Terminal count of a decade (MOD-10) binary counter In a typical binary decade counter that counts 0–9 and then resets, what is the terminal count pattern just before recycling?

Introduction / Context:
The term “terminal count” refers to the last valid state in the counting sequence before the counter recycles to 0. For a MOD-10 (decade) counter implemented with binary flip-flops and reset decode logic, understanding which pattern is the terminal count avoids confusion with the reset-detect pattern itself (which is not a state in the sequence).

Given Data / Assumptions:

• Counter counts 0000 (0) up to 1001 (9).
• Upon reaching 1010 (10), reset logic forces 0000.
• Binary outputs are active-high and standard order Q3..Q0.

Concept / Approach:

Enumerate valid states and identify the last one before reset occurs. In a binary decade, states 0000..1001 are valid; the detection of 1010 asserts reset. Thus, the terminal count is 1001 (decimal 9).

Step-by-Step Solution:

Verification / Alternative check:

Check typical 74xx90/92/160-series decades: documentation shows reset gates wired to detect 1010 (or equivalent), confirming 1001 is the terminal state.

Why Other Options Are Wrong:

0000 is the first state, not the last.

1010 is the reset-detect pattern and not part of the normal sequence.

1111 is unrelated to decade counting and appears in straight binary MOD-16 sequences, not in a decade counter.

Common Pitfalls:

Confusing “terminal count” with “reset code,” and assuming the counter actually enters 1010. Properly designed decades skip 1010 by resetting immediately.

Final Answer:

1001