Parallax 28560 Manual page 11

A typical flowchart for operating the chip is as follows:
Power on and wait
100 msec.
Set resolution in
register $1B.
Read status register
($16).
No
Motion
detected?
Yes
Read DX ($02) and
DY ($03) registers.
Update X and Y
values.
Communication with the chip takes place via two-wire (clock and data) serial I/O. The clock line is
normally high and pulses low to transfer data bits in or out of the chip.
Reading Data from the Sensor Registers
Data reads take place by setting the data line to an output, then sending the register address as eight
bits, most significant bit first, with bit 7 cleared to zero. Then the data line is switched to an input, and
eight bits of data are clocked out of the chip, most significant bit first:
Writing Data to the Sensor Registers
Data writes take place by setting the data line to an output, then sending the register address as eight
bits, most significant bit first, with bit 7 set to 1. Then eight data bits are clocked into the chip, most
significant bit first.
Copyright © Parallax Inc. Mouse Sensor Kit (#28560) v1.0 6/1/2010 Page 11 of 18