Ring counter is a type of counter that is composed of a shift register with clear and preset inputs provided externally. It is of two types: 1. Straight Ring Counter : Straight ring counter is a type of ring counter in which the output of the last flip-flop is connected to the input of the first flip-flip. It circulates a single ‘0’ or ‘1’ bit around the ring. 
2. Twisted Ring Counter : Twisted ring counter is a types of ring counter in which the complement of output of the last shift register is connected to the input of the first register. It circulates a stream of 1s followed by 0s around the ring. 
Difference between Straight and Twisted Ring Counter:
| STRAIGHT RING COUNTER | TWISTED RING COUNTER |
|---|
| It connects the output of the last shift register to the input of first shift register. | It connects the complement of output of the last shift register to the input of the first register. |
| It is known as One hot counter. | It is known as Walking ring counter or Johnson’s counter. |
| Number of states = number of flip-flops | Number of states = 2 x number of flip-flops |
| It circulates a single bit (0 or 1) around the ring. | It circulates stream of 1 followed by stream of 0. |
| PRESET is used in first shift register. | PRESET is not used in twisted ring counter. |
| CLEAR is used for last (n-1) flip-flops. | CLEAR is used for all flip-flips in it. |
| It is used in successive approximation and stepper motor control. | It is used in phase shift or function generator. |