What is a Johnson counter and how does it shift data?
1 Answer
A Johnson counter is a type of shift register, which is a digital circuit used to store and transfer data in a sequential manner. The Johnson counter, also known as a rotary ring counter or twisted ring counter, is a specific configuration of a shift register that has some unique characteristics.
In a Johnson counter, the shift register is designed in a "ring" or loop configuration. It consists of a series of flip-flops connected in a closed loop, with the output of the last flip-flop connected to the input of the first flip-flop, creating a circular shift pattern.
The counter can be constructed using either D flip-flops or JK flip-flops. The number of flip-flops in the Johnson counter determines the maximum number of states or the length of the counter sequence. A Johnson counter with 'n' flip-flops can represent 2^n different states.
The main feature of the Johnson counter is that, during each clock cycle, the data is shifted one position to the right or left depending on the design. The direction of the shift (right or left) is controlled by the clock signal. In a right-shift Johnson counter, data is shifted from the least significant bit (LSB) to the most significant bit (MSB), and in a left-shift Johnson counter, the data is shifted in the opposite direction, from MSB to LSB.
As the data is shifted in a circular pattern, the last bit that is shifted out (LSB in right-shift or MSB in left-shift) is fed back to the first flip-flop, completing the loop. This feedback mechanism allows the Johnson counter to cycle through all possible states before repeating the sequence.
Johnson counters have applications in various digital systems, including shift registers, frequency dividers, and waveform generators. They are used in situations where a repetitive sequence of states is required, and their unique shift pattern makes them useful for specific counting and encoding tasks.
In a Johnson counter, the shift register is designed in a "ring" or loop configuration. It consists of a series of flip-flops connected in a closed loop, with the output of the last flip-flop connected to the input of the first flip-flop, creating a circular shift pattern.
The counter can be constructed using either D flip-flops or JK flip-flops. The number of flip-flops in the Johnson counter determines the maximum number of states or the length of the counter sequence. A Johnson counter with 'n' flip-flops can represent 2^n different states.
The main feature of the Johnson counter is that, during each clock cycle, the data is shifted one position to the right or left depending on the design. The direction of the shift (right or left) is controlled by the clock signal. In a right-shift Johnson counter, data is shifted from the least significant bit (LSB) to the most significant bit (MSB), and in a left-shift Johnson counter, the data is shifted in the opposite direction, from MSB to LSB.
As the data is shifted in a circular pattern, the last bit that is shifted out (LSB in right-shift or MSB in left-shift) is fed back to the first flip-flop, completing the loop. This feedback mechanism allows the Johnson counter to cycle through all possible states before repeating the sequence.
Johnson counters have applications in various digital systems, including shift registers, frequency dividers, and waveform generators. They are used in situations where a repetitive sequence of states is required, and their unique shift pattern makes them useful for specific counting and encoding tasks.