Synchronous and Asynchronous

  Shift register counters are shift registers with feedback that exhibit special sequences. Examples are the Johnson counter and the ring counter. The Johnson counter has 2n states in its sequence, where n is the number of stages. The ring counter has n states in its sequence.   Discuss the differences between the two main categories of counters: Synchronous Asynchronous Do some research and list your references - then discuss the concept of "“Metastability"” as it relates to digital counters. Which category of counter (Synchronous or Asynchronous) is more susceptible to Metastability?