PixArt Imaging Inc.

PAS6371LT

CMOS Image Sensor IC

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7

PixArt Imaging Inc.

V1.1,

2008/04/09

4.

I2C

PAS6371LT 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

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.

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.

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.

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