A decade counter is a type of digital counter circuit that is designed to count sequentially through a series of ten states. Each state represents a unique binary value, ranging from 0000 to 1001 in binary (0 to 9 in decimal). It's primarily used for applications where you need to count from 0 to 9 or 9 to 0 in a cyclic manner, such as in digital clocks, timers, frequency dividers, and other similar devices.
A decade counter is usually built using flip-flops and logic gates, and it advances to the next state each time a clock pulse is received. When it reaches the highest count (9 in a 4-bit counter), it wraps around to 0 on the next clock pulse, restarting the counting cycle.
The term "decade" in "decade counter" refers to its ability to count through ten distinct states, making it suitable for various counting and timing applications that involve intervals of ten. It's important to note that the counter can be designed to count higher by adding more bits to the counter circuit. For instance, a 4-bit decade counter can count from 0 to 9 (10 states), but a 6-bit counter can count from 0 to 63 (64 states), and so on, exponentially increasing the counting range with the addition of each bit.