4. 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 (refer to Data Valid-
ity 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 AT24C32C/64C 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.
SOFTWARE RESET: After an interruption in protocol, power loss or system reset, and 2-wire
part can be protocol 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 4-1. Software Reset
Dummy Clock Cycles
Start bit
Stop bit
Start bit
1
2
3
8
9
SCL
SDA
6
AT24C32C/64C
5298A–SEEPR–1/08
ATMEL [ ATMEL ]
