6 - 4 SYNCHRONOUS COUNTERS
Synchronous counters arc different from ripple counters in that clock pulses arc applied to the
inputs of all flip-flops.A common clock triggers all flip-flops simultaneously. rather than one
at a time in succession as in a ripple counter. The dec ision whether a flip- flop is to be
complemented is dete rmined from the values of the data inputs. such as T or J and K at the time
of the cloc k edge. If T ::: 0 or j ::: K ::: O. the flip-flop doe s not change state. If T ::: I or
J ::: K ::: I. the flip-flop complements.
The design proced ure for synchronous counters was presented in Section 5.8. and the design
of a three-bit binary counter was carried out in conjunction wi th Fig. 5.31. In this section. we
present some typical synchronous counters and explain their operation.