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What Is a Ring Counter?

Article Details
• Written By: Jean Marie Asta
• Edited By: Jessica Seminara
2003-2017
Conjecture Corporation
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In a computer system, the standard ring counter form is a type of counter that is composed of a shift register, another type of counter that exists in the sequential logic form. This type of logic is affected and determined by previous inputs and prior history of data. The registers produce discrete delays of waveforms or digital signals, which are synchronized to certain functions by a discrete and variable amount of stages in a shift register. These stages are called either flip-flops of type “D” or flip-flops of type “JK.” Shift registers once served as a computer’s digital memory, being up to hundreds of stages long.

Certain shift registers can become ring counters if a particular shift register’s output data is fed back into its input. In performing this action, this type of register is now considered a ring counter where the final flip-flop output data becomes the initial flip-flop input data of the register. The data in the counter loops continuously, re-circulating and repeating the data within this closed circuit. This kind of counter is called a straight ring counter or an overbeck counter.

In a straight ring counter that consists of 4 bits, the circuit works by binary code, with each bit being set at either 1 or 0, with sets of functions that reset each bit with every flip-flop. Working in this manner, when the first bit sets to 1, all other bits set to 0. With each consecutive flip flop, the next bit that follows is set to 1 while the bit that was previously set at 1 becomes set at 0. This process continues in this counter for 4 flip-flops until it reaches the last bit and starts over. The movement that this counter exhibits is called “rotational” because of its circular nature.

Another type of counter is called the twisted ring counter, also known by the names Johnson ring counter or Moebius counter. The feedback data of this type of counter is similar to the overbeck counter except that the final flip-flop output data is inverted and fed back into the initial flip-flop input. This counter is beneficial because it requires half the amount of flip-flops that an overbeck counter may require. In some instances, this type of counter may even operate twice as fast, thereby cutting operation time. The twisted ring counter is available as the standard forms of TTL or CMOS IC.