EZ-USB Datasheet, PDF (83/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

The Other Half of the I²C Story
The EZ-USB I²C controller serves two purposes. First, as described in this chapter, it
manages the serial EEPROM interface that operates automatically at power-on to deter-
mine the enumeration method. Second, once the 8051 is up and running, the 8051 can
access the I²C controller for general-purpose use. This makes a wide range of standard
I²C peripherals available to an EZ-USB system.
Other I²C devices can be attached to the SCL and SDA lines of the I²C bus as long as
there is no address conflict with the serial EEPROM described in this chapter. Chapter 4,
"EZ-USB Input/Output" describes the general-purpose nature of the I²C interface.
5.6 No Serial EEPROM
In the simplest case, no serial EEPROM is present on the I²C bus, or an EEPROM is
present but its first byte is not 0xB0 or 0xB2. In this case, descriptor data is supplied by a
table internal to the EZ-USB core. The EZ-USB chip comes on as the USB Default
Device, with the ID bytes shown in Table 5-6.
Table 5-6. EZ-USB Device Characteristics, No Serial EEPROM
Vendor ID
0x0547 (Cypress Semiconductor)
Product ID
0x2131 (EZ-USB)
Device Release 0xXXYY (depends on revision)
The USB host queries the device during enumeration, reads the device descriptor, and uses
the Table 5-6 bytes to determine which software driver to load into the operating system.
This is a major USB feature—drivers are dynamically matched with devices and automat-
ically loaded when a device is plugged in.
The no_EEPROM case is the simplest configuration, but also the most limiting. This
mode is used only for code development, utilizing Cypress software tools matched to the
ID values in Table 5-6.
Page 5-8
Chapter 5. EZ-USB CPU
EZ-USB TRM v1.9