PixArt Imaging Inc.
PAN101B
CMOS Optical Navigation Sensor
7. Serial Interface
The synchronous serial port is used to set and read parameters in the PAN101B, and can be used to read
out the motion information instead of the quadrature data pins.
SCLK: The serial clock line. It is always generated by the host micro-controller.
SDIO: The serial data line used for write and read data.
PD:
A third line is sometimes involved. PD (Power Down pin) is usually used to place the PAN101B
in a low power mode to meet USB suspend specification. PD can also be used to force re-
synchronization between the micro-controller and the PAN101B in case of an error.
7.1 Transmission Protocol
The transmission protocol is a two-wire link, half duplex protocol between the micro-controller and
PAN101B. All data changes on SDIO are initiated by the falling edge on SCLK. The host micro-
controller always initiates communication; the PAN101B 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.
SECOND BYTE
FIRST BYTE
R /W
(1 BIT)
ADDRESS (7 BIT)
DATA (8 BIT)
LSB
MSB
LSB MSB
Figure 12. Transmission Protocol
7.1.1 Write Operation
A write operation, which means that data is going from the micro-controller to the PAN101B, is always
initiated by the micro-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 micro-controller changes SDIO on falling edges of SCLK. The PAN101B
reads SDIO on rising edges of SCLK.
SCLK
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
DON'T
CARE
DON'T
CARE
SDIO
1
A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
SDIO driven by Micro-controller
Figure 13. Write Operation
7.1.2 Read Operation
A read operation, which means that data is going from the PAN101B to the micro-controller, is always
initiated by the micro-controller and consists of two bytes. The first byte contains the address, is written
by the micro-controller, and has a “0” as its MSB to indicate data direction. The second byte contains the
data and is driven by the PAN101B. The transfer is synchronized by SCLK. SDIO is changed on falling
edges of SCLK and read on every rising edge of SCLK. The micro-controller must go to a high Z state
after the last address data bit. The PAN101B will go to the high Z state after the last data bit.
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13
V1.4, FEB. 2003
PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
PIXART [ PIXART IMAGING INC. ]
