When a pulse waveform is applied to the clock input of a J-K flip-flop that is connected to toggle, the Q output is a square wave with half the frequency of the clock input. If more flip-flops are connected together as shown in the figure below, further division of the clock frequency can be achieved.
The Q output of the second flip-flop is one-fourth the frequency of the original clock input. This is because the frequency of the clock is divided by 2 by the first flip-flop, then divided by 2 again by the second flip-flop. If more flip-flops are connected this way, the frequency division would be 2 to the power n, where n is the number of flip-flops.
In digital systems, data are normally stored in groups of bits that represent numbers, codes, or other information. So, it is common to take several bits of data on parallel lines and store them simultaneously in a group of flip-flops. This operation is illustrated in the figure below.
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Each of the three parallel data lines is connected to the D input
of a flip-flop. Since all the clock inputs are connected to the same
clock, the data on the D inputs are stored simultaneously by the flip-flops
on the positive edge of the clock.
Registers, a group of flip-flops use for
data storage, will be explained in more detail in a later chapter.
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| Another very important application of flip-flops is in digital
counters, which are covered in detail in the
next chapter.
A counter that counts from 0 to 3 is illustrated in the timing diagram
on the right. The two-bit binary sequence repeats every four clock
pulses. When it counts to 3, it recycles back to 0 to begin the sequence
again. |
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