USB4640 datasheet(24/64 Pages) SMSC

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High Speed Inter-Chip (HSIC) USB 2.0 Hub and Flash Media Controller

Datasheet

Revision 1.0 (06-09-09)

SMSC USB4640/USB4640i

DATASHEET

6.4

ROM BOOT Sequence

After power-on reset, the internal firmware checks 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 code execution begins at address 0x0000 in the external

SPI device. Otherwise, code execution continues from the internal ROM.

If there is no SPI ROM detected, the internal firmware then checks for the presence of an I2C ROM.

The firmware looks for the signature ‘ATA2’ at the offset of FCh-FFh and ‘ecf1’ at the offset of 17Ch-

17Fh in the I2C ROM. The firmware reads in the I2C ROM to configure the hardware and software

internally. Please refer to Section 8.3.2, "EEPROM Data Descriptor," on page 29 for the details of the

configuration options.

The SPI ROM required for the USB4640/USB4640i is a recommended minimum of 1 Mbit and support

either 30 MHz or 60 MHz. The frequency used is set using the SPI_SPD_SEL. For 30 MHz operation,

this pin must be pulled to ground through a 100 k

Ω resistor. For 60 MHz operation, this pin must pulled

up through a 100 k

Ω resistor.

The SPI_SPD_SEL pin is used to choose the speed of the SPI interface. During nRESET assertion,

this pin will be tri-stated with the weak pull-down resistor enabled. When nRESET is negated, the value

on the pin will be internally latched, and the pin will revert to SPI_DO functionality. The internal pull-

down will be disabled.

The firmware can determine the speed of operation on the SPI port by checking the SPI_SPEED in

the SPI_CTL register (0x2400 - RESET = 0x02). 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.

Figure 6.4 SPI ROM Connection

Figure 6.5 I2C Connection

SPI ROM

SPI_CE_n

SPI_CLK / GPIO4 / SCL

SPI_DI

SPI_DO / GPIO5 / SDA / SPI_SPD_SEL

CE#

CLK

USB4640/40i

I2C ROM

SCL

SDA

3. 3 V

10 K

USB4640/40i

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