AT24C256B_07 Datasheet, PDF (6/21 Pages) ATMEL Corporation – Two-wire Serial EEPROM 256K (32,768 x 8)

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 2).
Data changes during SCL high periods will indicate a start or stop condition as defined below.
Figure 2. Data Validity
START CONDITION: A high-to-low transition of SDA with SCL high is a start condition that
must precede any other command (see Figure 3).
Figure 3. Start and Stop Definition
SDA
SCL
START
STOP
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 3).
ACKNOWLEDGE: All addresses and data words are serially transmitted to and from the
EEPROM in 8-bit words. The EEPROM sends a “0” during the ninth clock cycle to acknowl-
edge that it has received each word.
STANDBY MODE: The AT24C256B features a low-power standby mode that is enabled upon
power-up and after the receipt of the stop bit and the completion of any internal operations.
6 AT24C256B
5080B–SEEPR–1/07