EZ-USB Datasheet, PDF (74/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

Table 4-2. Strap Boot EEPROM Address Lines to These Values
Bytes
Example
EEPROM
A2
A1
A0
16 24LC00* N/A
N/A
N/A
128 24LC01
0
0
0
256 24LC02
0
0
0
4K 24LC32
0
0
1
8K 24LC64
0
0
1
* This EEPROM does not have address pins
The I²C controller performs a three-step test at power-on to determine whether a one-byte-
address or a two-byte-address EEPROM is attached. This test proceeds as follows:
1. The I²C controller sends out a “read current address” command to I²C sub-address
000 (10100001). If no ACK is returned, the controller proceeds to step 2. If ACK
is returned, the one-byte-address device is indicated. The controller discards the
data and proceeds to step 3.
2. The I²C controller sends out a “read current address” command to I²C sub-address
001 (10100011). If ACK is returned, the two-byte-address device is indicated.
The controller discards the data and proceeds to step 3. If no ACK is returned, the
controller assumes that a valid EEPROM is not connected, assumes the “No Serial
EEPROM” mode, and terminates the boot load.
3. The I²C controller resets the EEPROM address pointer to zero (using the appropri-
ate number of address bytes), then reads the first EEPROM byte. If it does not
read 0xB0 or 0xB2, the controller assumes the “No Serial EEPROM” mode. If it
reads either 0xB0 or 0xB2, the controller copies the next six bytes into internal
storage, and if it reads 0xB2, it proceeds to load the EEPROM contents into inter-
nal RAM.
EZ-USB TRM v1.9
Chapter 4. EZ-USB CPU
Page 4-13