Keypad encoder in HDL scanning: After a key is released, the ring counter resumes its normal scanning sequence to poll rows/columns for the next keypress. Judge this behavior.

Introduction / Context:
Matrix keypads are commonly scanned by cycling drive lines via a ring counter while sampling sense lines. When a key is pressed, the scan halts long enough to capture and debounce the key code. Once the key is released, the system must resume scanning to detect subsequent keypresses.

Given Data / Assumptions:

• The keypad is arranged in rows and columns with pull-ups or pull-downs as appropriate.
• A ring counter steps through drive lines to excite one row/column at a time.
• HDL logic freezes or latches when a valid key is detected, then requires release to continue scanning.

Concept / Approach:
The scanning process is an FSM (finite state machine) with states such as IDLE, SCAN, DETECT, DEBOUNCE, LATCH, and RELEASE. A ring counter provides a one-hot drive pattern. On press, the encoder captures the key code; on release (no active row/column short), the FSM returns to SCAN, and the ring counter resumes sequencing.

Step-by-Step Solution:
Ring counter advances continuously in SCAN.Keypress detected → FSM halts advance and debounces.Key code is encoded and presented to output logic.On release signal (no closure), FSM re-enters SCAN → ring counter resumes stepping.

Verification / Alternative check:
Waveform simulation shows one-hot ring counter progression stopping during a valid press and resuming after the release event clears.

Why Other Options Are Wrong:
Matrix size does not fundamentally change the resume behavior. Asynchronous clocks are not required; synchronous designs work well. Pull-up values affect signal integrity but not the state-machine rule to resume.

Common Pitfalls:
Failing to implement a “key release” detection, causing lockup; inadequate debounce that resumes scanning too early or too late.

Final Answer:
Correct