Serial Clock (SCL)
The SCL input is used to clock all data into and out of the
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and
out of the device. It is a push/pull output and does not
require the use of a pull-up resistor.
3836 PGM T01
The X24C00 supports a bidirectional bus oriented pro-
tocol. The protocol defines any device that sends data
onto the bus as a transmitter and the receiving device as
the receiver. The device controlling the transfer is a
master and the device being controlled is the slave. The
master will always initiate data transfers and provide the
clock for both transmit and receive operations. There-
fore, the X24C00 will be considered a slave in all
Clock and Data Conventions
Data states on the SDA line can change only during SCL
LOW. SDA state changes during SCL HIGH are re-
served for indicating start and stop conditions. Refer to
Figures 1 and 2.
All commands are preceded by the start condition,
which is a HIGH to LOW transition of SDA when SCL is
HIGH. The X24C00 continuously monitors the SDA and
SCL lines for the start condition and will not respond to
any command until this condition has been met.
A start may be issued to terminate the input of a control
word or the input of data to be written. This will reset the
device and leave it ready to begin a new read or write
command. Because of the push/pull output, a start
cannot be generated while the part is outputting data.
Starts are also inhibited while a write is in progress.
The stop condition is a LOW to HIGH transition of SDA
when SCL is HIGH. The stop condition is used to reset
the device during a command or data input sequence
and will leave the device in the standby mode. As with
starts, stops are inhibited when outputting data and
while a write is in progress.
The byte write operation is initiated with a start condition.
The start condition is followed by an eight bit control byte
which consists of a two bit write command (0,1), four
address bits, and two “don’t care” bits (Figure 3).