Page 142 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

Using Primitive Logic Functions to Build More Complex Functions W 123

I I
data 4 data 4

clock > -4 clock > -4

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0 0

Asynchronous Clear 5ynchronous Clear

Figure 1 1-1 7. D-type flip-flops with asynchronous
and synchronous clear inputs

JK and T Flip-flops
The majority of examples in this book are based on D-type flip-flops.
However, for the sake of completeness, it should be noted that there are
several other flavors of flip-flops available. Two common types are the JK
and T (for Toggle) flip-flops (Figure 1 1 - 18).
The first row of the JK flip-flop’s truth table shows that when both the j
and k (data) inputs are 0, an active edge on the clock input leaves the contents
of the flip-flop unchanged. The two middle rows of the truth table show that if
the j and k inputs have opposite values, an active edge on the clock input will
effectively load the flip-flop (the q output) with the value on j (the -q output
will take the complementary value). The last line of the truth table shows
that when both the j and k inputs are 1, an active edge on the clock causes the
outputs to toggle to the inverse of their previous values.8 By comparison, the

This may be the origin of the term “flip-flop,” because the outputs flip and flop back and forth.