Equation-to-Minterm
Conversion
An example of converting an equation
to
minterm format
in
order to derive the select
code is given below:
D =
AB
+
AC
(Starting equation)
D =
AB
(C
+
C)
+ AC
(B
+
B)
(Multiplying by
1)
D = ABC + ABC +
ABC
+ ABC (Final minterms)
This final form contains only terms
that
contain all of the input sources. These are the
min terms you use. These min terms are selected with the minterm enable bits
LF7-LFO
as shown below:
ABC
ABC
ABC
ABC
ABC ABC
ABC
ABC
(Available
minterms)
(BLTCONO
1
1
0 0
1 0 1
0
LF 7-0 code
in
binary
C
A
LF 7-0 code
in
hex
DESIGNING
THE
LF
CONTROL
BYTE
WITH
VENN
DIAGRAMS
You can use Venn diagrams as an aid
in
selecting minterms. The Venn diagram
in
figure
6-3
shows a set of three circles labeled
A,
Band
C. In the diagram, the numbers 0
through 7
in
various areas correspond to the min term numbers shown
in
the preceding
section.
To
select which min terms are necessary to produce a certain kind of equation result, you
need only examine the circles and their intersections and copy down the numbers seen
there.
Blitter Hardware
175
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