Dear Michel,

Thanks a lot for the link, I will use this for the internal representation, adding the unused bits to store the logical relationship

Erik,

I am speaking about a PLC just to give an idea about what I need to do... Look in the other branch to see what this stuff is all about... I am not trying to develop a PLC based on a 8051 uC, I just need that the logical relationship between port pins being programmable by the user and uploaded remotely, so I am looking for tips and ideas about the implementation of it in C.

cheers,
JLR