AT24C02B Datasheet, PDF (6/26 Pages) ATMEL Corporation – Two-wire Serial EEPROM

3. Device Operation
CLOCK and DATA TRANSITIONS: The SDA pin is normally pulled high with an external device.
Data on the SDA pin may change only during SCL low time periods (see Figure 5-2 on page 8).
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 (see Figure 5-3 on page 8).
STOP CONDITION: A low-to-high transition of SDA with SCL high is a stop condition. After a
read sequence, the stop command will place the EEPROM in a standby power mode (see Fig-
ure 5-3 on page 8).
ACKNOWLEDGE: All addresses and data words are serially transmitted to and from the
EEPROM in 8-bit words. The EEPROM sends a zero to acknowledge that it has received each
word. This happens during the ninth clock cycle.
STANDBY MODE: The AT24C02B features a low-power standby mode which is enabled: (a)
upon power-up and (b) after the receipt of the STOP bit and the completion of any internal
operations.
2-Wire Software Reset: After an interruption in protocol, power loss or system reset, any 2-wire
part can be reset by following these steps: (a) Create a start bit condition, (b) clock 9 cycles, (c)
create another start bit followed by stop bit condition as shown below. The device is ready for
next communication after above steps have been completed.
Figure 3-1. Software reset
Start bit
Dummy Clock Cycles
Start bit
Stop b
SCL
1
2
3
8
9
SDA
6 AT24C02B
5126H–SEEPR–8/07