A decade counter is a type of digital counter circuit that counts in decimal (base-10) format. It is a specific type of binary counter designed to count from 0 to 9 and then reset back to 0, completing one full decade (10 counts) for each clock pulse input. Each output of the counter represents a binary value equivalent to a decimal digit, hence the name "decade counter."
A typical decade counter has four output pins, which are used to represent the decimal digits 0 to 9. These output pins are typically labeled as Q0, Q1, Q2, and Q3. The counter advances from 0 (0000 in binary) to 1 (0001 in binary), 2 (0010 in binary), and so on, up to 9 (1001 in binary), and then resets back to 0 (0000 in binary) to start the next counting cycle.
To count higher than 9, multiple decade counters can be cascaded together. For example, if you cascade two decade counters, you can count from 0 to 99 (00 to 99 in decimal), using the first counter for the tens digit and the second counter for the ones digit. By cascading more decade counters, you can count even higher.
The maximum count achievable using a decade counter depends on the number of counters cascaded together and the specific counter configuration used in the circuit. For example, with two cascaded decade counters, you can count up to 99 (00 to 99 in decimal). With three cascaded decade counters, you can count up to 999 (000 to 999 in decimal), and so on.
Keep in mind that in practical applications, the maximum count is also limited by the clock frequency and the propagation delay of the counter circuit. Higher clock frequencies can allow the counter to count at a faster rate, but it also introduces the risk of potential glitches and timing issues.