PS/2 Protocol
The PS/2 protocol allows synchronous, bi-directional serial communication between the host and the device. Either side may transmit a command or data byte at any time, although only one side can transmit at one time. During initialization, the host sends command bytes to the device. Some commands are followed by argument bytes. The device acknowledges each command and argument byte with an ACK ($FA) byte, possibly followed by one or more data bytes. If the host has enabled "Stream mode" transmission, then the device may send spontaneous data packets to the host describing finger motions and button state changes.

FEATUREs
● Low-cost solution for PS/2 4D mouse
● Compatible with Microsoft IntelliMouse
● I/O ports
   - 8 special purpose I/O pins optimized for photo-sensor
   - 2 I/O pins with LED drive capability
● Patent pending full-range detection for photo-sensor
   - Removes the expensive process of matching LED and photo-sensor
   - Improve end-product yield rate almost to 100%
   - Huge cost saving
● Option to use wheel or button for scrolling
● Option to detect 2 or 4 pulses for one move
● R-C oscillator
   - No expensive crystal oscillator required
   - Reduce BOM
● Improved output drivers with slew-rate control to reduce EMI
● Minimal external components(2R or 3R + 2C) required for application circuit
● Tracking speed
   - Up to 100ms/per sampling
● 6 MHz external clock
● Internal power-on reset(POR)
● Available in cost saving 16-pin PDIP