Page 140 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

Using Primitive Logic Functions to Build More Complex Functions 121

that these are edge-sensitive inputs. A chevron without an associated bobble
indicates a positive-edge clock, and a chevron with a bobble indicates a negative-
edge clock. The last rows in the truth tables show that an inactive edge on the
clock leaves the contents of the flip-flops unchanged (these cases are often
omitted from the truth tables).
Consider an example waveform for a positive-edge triggered D-type flip-flop
(Figure 11-16). As the observer initially has no knowledge as to the contents of
the flop-flop, the q and -q outputs are initially shown as having X, or don’t know,
values.

in this example). Meanwhile,
h is disabled and continues
.. .
output) its existing contents.
..
. a .

have an active-high enable. Both of thes md continues to store (and output) its
:xisting contents. Meanwhile the slave
atch is now enabled and passes whate
ralue is presented to its data input (the
e-, - ~ * t La.-.
II
1
.
macrer
iue rrom xne OUTDUT OT me iarcn
- --- - - - . _. - . . . _- - -. . -. - -. . I
.. r outputs
brything i
lek, but from the outside
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