Answer :
Final answer:
The decade counter is an example of a counter with a truncated modulus, as it resets after counting to a pre-defined number (9) despite having enough bits to count higher.
Explanation:
A counter with a truncated modulus is a counter that does not go through all the possible states of a certain number of bits before resetting. Among the options given, the decade counter exemplifies a truncated modulus counter. A decade counter, or BCD (Binary Coded Decimal) counter, typically counts from 0 to 9 (10 states) and then resets to 0, even if it has enough flip-flops to count higher (like up to 15 in 4 bits). This is because it is designed to represent each decimal digit with a binary number, and once it completes the count for the first decimal digit, it resets.
The operation of a binary pulse counter (BPC), such as described in Figure 4.3.3, typically involves multiple registers (or flip-flops). Each register can hold a binary value (0 or 1), and a pulse triggers a change in state from 0 to 1 or from 1 to 0. A counter such as this, with three registers, can count up to 2^3 (or 8) pulses. When a pulse is detected, it flips the rightmost register and continues flipping each consecutive register until it reaches one that flips from 0 to 1, which represents counting that pulse and stops the chain flipping for that pulse.
