A ring counter is a type of counter composed of a type circular shift register. The output of the last shift register is fed to the input of the first register. The hamming distance of a Johnson counter is 1, the hamming distance of an Overbeck counter is 2.
There are two types of ring counters:
- A straight ring counter or Overbeck counter connects the output of the last shift register to the first shift register input and circulates a single one (or zero) bit around the ring. For example, in a 4-register one-hot counter, with initial register values of 1000, the repeating pattern is: 1000, 0100, 0010, 0001, 1000... . Note that one of the registers must be pre-loaded with a 1 (or 0) in order to operate properly.
- A twisted ring counter, also called Johnson counter or Möbius counter (also Moebius), connects the complement of the output of the last shift register to the input of the first register and circulates a stream of ones followed by zeros around the ring. For example, in a 4-register counter, with initial register values of 0000, the repeating pattern is: 0000, 1000, 1100, 1110, 1111, 0111, 0011, 0001, 0000... .
Read more about Ring Counter: Four-bit Ring Counter Sequences, Johnson Counter(4-bits), Applications
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