
EZ-USB FX2 Technical Reference Manual
Page 3-4 EZ-USB FX2 Technical Reference Manual v2.1
3.4 EEPROM Boot-load Data Formats
This section describes three EEPROM boot-load scenarios and the EEPROM data formats that
support them. The three scenarios are:
• No EEPROM, or EEPROM with invalid boot data
• “C0” EEPROM (load custom VID / PID / DID only)
• “C2” EEPROM (load firmware to on-chip RAM)
3.4.1 No EEPROM or Invalid EEPROM
In the simplest scenario, either no serial EEPROM is present on the I²C-compatible bus or an
EEPROM is present, but its first byte is neither 0xC0 nor 0xC2. In this case, descriptor data is sup-
plied by hardwired internal FX2 tables. The FX2 enumerates as the
Default USB Device
, with the
ID bytes shown in Table 3-3.
Pull-up resistors are required on the SCL/SDA pins even if no device is connected. The resistors
are required to allow FX2 logic to detect the “No EEPROM / Invalid EEPROM” condition.
The USB host queries the FX2 Default USB Device during enumeration, reads its device descrip-
tor, and uses the IDs in Table 3-3 to determine which software driver to load into the operating sys-
tem. This is a major USB feature — drivers are dynamically matched with devices and
automatically loaded when a device is plugged in.
The “No EEPROM / Invalid EEPROM” scenario is the simplest configuration, and also the most
limiting. This configuration must only be used for code development, utilizing Cypress software
tools matched to the ID values in Table 3-3; no USB peripheral based on the FX2 may use this
configuration.
Table 3-3. FX2 Device Characteristics, No EEPROM / Invalid EEPROM
Vendor ID
0x04B4 (Cypress Semiconductor/)
Product ID
0x8613 (EZ-USB FX2)
Device Release
0xXXYY (depends on revision)
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