6

Atmel AT24C128C [DATASHEET]

8734B–SEEPR–9/2012

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

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

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 6-2).

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 acknowledge that it has received each word.

Standby Mode: AT24C128C 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.

SDA

SCL

Data

Change

Data Stable

Data Stable

SDA

SCL

Start

Stop