Device Operation
CLOCK and DATA TRANSITIONS: The SDA pin is normally pulled high with an exter-
nal device. Data on the SDA pin may change only during SCL low time periods (see
Figure 4 on page 7). 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 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 Figure 5 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 AT24C01A/02/04/08A/16A 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:
1. Clock up to 9 cycles.
2. Look for SDA high in each cycle while SCL is high.
3. Create a start condition.
6
AT24C01A/02/04/08A/16A
0180V–SEEPR–8/05
ATMEL [ ATMEL ]
