
RTL8305SB
2002/04/09
43
Rev.1.0
7.3.3 Example of Serial EEPROM: 24LC02
The 24LC02 interface is a 2-wire serial EEPROM interface providing 2K bits storage space. The 24LC02 should be 2.5V
compatible.
7.3.4 24LC02 Device Operation
Clock and Data transitions: The SDA pin is normally pulled high with an external resistor. Data on the SDA pin may change only
during SCL low time periods. Data changes during SCL high periods will indicate a start or stop condition as defined below.
Start condition
: A high-to-low transition of SDA with SCL high is a start condition which must precede any other command.
Stop condition:
A low-to-high transition of SDA with SCL high is a stop condition.
Acknowledge:
All addresses and data are transmitted serially to and from the EEPROM in 8-bit words. The 24LC02 sends a
zero to acknowledge that it has received each word. This happens during the ninth clock cycle.
Random Read
: A random read requires a "dummy" byte write sequence to load in the data word address.
Sequential Read
: For the RTL8305SB, the sequential reads are initiated by a random address read. After the 24LC02 receives
a data word, it responds with an acknowledgement. As long as the 24LC02 receives an acknowledgement, it will continue to
increment the data word address and clock out sequential data words in serial.
*
Start and Stop
Definition
SDA
SCL
START STOP
*
Output Acknowledge
SCL 1 8 9
DATA IN
DATA OUT
START ACKNOWLEDGE
*
Random Read
WORD DEVICE
ADDRESS ADDRESS n ADDRESS
SDA
DATA n
DUMMY WRITE
*
Sequential Read
DEVICE
ADDRESS
SDA
DATA n DATA n+1 … DATA n+x
A
DEVICE
S
W
R
S
S
R
A
A
A
N
R
A
A
S
N
A
R
A