Synchronous Up-Down Counters

Synchronous

Up-Down Counters

A circuit of a 3-bit synchronous up-down counter and a table of its sequence are shown below.  Similar to an asynchronous up-down counter, a synchronous up-down counter also has an up-down control input.  It is used to control the direction of the counter through a certain sequence.
3-bit Synchronous Up-Down Counter
SequenceAn examination of the sequence table shows:
  • for both the UP and DOWN sequences, Q0 toggles on each clock pulse.
  • for the UP sequence, Q1 changes state on the next clock pulse when Q0=1.
  • for the DOWN sequence, Q1 changes state on the next clock pulse when Q0=0.
  • for the UP sequence, Q2 changes state on the next clock pulse when Q0=Q1=1.
  • for the DOWN sequence, Q2 changes state on the next clock pulse when Q0=Q1=0.
These characteristics are implemented with the AND, OR & NOT logic connected as shown in the logic diagram above.

Synchronous Up-Down Counters Synchronous Up-Down Counters Reviewed by Suresh Bojja on 9/09/2015 09:45:00 AM Rating: 5
Theme images by sebastian-julian. Powered by Blogger.