detect USB connection through IT_WAKE_UP ball

and with VBUS session valid comparator and ID detection ON.

IT_WAKE_UP is activated (low level) in either of the two following cases:

–

When Mini A connector cable is connected and ID goes low

–

When activity on VBUS, i.e. a mini B is connected and is able to communicate.

This mode is used to wake-up the modem platform. In this configuration, USBINTn

ball is not enabled.

STw4810 ON, USB driver not enabled

The USBINTn is now enabled.

If the USB cable is already connected while STw4810 is starting, the USB driver will be

enabled when power management is ready.

●

Wake-up USB driver conditions

–

A plug-in on a mini A-device and active ID detector

–

B device is connected and ready to start data transfer, VBUS is driven high

(session valid high)

–

Activity on USB registers (00h to 0Fh -

Table 9 to Table 16). Multimedia processor

ready to wake-up and set-up USB PHY.

–

Possibility to force PHY high (enable) when writing usb_en = 1 in USB EN register

(

Table 17)

●

Set condition: one among the following possibilities

–

External it_wake_up =0

–

usb_en = 1 by writing to I²C USB interface

–

Access to any other USB register (00h to 0Fh)

●

Power down USB driver conditions in order to set the USB driver to power down mode:

–

it_wake_up = 1, and only then

–

Set usb_en bit of USB EN register (

Table 17) to “0”

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