ABSTRACT
Counters are versatile and useful for many applications in digital test instrumentation, such as digital multimeters, pulse counters, and frequency division. An obvious application of a counter is in the construction of a digital clock. A register is a collection of flip-flops designed to store binary data. A single flip-flop used as a register is often called a flag. Counters are classified as either synchronous or asynchronous. In synchronous binary counters, the system clock drives the control inputs to all the latches or flip-flops in the counter, and they all change state at the same time. A synchronous binary counter has all of its flip-flop clock inputs connected to the same common clock signal so that all its flip-flops change state at the same time, with a propagation delay of one flip-flop. Modulo-n or divide-by-n ripple counters are commercially available which can be user programmed to obtain any desired modulus.
