USB3813 datasheet(41/57 Pages) MICROCHIP

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USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications

Datasheet

 2014 Microchip Technology Inc.

DS00001715A-page 41

Note: All power supplies must have reached the operating levels mandated in Section 9.2, "Operating

Conditions**," on page 45, prior to (or coincident with) the assertion of RESET_N.

8.3.3

USB Bus Reset

In response to the upstream port signaling a reset to the device, the device performs the following:

Note: The device does not propagate the upstream USB reset to downstream devices.

1. Sets default address to 0.

2. Sets configuration to: Unconfigured.

3. Moves device from suspended to active (if suspended).

4. Complies with Section 11.10 of the USB 2.0 Specification for behavior after completion of the

reset sequence.

The host then configures the device in accordance with the USB Specification.

8.4

Reference Clock

The device’s reference clock (REFCLK) input can be driven with a square wave from 0V to VDD33

and is compatible with several different reference frequencies as shown in Table 8.4. The REFSEL[1:0]

inputs must be configured to select the default input reference clock frequency that matches the clock

frequency applied to REFCLK. The REFSEL[1:0] inputs are latched upon entering the HUB.config

stage and are ignored afterward. REFSEL[1:0] settings are provided in Table 8.4.

Note: The frequencies shown for each REFSEL[1:0] combination in Table 8.4 are the default values.

The frequencies associated with each specific REFSEL[1:0] value can be customized to

support other frequencies. Refer to the Pro-Touch Configuration Tool documentation for

additional information.

Table 8.4 Default Reference Clock Frequencies

REFSEL[1:0]

FREQUENCY (MHz)

‘00’

38.4

‘01’

26.0

‘10’

19.2

‘11’

12.0

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