PixArt Imaging Inc.

PAS109B

CMOS Image Sensor IC

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8

PixArt Imaging Inc.

V1.1, Mar. 2002

5.2.2 Slave transmits data to master (read cycle)

The sub-address was taken from previous write cycle

The sub-address is automatically increment after each byte read

Am : Acknowledge by master

Note there is no acknowledgment from master after last byte read

During read cycle, the master generates start condition and then place the 1

slave address (7 bits) with a read/write control bit to SDA line. After issue acknowledgment, 8 bits DATA was

also placed on SDA line by PAS109B. The 8 bit data was read from PAS109B internal control register that

address was assigned by previous write cycle. Follow the master acknowledgment, the PAS109B place the next 8

bits data (address is increment automatically) on SDA line and then transmit to master serially. The DATA and

Am cycles is repeat until the last byte read. After last byte read, Am is no longer generated by master but instead

by keep SDA line high. The slave (PAS109B) must releases SDA line to master to generate STOP condition.

(Please refer to Fig 5.3.)

Fig 5.3 Data Transfer Format

S

SLAVE ADDRESS

(7 BITS)

RW

A

DATA (8 BIT)

Am

DATA

1

P

1ST BYTE

2ND BYTE

n BYTE

NO ACK IN LAST

BYTE

Am

DATA

SDA

SCL

S

Start

Condition

1-7

8

9

1-7

8

9

1-7

8

9

P

Stop

Condition

ACK

from

Receiver

Data

ACK

from

Receiver

Data

ACK

from

Receiver

R/W

Address