AT24C64A データシートの表示（PDF） - Atmel Corporation

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AT24C64A

2-Wire Serial EEPROM

Atmel Corporation 

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 (refer to

Data Validity 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 (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 during the ninth clock cycle to

acknowledge that it has received each word.

STANDBY MODE: The AT24C32A/64A 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

two-wire part can be reset by following these steps:

(a) Clock up to 9 cycles, (b) look for SDA high in each cycle while SCL is high and then

(c) create a start condition as SDA is high.

6 AT24C32A/64A

3054T–SEEPR–1/07

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