PixArt Imaging Inc.

PAN101B

CMOS Optical Navigation Sensor

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PixArt Imaging Inc.

V1.4, FEB. 2003

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.

ADDRESS (7 BIT)

DATA (8 BIT)

FIRST BYTE

SECOND BYTE

MSB

LSB

R/W

(1 BIT)

MSB

LSB

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.

SDIO driven by Micro-controller

SCLK

SDIO

1

2

345

678

10

A5

A4

A3

A2

A1

A0

D7

D6

D5

D4

D3

D2

D1

D0

9

11

12

13

14

15

A6

DON'T

CARE

1

DON'T

CARE

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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.

Figure 12. Transmission Protocol

Figure 13. Write Operation