PixArt Imaging Inc.
PAW3102DB
CMOS Optical Mouse Sensor
6.1.2 Read Operation
A read operation, which means that data is going from the mouse sensor to the mouse controller, is always
initiated by the mouse controller and consists of two bytes. The first byte contains the address, is written by the
mouse controller, and has a “0” as its MSB to indicate data direction. The second byte contains the data and is
driven by the mouse sensor. The transfer is synchronized by SCLK. SDIO is changed on falling edges of SCLK
and read on every rising edge of SCLK. The mouse controller must go to a high Z state after the last address data
bit. The mouse sensor will go to the high Z state after the last data bit.
SCLK
SDIO
1
2
3
4
5
6
7
8
Hi-Z
9
10
11
12
13
14
15
16
Hi-Z
_
R/W bit of next
address
DON'T
CARE
0
A6 A5 A4 A3 A2 A1 A0
D7 D6
D5 D4 D3 D2 D1 D0
SDIO driven by the m ouse controller
SDIO driven by the m ouse sensor
Note "B"
Note "A"
1. The m ouse controller sends address to the m ouse sensor.
2. The m ouse controller releases and set SDIO to Hi-Z after the last address bit.
Note "A"
SCLK
SDIO
8
9
7
Hi-Z
A1
A0
D7
tH OLD
3us,m in
1. The m ouse sensor sends data to the m ouse controller .
Note "B"
2. The m ouse sensor releases and set SDIO to Hi-Z after the last data bit.
SCLK
SDIO
1
16
D0
_
Hi-Z
R/W bit of next address
SDIO driven by the m ouse controller
Figure 9. Read Operation
6.2 Re-Synchronous Serial Interface
If the mouse controller and the mouse sensor get out of synchronization, then the data either written or read from
the registers will be incorrect. In such a case, an easy way to solve this condition is to toggle the SCLK line from
high to low for least tRESYNC, and then MUST toggle it from low to high to wait at least tSIWTT to reach re-
synchronous the serial port. This method is called by “watchdog timer timeout”. The mouse sensor will reset the
serial port without resetting the registers and be prepared for the beginning of a new transmission.
tS IW TT
1
0
1
1
1
2
1
3
1
4
1
5
1
6
SC LK
1
2
3
4
5
6
7
8
9
tR E S Y N C
1us, m in
H i-Z
_
AD D R ESS (R /W )
SD IO
D ATA
Figure 10. Re-synchronous Serial Interface Using Watchdog Timer Timeout
Note that this function is disabled when the mouse sensor is in the power down mode. If the user uses this
function during the power down mode, it will get out of synchronization. The mouse sensor and the mouse
controller also might get out of synchronization due to following conditions.
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
16
V1.2, April. 2008
PIXART [ PIXART IMAGING INC. ]
