In Example 7-3, a MOD-60 counter was needed to divide the 60-Hz line frequency down to 1 Hz. Construct an appropriate MOD-60 counter.

Data from Example 7-3

The first step involved in building a digital clock is to take the 60-Hz signal and feed it into a Schmitt-trigger, pulse-shaping circuit* to produce a square wave, as illustrated in Figure 7-3. The 60-Hz square wave is then put into a MOD-60 counter, which is used to divide the 60-Hz frequency by exactly 60 to produce a 1-Hz waveform. This 1-Hz waveform is fed to a series of counters, which then count seconds, minutes, hours, and so on. How many FFs are required for the MOD-60 counter?