USB2642 datasheet(40/56 Pages) MICROCHIP

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USB2642

DS00001578C-page 40

 2014-2015 Microchip Technology Inc.

Assertion of RESET_N (external pin) causes the following:

All downstream ports are disabled, and PRTCTL power to downstream devices is removed.

The PHYs are disabled, and the differential pairs will be in a high-impedance state.

All transactions immediately terminate; no states are saved.

All internal registers return to the default state (in most cases, 00h).

The external crystal oscillator is halted.

The PLL is halted.

7.6.1.1

RESET_N for EEPROM Configuration

Note 7-1

All power supplies must have reached the operating levels mandated in Section 8.0, "DC

Parameters", prior to (or coincident with) the assertion of RESET_N.

7.6.2

USB BUS RESET

In response to the upstream port signaling a reset, the hub does the following:

FIGURE 7-1:

RESET_N TIMING FOR EEPROM MODE

TABLE 7-7:

RESET_N TIMING FOR EEPROM MODE

Name

Description

Min

Typ

Max

Units

RESET_N asserted

µsec

Device recovery/stabilization

500

µsec

8051 programs device configuration

msec

USB attach (see Note 7-1)

100

msec

Host acknowledges attach and signals USB reset

100

msec

USB idle

Undefined

msec

Completion time for requests (with or without data

stage)

msec

Note:

The hub does not propagate the upstream USB reset to downstream devices.

RESET_N

VSS

Hardware

reset

asserted

Device

Recovery/

Stabilization

8051 Sets

Configuration

Registers

Attach

USB

Upstream

USB Reset

recovery

Idle

Start

completion

request

response

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