13

Synchronous Serial Port

The synchronous serial port is used to set and read pa-

rameters in the ADNS-3000, and to read out the motion

information. The port is a four wire serial port. The host

micro-controller always initiates communication; the

ADNS-3000 never initiates data transfers. SCLK, MOSI, and

NCS may be driven directly by a micro-controller. The port

pins may be shared with other SPI slave devices. When the

NCS pin is high, the inputs are ignored and the output is

at tri-state.

The lines that comprise the SPI port:

SCLK: Clock input. It is always generated by the master

(the micro-controller).

MOSI: Input data. (Master Out/Slave In)

MISO: Output data. (Master In/Slave Out)

NCS: Chip select input (active low). NCS needs to be low to

activate the serial port; otherwise, MISO will be high

Z, and MOSI & SCLK will be ignored. NCS can also be

used to reset the serial port in case of an error.

Chip Select Operation

The serial port is activated after NCS goes low. If NCS is

raised during a transaction, the entire transaction is

aborted and the serial port will be reset. This is true for

all transactions. After a transaction is aborted, the normal

address-to-data or transaction-to-transaction delay is

still required before beginning the next transaction. To

improve communication reliability, all serial transactions

should be framed by NCS. In other words, the port should

not remain enabled during periods of non-use because

ESD and EFT/B events could be interpreted as serial com-

munication and put the chip into an unknown state. In ad-

dition, NCS must be raised after each burst-mode transac-

tion is complete to terminate burst-mode. The port is not

available for further use until burst-mode is terminated.

Power Management Modes

The ADNS-3000 has three power-saving modes. Each

mode has a different motion detection period with its

respective response time to mouse motion. Response

Time is the time taken for the sensor to ‘wake up’ from rest

mode when motion is detected. When left idle, the sen-

sor automatically changes or downshift from Run mode

to Rest1, to Rest2 and finally to Rest3 which consumes the

least current. Do note that current consumption is the low-

est at Rest3 and highest at Rest1, however time required

for sensor to respond to motion from Rest1 is the short-

est and longest from Rest3. Downshift Time is the elapsed

time (under no motion condition) from current mode to

the next mode for example, it takes 10s for the sensor that

is in Rest1 to change to Rest2. The typical response time

and downshift time for each mode is shown in the fol-

lowing table. However, user can change the default time

setting for each mode via register 0x0e through 0x13.

Mode

Response Time

(Typical)

Downshift Time

(Typical)

Rest 1

20 ms

<1 s

Rest 2

100 ms

10 s

Rest 3

500 ms

600 s

Note:

These default timings are subject to changes after characterization.

Another feature in ADNS-3000 that can be used to opti-

mize the power consumption of the optical mouse system

is the Motion Interrupt Output or MOTION pin (pin 3). It

allows the host controller to be in sleep mode (or low-

est operating current mode) when there is no motion

detected after some time instead of consistently be in

active mode and polling motion data from the sensor.When

motion is detected, the sensor will send the motion inter-

rupt signal through pin 3 to the controller to wake it up

from sleep mode to resume its motion detection routine

for navigation position and direction update.

MOTION Detection Routine

Typically in the motion detection routine, MCU will poll

the sensor for valid motion data by checking on the

MOTION_ST bit in MOTION_ST register. If MOTION_ST bit

is set, motion data in DELTA registers is valid and ready to

be read by the MCU. For 8-bit motion reporting the DELTA

registers are DELTA_X and DELTA_Y and for 12-bit motion

reporting the DELTA registers are DELTA_X, DELTA_Y and

DELTA_XY_HIGH.

MOTION Function

MOTION output signal (pin 3) can be used as interrupt in-

put to the microcontroller of the mouse to trigger the con-

troller to read the motion data from the sensor whenever

there is motion detected by the sensor. The MOTION signal

can be configured to be level or edge triggered, active

high or low by setting the bits in MOTION_CTRL register.

For active high level-triggered configuration, the MOTION

pin level will be driven high as long the MOTION bit in

register 0x02 is set and there is motion data in DELTA

registers ready to be read by the microcontroller. Once

all the motion data has been read, DELTA registers value

become zero, MOTION bit is reset and the MOTION pin

level is driven low.

For active high edge-triggered configuration, a pulse of

380ns (typical) will be sent through the MOTION pin when

there is motion detected by the sensor during rest modes.

The pulse can be used as interrupt input to activate the

microcontroller from its sleep mode to enter into run

mode to start polling the sensor for motion data by moni-

toring MOTION_ST bit (set whenever there is valid motion

data) in MOTION register (0x02) and reading DELTA regis-

ters until MOTION_ST bit is reset.

All rights strictly reserved any portion in this paper shall not be reproduced, copied or transformed to any other forms without permission.

PixArt Imaging Inc.

PixArt Imaging Inc.

ADNS-3000 Low Power Optical Mouse Sensor