USB4624 datasheet(42/58 Pages) MICROCHIP

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USB 2.0 HSIC Hi-Speed 4-Port Hub Controller

Datasheet

DS00001717A-page 42

 2014 Microchip Technology Inc.

8.4

Resets

The device has the following chip level reset sources:



Power-On Reset (POR)



External Chip Reset (RESET_N)



USB Bus Reset

8.4.1

Power-On Reset (POR)

A power-on reset occurs whenever power is initially supplied to the device, or if power is removed and

reapplied to the device. A timer within the device will assert the internal reset per the specifications

listed in Section 9.5.1, "Power-On Configuration Strap Valid Timing," on page 50.

8.4.2

External Chip Reset (RESET_N)

A valid hardware reset is defined as assertion of RESET_N, after all power supplies are within

operating range, per the specifications in Section 9.5.2, "Reset and Configuration Strap Timing," on

page 51. While reset is asserted, the device (and its associated external circuitry) enters Standby Mode

and consumes minimal current.

Assertion of RESET_N causes the following:

1. The PHY is disabled and the differential pairs will be in a high-impedance state.

2. All transactions immediately terminate; no states are saved.

3. All internal registers return to the default state.

4. The external crystal oscillator is halted.

5. The PLL is halted.

6. The HSIC Strobe and Data pins are driven low.

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.

8.4.3

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.

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