X4003/X4005
Figure 5. Valid Data Changes on the SDA Bus
SCL
SDA
Data Stable
Data Change
Data Stable
Serial Start Condition
Serial Stop Condition
All commands are preceded by the start condition,
which is a HIGH to LOW transition of SDA when SCL is
HIGH. The device continuously monitors the SDA and
SCL lines for the start condition and will not respond to
any command until this condition has been met. See
Figure 6.
All communications must be terminated by a stop condi-
tion, which is a LOW to HIGH transition of SDA when
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 6.
Figure 6. Valid Start and Stop Conditions
SCL
SDA
Start
Stop
Serial Acknowledge
The device will respond with an acknowledge after rec-
ognition of a start condition and the correct contents of
the slave address byte. Acknowledge bits are also pro-
vided by the X4003/4005 after correct reception of the
control register address byte, after receiving the byte
written to the control register and after the second
slave address in a read question (See Figure 8 and
See Figure 9.)
Acknowledge is a software convention used to indicate
successful data transfer. The transmitting device, either
master or slave, will release the bus after transmitting
eight bits. During the ninth clock cycle, the receiver will
pull the SDA line LOW to acknowledge that it received
the eight bits of data. Refer to Figure 7.
Characteristics subject to change without notice. 7 of 18
REV 1.1.3 4/30/02
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