Ripple counters have output bits not change states in synchronism. On the other hand, synchronous counters have their bits connected to the same CLK pulse.

However, I ran into circuits, which I thought it was a synchronous counter, noted as ripple counters in "Digital Systems" of Ronald Tocci.

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I just wonder if they are some other types of ripple counters?

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    \$\begingroup\$ The caption for Figure 7-8 is incorrect. The circuits shown are synchronous counters. \$\endgroup\$ – AlmostDone May 19 '18 at 10:46
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    \$\begingroup\$ The only funky thing is the asynchronous reset, but that doesn't make them "ripple" counters. It just makes the timing analysis messier. Plus, there's no guarantee that the reset pulse will reliably reset all of the FFs. This is another example of bad design from this book -- I'm starting to think that it should be avoided altogether. \$\endgroup\$ – Dave Tweed May 19 '18 at 11:26

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