X9252 Xicor, X9252 Datasheet - Page 12

• Manufacturer Part Number: X9252
• Description: Quad Digitally-Controlled (XDCP) potentiometer
• Manufacturer: Xicor

2-WIRE SERIAL INTERFACE
Protocol Overview
The device supports a bidirectional bus oriented
protocol. 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 called the master and the device being
controlled is called the slave. The master always
initiates data transfers, and provides the clock for both
transmit and receive operations. The X9252 operates
as a slave in all applications.
All 2-wire interface operations must begin with a
START, followed by a Slave Address byte. The Slave
Address selects the X9252, and specifies if a Read or
Write operation is to be performed.
All Communication over the 2-wire interface is
conducted by sending the MSB of each byte of data
first.
Figure 2. Valid Data Changes, Start, and Stop Conditions
REV 1.4.1 7/29/03
SDA
SCL
START
STABLE CHANGE
DATA
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DATA
STABLE
Serial Clock and Data
Data states on the SDA line can change only while
SCL is LOW. SDA state changes while SCL is HIGH
are reserved for indicating START and STOP
conditions. See Figure 2. On power up of the X9252,
the SDA pin is in the input mode.
Serial Start Condition
All commands are preceded by the START condition,
which is a HIGH to LOW transition of SDA while SCL is
HIGH. The device continuously monitors the SDA and
SCL lines for the START condition and does not
respond to any command until this condition has been
met. See Figure 2.
Serial Stop Condition
All communications must be terminated by a STOP
condition, which is a LOW to HIGH transition of SDA
while SCL is HIGH. The STOP condition is also used to
place the device into the Standby power mode after a
read sequence. A STOP condition can only be issued
after the transmitting device has released the bus. See
Figure 2.
DATA
STOP
X9252
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