Generating equally spaced timing pulses — Which counter/sequencer topology is commonly used to create a sequence of evenly spaced timing outputs with simple decoding?

Introduction:
Timing generators often need multiple nonoverlapping, evenly spaced phase signals. Certain counter topologies simplify decoding and ensure uniform spacing without complex logic.

Given Data / Assumptions:

• Goal: produce a set of sequential timing pulses, one per clock step.
• Low logic complexity desired for decoding.
• Consistent duty cycle and spacing preferred.

Concept / Approach:

A Johnson counter (twisted ring) feeds the inverted output of the last flip-flop back to the first. It cycles through 2N unique states using N flip-flops, providing evenly spaced, easily decoded outputs. Simple gating can extract narrow pulses or phase signals with minimal logic compared to binary counters.

Step-by-Step Solution:

Verification / Alternative check:

Design texts show that, for the same number of flip-flops, Johnson counters need fewer gates to obtain nonoverlapping phases than binary counters, and are widely used in timing sequencers and DAC timing logic.

Why Other Options Are Wrong:

• Shift register sequencer / ring: Workable, but Johnson offers 2N states and easier decoding for equal spacing.
• Binary: Requires more complex decoding to obtain equal spacing and one-hot pulses.
• Clock: A clock alone is a single pulse train, not a sequencer topology.

Common Pitfalls:

• Mistaking simple ring for Johnson; the twisted feedback differentiates them.
• Ignoring reset/initialization to a valid Johnson state.

Final Answer:

johnson