DESIGNING THE LF CONTROL BYTE WITH VENN DIAGRAMS
Another way to arrive at a particular function is through the use of Venn diagrams:
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
- 172 Blitter Hardware -
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