Ring Shift Counter and Johnson Shift Counter

Ring shift counters and Johnson shift counters are used to generate sequential control waveforms.
The Ring shift counter is a recirculating register in which the serial output is connected back to the serial input.
The Q outputs of the Ring shift counter will go high for one clock pulse one at a time in sequence.
The Ring shift counter must be initially set-up with a single flip-flop set and all others reset.
The initial condition of the Ring shift counter will be shifted through the register on each clock pulse.
The Ring counter can be made with either D-type or J-K Flip-Flops.

The Johnson shift counter has the recirculating lines crossed such that the inverse of the output data is fed back to the input.
Each Q output of the Johnson shift counter is a square wave (50% duty cycle).
Each Q output of the Johnson shift counter is offset or shifted by one clock pulse.
The Johnson shift counter must be initially reset (all flip-flops zero).
The Johnson counter is also called a Twisted Ring counter.