2-Port USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 1.3 (12-27-11)

14

SMSC USB2412

DATASHEET

Chapter 3 Internal Default Configuration

SMSC’s USB 2.0 hub is fully compliant with the USB Specification1.. Refer to Chapter 10 (Hub

Specification) for general details regarding hub operation and functionality.

The hub provides one Transaction Translator (TT) that is shared by both downstream ports (defined

as Single-TT configuration). The TT contains 4 non-periodic buffers.

3.1

Hub Configuration

The USB2412 only supports internal defaults with the exception of the non-removable strap option

(using NON_REM[1:0]). The hub internal default settings are as follows:

Internal Default Configuration without over-rides

Strap options enabled

Self-powered operation enabled

Individual power switching

Individual over-current sensing

3.2

Reset

There are two different resets that the hub experiences. One is a hardware reset via RESET_N and

the second is a USB Bus Reset.

3.2.1

External Hardware RESET_N

A valid hardware reset is defined as assertion of RESET_N for a minimum of 1

μs 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.

Assertion of RESET_N 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, 00h).

5. The external crystal oscillator is halted.

6. The PLL is halted.

7. The hub is “operational” 500

μs after RESET_N is negated.