Ring counter: considering 4 – bit Ring counter.

A typical application of shift register called as Ring counter.

• The o/p of FF-3 is connected to data i/p Do of FFO.

Working of Ring counter:

Initially a negative going pulse is applied to all flip flops, in effect as the figure it is applied as pre-set i/p to FFO and clear i/p to reset of the flip flops.

$\therefore$ Initial o/p of flip flops can be seen as

Now on every clock edge the o/p of $Q_o$ gets shifted to flip flop 1. o/p of flip flop 1 gets shifted to flip flops 2 and so on.

• At o/i of Ring counter we get a special pattern as shown below.

• 4 bit ring counter counts 4 clock pulses hence also called as 4:1 counter.

• It divides incoming frequency by 4.

In general N – bit ring counter can be considered as N : 1 counter, it can count ‘N’ pulses and

OR $frequency = \frac{fin}{N}$