Owner manual

6
AT24C128/256
0670H–SEEPR–07/02
Device
Operation
CLOCK and DATA TRANSITIONS: TheSDApinisnormallypulledhighwithanexternal
device. Data on the SDA pin may change only during SCL low time periods (refer to Data
Validity timing diagram). 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 (refer to Start and Stop Definition timing diagram).
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 (refer to
Start and Stop Definition timing diagram).
ACKNOWLEDGE: All addresses and data words are serially transmitted to and from the
EEPROM in 8-bit words. The EEPROM sends a zero during the ninth clock cycle to acknowl-
edge that it has received each word.
STANDBY MODE: The AT24C128/256 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.
MEMORY RESET: After an interruption in protocol, power loss or system reset, any 2-wire
part can be reset by following these steps: (a) Clock up to 9 cycles, (b) look for SDA high in
each cycle while SCL is high and then (c) create a start condition as SDA is high.