USB4604 datasheet(28/62 Pages) MICROCHIP

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USB 2.0 HSIC Hi-Speed 4-Port Hub Controller

Datasheet

DS00001716A-page 28

 2014 Microchip Technology Inc.

5.1

Boot Sequence

5.1.1

Standby Mode

If the external hardware reset is asserted, the hub will be in Standby Mode. This mode provides a very

low power state for maximum power efficiency when no signaling is required. This is the lowest power

state. In Standby Mode all internal regulators are powered off, the PLL is not running, and core logic

is powered down in order to minimize power consumption. Because core logic is powered off, no

configuration settings are retained in this mode and must be re-initialized after RESET_N is negated

high.

5.1.2

Hardware Initialization Stage (HW_INIT)

The first stage is the initialization stage and occurs on the negation of RESET_N. In this stage the

1.2V regulator is enabled and stabilizes, internal logic is reset, and the PLL locks if a valid REFCLK

is supplied. Configuration registers are initialized to their default state and strap input values are

latched. The device will complete initialization and automatically enter the next stage. Because the

digital logic within the device is not yet stable, no communication with the device using the SMBus is

possible. Configuration registers are initialized to their default state.

If there is a REFCLK present, the next state is SW_INIT.

5.1.3

Software Initialization Stage (SW_INIT)

Once the hardware is initialized, the firmware can begin to execute. The internal firmware checks for

an external SPI ROM. The firmware looks for an external SPI flash device that contains a valid

signature of “2DFU” (device firmware upgrade) beginning at address 0xFFFA. If a valid signature is

found, then the external ROM is enabled and the code execution begins at address 0x0000 in the

external SPI device. If a valid signature is not found, then execution continues from internal ROM. SPI

ROMs used with the device must be 1 Mbit and support either 30 MHz or 60 MHz. The frequency

used is set using the SPI_SPD_SEL configuration strap. Both 1- and 2-bit SPI operation is supported.

For optimum throughput, a 2-bit SPI ROM is recommended. Both mode 0 and mode 3 SPI ROMS are

also supported. Refer to Section 6.3.2, "SPI Speed Select (SPI_SPD_SEL)," on page 33 for additional

information on selection of the SPI speed.For all other configurations, the firmware checks for the

presence of an external I2C/SMBus. It does this by asserting two pull down resistors on the data and

clock lines of the bus. The pull downs are typically 50Kohm. If there are 10Kohm pull-ups present, the

device becomes aware of the presence of an external SMBus/I2C bus. If a bus is detected, the

firmware transitions to the SOC_CFG state.

5.1.4

SOC Configuration Stage (SOC_CFG)

In this stage, the SOC may modify any of the default configuration settings specified in the integrated

ROM such as USB device descriptors, or port electrical settings, and control features such as

upstream battery charging detection.

There is no time limit. In this stage the firmware will wait indefinitely for the SMBus/I2C configuration.

When the SOC has completed configuring the device, it must write to register 0xFF to end the

configuration.

5.1.5

Configuration Stage (CONFIG)

Once the SOC has indicated that it is done with configuration, then all the configuration data is

combined. The default data, the SOC configuration data, the OTP data are all combined in the firmware

and device is programmed.

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