Reference        : RfMatrix
Author           : CJ international
Date of Creation : September 1993
Version number   : 1
Description      : ladder diagram equations
                   (completely programmed with LD language)

This project operates a (4,4) matrix of output leds. The 4 input
buttons on the left are used to light on / off the rows of the matrix.
The 4 input buttons on the right are used to light on / off the
columns of the matrix.

When a row and a column are switched on together, their
intersection point blinks.

Two LD programs are used to switch on and off the blinking leds.
An internal boolean variable is used to identify odd and even
target cycles. This variable is used to validate the execution of
one of these two programs.




