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

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