AT24C128B_14 Datasheet, PDF (6/23 Pages) ATMEL Corporation – Schmitt Trigger, Filtered Inputs for Noise Suppression

6. 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 6-1). Data
changes during SCL high periods will indicate a start or stop condition as defined below.
Figure 6-1. Data Validity
SDA
SCL
DATA STABLE
DATA STABLE
DATA
CHANGE
START CONDITION: A high-to-low transition of SDA with SCL high is a start condition that must
precede any other command (see Figure 6-2).
Figure 6-2. 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 6-2).
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 acknowledge
that it has received each word.
STANDBY MODE: The AT24C128B 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.
SOFTWARE RESET: After an interruption in protocol, power loss or system reset, any 2-wire
part can be protocol reset by following these steps: (a) Create a start bit condition, (b) clock 9
6 AT24C128B
5296A–SEEPR–1/08