6

Atmel AT24C256C

8568C–SEEPR–5/10

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 Figure 2). Data changes during SCL high periods

will indicate a start or stop condition as defined below.

Figure 4-1.

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 (refer to Figure 2-2).

Figure 4-2.

Start and Stop Definition

SDA

SCL

P

O

T

S

T

R

A

T

S

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 Figure 3).

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 Atmel

and after the receipt of the stop bit and the completion of any internal operations.