Shift-register counters and topology Shift-register-based counters depend on ________, meaning the output of the last flip-flop is routed back to the first flip-flop in a defined manner.

Introduction / Context:
Some counters are built from shift registers rather than from dedicated counter structures. Examples include ring counters and Johnson (twisted-ring) counters. Their operation depends on recirculating data so that a pattern cycles through the register stages.

Given Data / Assumptions:

• A shift register is composed of cascaded flip-flops clocked together.
• To create a sequence, the end output is routed back to the input in some form.
• The recirculation may be direct or inverted depending on the desired sequence.

Concept / Approach:
The general term for routing an output back into an earlier point in the circuit is “feedback.” Ring counters use direct feedback of a single 1 (or 0), while Johnson counters use inverted feedback to generate 2n distinct states from n stages. Without feedback, data would simply shift out and be lost rather than forming a repeating sequence.

Step-by-Step Solution:
Identify architecture: shift-register stages clocked in parallel.Recognize need for a closed loop to repeat a pattern.Name the technique: feedback.

Verification / Alternative check:
State sequences for ring and Johnson counters clearly show the role of the looped connection. Timing diagrams confirm that after n or 2n steps the initial pattern reappears.

Why Other Options Are Wrong:
“MOD” refers to modulus, not topology. “Strobing” is a glitch-masking technique. “Switchbacks” is not standard terminology.

Common Pitfalls:
Mixing up direct vs. inverted feedback; neglecting initialization so that the register does not enter a valid sequence.

Final Answer:
feedback