The main building block of the programmable devices we use in the TM-2a is a Logic Element (or LE). The only parts of the LE that we use are the LUT, Cascade chain and programmable register (or FF).
    Note that it is not necessary to use all of these elements. The FFs and LUTs can be used independently. However, if one wants to use both a LUT and a FF in the same LE they have to be connected in the order shown.