16

Figure 13. Timing between write and read commands

Figure 14. Timing between read and either write or subsequent read commands

Address

Data

Write Operation

Address

Next Read Operation

SCLK

Next Read or

Write Operation

Data

Read Operation

Address

Address

SCLK

If the rising edge of SCLK for the last address bit of the

read command occurs before the tswr required delay,

the write command may not complete correctly. During

a read operation, SCLK should be delayed at least tSRAD

after the last address data bit to ensure that the sensor has

time to prepare the requested data.

The falling edge of SCLK for the first address bit of either

the read or write command must be at least tSRR or tSRW

after the last SCLK rising edge of the last data bit of the

previous read operation. In addition, during a read opera-

tion SCLK should be delayed after the last address data

bit to ensure that the sensor has time to prepare the re-

quested data.

Burst Mode Operation

Burst mode is a special serial port operation mode which

may be used to reduce the serial transaction time for three

predefined operations: motion read and PROM download

and frame capture. The speed improvement is achieved

by continuous data clocking to or from multiple regis-

ters without the need to specify the register address, and

by not requiring the normal delay period between data

bytes.

Motion Read

Reading the Motion_Burst register activates this mode.

The sensor will respond with the following motion burst

report in order.

BYTE[00] = Motion

BYTE[01] = Observation

BYTE[02] = Delta_X_L

BYTE[03] = Delta_X_H

BYTE[04] = Delta_Y_L

BYTE[05] = Delta_Y_H

BYTE[06] = SQUAL

BYTE[07] = Pixel_Sum

BYTE[08] = Maximum_Pixel

BYTE[09] = Minimum_Pixel

BYTE[10] = Shutter_Upper

BYTE[11] = Shutter_Lower

NOTE: Motion burst data can be read from the Motion_

Burst register even in run or rest mode.

After sending the register address, the micro-controller

must wait one frame, and then begin reading data. All

data bits can be read with no delay between bytes by driv-

ing SCLK at the normal rate. The data are latched into the

output buffer after the last address bit is received. After

the burst transmission is complete, the micro-controller

must raise the NCS line for at least tBEXIT to terminate

burst mode. The serial port is not available for use until

it is reset with NCS, even for a second burst transmission.

Procedure to start motion burst,

1. Lower NCS

2. Send 0x50 to Motion_Burst.

3. Wait for TSRAD.

4. Start reading SPI Data continuously up to 12bytes,

Motion burst may be terminated by pulling NCS high.

5. To read new motion burst data, repeat from step 1.

6. Write any value to Motion register to clear any residual

motion if desired.

PixArt Imaging Inc.

Track-on-Glass Laser Sensor

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PixArt Imaging Inc.