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 (see Figure 4-3 on
page 7). 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 4-4 on page 7).
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 4-4 on page 7).
ACKNOWLEDGE: All addresses and data words are serially transmitted to and from the
EEPROM in 8-bit words. The EEPROM sends a zero to acknowledge that it has received each
word. This happens during the ninth clock cycle.
STANDBY MODE: The AT34C02C features a low-power standby mode which is enabled: (a)
upon power-up or (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.
Figure 4-1. Bus Timing SCL: Serial Clock SDA: Serial Data I/O
6 AT34C02C
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