USB2502-HT datasheet(33/44 Pages) SMSC

33 / 44 page

2-Port USB 2.0 Hub Controller

Datasheet

SMSC USB2502

Revision 2.1 (12-06-06)

DATASHEET

5.6.1

External Hardware RESET_N

A valid hardware reset is defined as, assertion of RESET_N for a minimum of 1us after all power

supplies are within operating range. While reset is asserted, the Hub (and its associated external

circuitry) consumes less than 500

μA of current from the upstream USB power source (300μA for the

Hub and 200

μA for the external circuitry).

Assertion of RESET_N (external pin) causes the following:

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

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

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

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

5. The external crystal oscillator is halted.

6. The PLL is halted.

7. LED indicators are disabled.

The Hub is “operational” 500

μs after RESET_N is negated.

Once operational, the Hub immediately reads OEM-specific data from the external EEPROM (if the

SMBus option is not disabled).

5.6.1.1

RESET_N for Strapping Option Configuration

Figure 5.2 Reset_N Timing for Default/Strap Option Mode

Table 5.5 Reset_N Timing for Default/Strap Option Mode

NAME

DESCRIPTION

MIN

TYP

MAX

UNITS

RESET_N Asserted.

μsec

Strap Setup Time

16.7

nsec

Strap Hold Time.

16.7

1400

nsec

hub outputs driven to inactive logic states

2.0

1.5

μsec

USB Attach (See Note).

100

msec

Valid

Don’t Care

Driven by Hub if strap is an output.

RESET_N

VSS

Strap Pins

VSS

Hardware

reset

asserted

Read Strap

Options

Drive Strap

Outputs to

inactive

levels

Attach

USB

Upstream

USB Reset

recovery

Idle

Start

completion

request

response

USB2502-HT 数据表(PDF) 33 Page - SMSC Corporation

USB2502-HT 数据表(HTML) 33 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

数据表下载