Application Note AN1061
How to use 3×4 key matrix(keypad) for PC control
CPJexc
3×4 key matrix can be connected to the parallel port.
The key matrix is very simple but provides many buttons by very few wires.
The the diagram is as below.
Select “[P Ch]Key Matrix(3×4)” at the MISC tab.
And perform “Auto Detect” at setting page in the Button tab.
1. Click “Auto Detect”
2. Press the buttons one by one
3. Click “Auto Detect” again to finish auto-detection
You can use the key matrix as a key pad.
You can use the Rotary Encoder movement for application launching and switching. 
