PixArt Imaging Inc.
PAW3102DB
CMOS Optical Mouse Sensor
6. Serial Interface
The synchronous serial port is used to set and read parameters in the mouse sensor.
SCLK: The serial clock line. It is always generated by the mouse controller.
SDIO: The serial data line is used to write and read data.
6.1 Transmission Protocol
The transmission protocol is a two-wire link, half duplex protocol between the mouse controller and the mouse
sensor. All data changes on SDIO are initiated by the falling edge on SCLK. The mouse controller always
initiates communication; the mouse sensor never initiates data transfers.
The transmission protocol consists of the two operation modes:
- Write Operation.
- Read Operation.
Both of the two operation modes consist of two bytes. The first byte contains the address (seven bits) and has a
bit7 as its MSB to indicate data direction. The second byte contains the data.
S E C O N D B Y T E
F IR S T B Y T E
R/W
(1 B IT )
A D D R E S S (7 B IT )
D A T A (8 B IT )
L S
M S B
L S B M S B
Figure 7. Transmission Protocol
6.1.1 Write Operation
A write operation, which means that data is going from the mouse controller to the mouse sensor, is always
initiated by the mouse controller and consists of two bytes. The first byte contains the address (seven bits) and
has a “1” as its MSB to indicate data direction. The second byte contains the data. The transfer is synchronized
by SCLK. The mouse controller changes SDIO on falling edges of SCLK. The mouse sensor reads SDIO on
rising edges of SCLK.
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
SCLK
SDIO
DON'T
CARE
DON'T
CARE
1
A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
SDIO driven by the mouse controller
Figure 8. Write Operation
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
15
V1.2, April. 2008
PIXART [ PIXART IMAGING INC. ]
