PixArt Imaging Inc.
PAS6167
CMOS Image Sensor IC
3. I2CTM Bus
PAS6167 supports I2C bus transfer protocol and acts as slave device. The 7-bits unique slave address is
“1000000” and supports receiving / transmitting speed as maximum 400KHz.
I2C Bus Overview
z
Only two wires SDA ( serial data ) and SCL ( serial clock ) carry information between the
devices connected to the I2C bus. Normally both SDA and SCL lines are open collector
structure and pulled high by external pull-up resistors.
z
z
Only the master can initiates a transfer ( start ), generates clock signals, and terminates a
transfer ( stop ).
Start and stop condition : A high to low transition of the SDA line while SCL is high defines a
start condition. A low to high transition of the SDA line while SCL is high defines a stop
condition. Please refer to Figure 2.1.
z
Valid data : The data on the SDA line must be stable during the high period of the SCL clock.
Within each byte, MSB is always transferred first. Read / Write control bit is the LSB of the
first byte. Please refer to Figure 2.2.
z
z
Both the master and slave can transmit and receive data from the bus.
Acknowledge : The receiving device should pull down the SDA line during high period of the
SCL clock line when a complete byte was transferred by transmitter. In the case of a master
received data from a slave, the master does not generate an acknowledgment on the last byte
to indicate the end of a master read cycle.
Figure 2.1 Start and Stop conditions
Figure 2.2 Valid Data
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
V1.0, 2009/08/12
PIXART [ PIXART IMAGING INC. ]
