S524AD0XD1 Datasheet, PDF (6/16 Pages) Samsung semiconductor – 128K/256K-bit Serial EEPROM for Low Power

S524AD0XD1/D0XF1 SERIAL EEPROM
DATA SHEET
I²C-BUS PROTOCOLS
Here are several rules for I²C-bus transfers:
— A new data transfer can be initiated only when the bus is currently not busy.
— MSB is always transferred first in transmitting data.
— During a data transfer, the data line (SDA) must remain stable whenever the clock line (SCL) is High.
The I²C-bus interface supports the following communication protocols:
• Bus not busy: The SDA and the SCL lines remain in High level when the bus is not active.
• Start condition: A start condition is initiated by a High-to-Low transition of the SDA line while SCL remains in
High level. All bus commands must be preceded by a start condition.
• Stop condition: A stop condition is initiated by a Low-to-High transition of the SDA line while SCL remains in
High level. All bus operations must be completed by a stop condition (see Figure 8-7).
SCL
SDA
Start
Condition
Data or Data
ACK Valid Change
Stop
Condition
Figure 8-7. Data Transmission Sequence
• Data valid: Following a start condition, the data becomes valid if the data line remains stable for the duration
of the High period of SCL. New data must be put onto the bus while SCL is Low. Bus timing is one clock
pulse per data bit. The number of data bytes to be transferred is determined by the master device. The total
number of bytes that can be transferred in one operation is theoretically unlimited.
• ACK (Acknowledge): An ACK signal indicates that a data transfer is completed successfully. The transmitter
(the master or the slave) releases the bus after transmitting eight bits. During the 9th clock, which the master
generates, the receiver pulls the SDA line low to acknowledge that it has successfully received the eight bits
of data (see Figure 8-8). But the slave does not send an ACK if an internal write cycle is still in progress.
In data read operations, the slave releases the SDA line after transmitting 8 bits of data and then monitors
the line for an ACK signal during the 9th clock period. If an ACK is detected but no stop condition, the slave
will continue to transmit data. If an ACK is not detected, the slave terminates data transmission and waits for
a stop condition to be issued by the master before returning to its stand-by mode.
8-6