USB2514 datasheet(44/63 Pages) MICROCHIP

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USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 2.2 (02-17-12)

SMSC USB251xB/xBi

DATASHEET

5.3.4

Stretching the SCLK Signal

The hub supports stretching of the SCLK by other devices on the SMBus. However, the hub does not

stretch the SCLK.

5.3.5

SMBus Timing

The SMBus slave interface complies with the SMBus Specification Revision 1.0 [3]. See Section 2.1,

AC Specifications

on page 3 for more information.

5.3.6

Bus Reset Sequence

The SMBus slave interface resets and returns to the idle state upon a START condition followed

immediately by a STOP condition.

5.3.7

SMBus Alert Response Address

The SMBALERT# signal is not supported by the hub.

5.4

Default Configuration

To put the SMSC hub in the default configuration, strap CFG_SEL[1:0] to 00b. This procedure

configures the hub to the internal defaults and enables the strapping options. To place the hub in

default configuration with overrides, see Table 5.1 on page 26 for the list of the options.

The internal default values are used for the registers that are not controlled by strapping option pins.

Refer to Section 5.1 on page 27 for the internal default values that are loaded when this option is

selected. For a list of strapping option pins, see Chapter 5 on page 26, and to configure the strapping

pins, see Section 3.3.1 on page 22.

5.5

Reset

The hub experiences the following two resets:

Hardware reset via the RESET_N pin

USB bus reset

5.5.1

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[x:1] to downstream devices is removed (unless

BC_EN[x:1] is enabled).

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.

The hub is operational 500

μs after RESET_N is negated. Once operational, the hub will do one of the

following, depending on configuration:

Read the strapping pins (default configuration with strapping options enabled)

Read configuration information from the external I2C EEPROM

Wait for configuration over SMBus.

USB2514 Datasheet(PDF) 44 Page - Microchip Technology

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