# Types Of Counter || Registers and Counters || Bcis Notes

## Types Of Counter

The main purpose of the counter is to record the number of occurrence of some input. There are many types of counter both binary and decimal.

### Counter

The counter is a sequential circuit. A digital circuit which is used for counting pulse is known as a counter. It is the widest application of flip-flops. It is a group of a flip-flop with clock signal applied. Counter are two types.
– Asynchronous counter
– Synchronous counter

Difference between Asynchronous and Synchronous

 Asynchronous counter OR Ripple counter Synchronous counter Flip-flips are connected in a such a way that the output of first flip-flop drives the clock of next flip-flop. There is no connection between the output of the first flip-flop and clock of next flip-flop. Flip-flops are not clocked simultaneously. All the flip-flops are clocked simultaneously. Less number of logic gates are required. A large number of logic gates are required. Speed is slow as the clock is propagated though no: of the stage. Speed is high as the clock is given at the same time. It is slow in operation. It is faster than a ripple counter in operation. Low cost High cost

Features of Asynchronous counter.

• These are very simple in design.
• As it’s designed is simple they use less number of logic gates to construct asynchronous counter.
• Operation of the asynchronous counter is very low as compare to synchronous counter.

Types of Asynchronous counter.

• UP counter.
• Down counter.
• Equal Up-down counter.
• Ripple BCD counter.

Two-bit asynchronous counter

The figure shows that the two-bit counter connected for the asynchronous counter. Notice that the clock is applied to the clock input of only first flip-flop, which is always the less significant bit. The second flip-flop triggered by the (Ǭ0) output of the first flip-flop edge of (Ǭ0) output of the flip-flop. Because of inherent propagation delay time through a flip-flop. A transition of the input clock pulse and transition of Ǭ0 output can never exactly occur at the same time. Therefore two flip-flops are simultaneously triggered, so the counter operation is asynchronous which is also called ripple counter.

Binary state sequence table for the counter

 Clock pulse Q1 Q2 Initially 0 0 1 0 1 2 1 0 3 1 1 4(Recycle) 0 0

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