Timing sequence generation – choosing the counter type Which counter is commonly used to generate a sequence of equally spaced timing pulses for control logic?

Introduction / Context:
Digital systems often need evenly spaced timing phases for sequencing (e.g., stepper processes, multiplexing). Choosing the right counter simplifies decoding and ensures nonoverlapping, uniform timing windows.

Given Data / Assumptions:

• We want multiple distinct timing pulses across a cycle.
• Uniform spacing and simple decoding are desired.

Concept / Approach:
A Johnson counter (twisted ring) produces 2n unique nonoverlapping states from n flip-flops. Its outputs are easy to decode into equally spaced phases, making it ideal for timing sequences. Ring counters are similar but yield only n states; binary counters require more decoding logic for equal-phase timing signals.

Step-by-Step Solution:

Verification / Alternative check:
Design handbooks recommend Johnson counters for timing/sequence generation because each output remains high for exactly n clocks in a 2n cycle, yielding clean, evenly spaced phases.

Why Other Options Are Wrong:

• Ring shift: Provides n states; fewer phases and less flexibility than Johnson for the same number of flip-flops.
• Clock: Not a counter type; it is the timing source itself.
• Binary: Requires additional decoding to achieve equally spaced, nonoverlapping pulses.

Common Pitfalls:

• Assuming a plain binary counter automatically provides equal, nonoverlapping timing phases without extra logic.

Final Answer:
Johnson