USB2640I Standard Microsystems Corp., USB2640I Datasheet - Page 26

• Manufacturer Part Number: USB2640I
• Description: Industrial Temperature Usb 2.0 Flash Media Controller And Usb Hub Combo
• Manufacturer: Standard Microsystems Corp.

Revision 2.0 (10-03-08)
6.4
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 I
The firmware looks for the signature ‘ATA2’ at the offset of 0xFC-0xFF in the I
reads in the I
EEPROM Data Descriptor on page 28
The SPI ROM required for the USB2640i/USB2641i must be 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 kΩ resistor. For 60 MHz operation, this pin must pulled up through a
100 kΩ resistor. SPI_SPD_SEL: This 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.
ROM BOOT Sequence
USB2640i/
USB2641i
2
USB2640i/
USB2641i
C ROM to configure the hardware and software internally. Please refer to section
Figure 6.4 USB2640i/USB2641i SPI ROM Connection
Figure 6.5 USB2640i/USB2641i I
SPI_CE_N
SPI_CLK / GPIO4 / SCL
SPI_DO / GPIO5 / SDA / SPI_SPD_SEL
SPI_DI
Industrial Temperature USB 2.0 Flash Media Controller and USB Hub Combo
DATASHEET
for the details of the configuration options.
26
3.3V
3.3V
10K
10K
2
C Connection
SCL
SDA
I
2
C ROM
CE#
CLK
DO
DI
DO
DI
SMSC USB2640i/USB2641i
2
SPI ROM
C ROM. The firmware
2
C ROM.
7.3.2