Another way to arrive at a particular function is through the use of Venn
diagrams:
                         ______  0 ______
                        /      \  /      \
                       /        \/        \
                      /         /\         \
                     /   A     /  \     B   \
                    |    -    |    |    -    |
                    |         |  6 |         |
                    |         |    |         |
                    |       4 |____| 2       |
                    |        /|    |\        |
                    |       / |  7 | \       |
                     \     /   \  /   \     /
                      \   /  5  \/  3  \   /
                       \ |      /\      | /
                        \|_____/  \_____|/
                         |              |
                         |       1      |
                         |              |
                         |              |
                          \            /
                           \     C    /
                            \    -   /
                             \______/

             Figure 6-3: Blitter Minterm Venn Diagram


1. To select a function D=A (that is, destination = A source only),
   select only the  minterms  that are totally enclosed by the A-circle in
   the Figure above.  This is the set of  minterms  7, 6, 5, and 4. When
   written as a set of 1s for the selected  minterms  and 0s for those not
   selected, the value becomes:

               Minterm Number      7 6 5 4 3 2 1 0
               Selected Minterms   1 1 1 1 0 0 0 0
                                  -----------------
                                        F   0       equals $F0

2. To select a function that is a combination of two sources, look for
   the  minterms  by both of the circles (their intersection).  For
   example, the combination AB (A "and" B) is represented by the area
   common to both the A and B circles, or  minterms  7 and 6.

               Minterm Numbers     7 6 5 4 3 2 1 0
               Selected Minterms   1 1 0 0 0 0 0 0
                                  -----------------
                                        C   0       equals $C0

3. To use a function that is the inverse, or "not", of one of the sources,
           _
   such as A,

   take all of the  minterms  not enclosed by
   the circle represented by A on the above Figure.  In this case, we
   have  minterms  0, 1, 2, and 3.

               Minterm Numbers     7 6 5 4 3 2 1 0
               Selected Minterms   0 0 0 0 1 1 1 1
                                  -----------------
                                        0   F       equals $0F

4. To combine  minterms , or "or" them,  "or" the values together. For
   example, the equation AB+BC becomes

               Minterm Numbers     7 6 5 4 3 2 1 0
               AB                  1 1 0 0 0 0 0 0
               BC                  1 0 0 0 1 0 0 0
              -------------------------------------
               AB+BC               1 1 0 0 1 0 0 0
                                        C   8       equals $C8