Sampled transfers to system-level proof

AXI, APB, AHB & Ready/Valid Verification

Learn how to verify ready/valid flow control, APB, AHB and AXI with precise handshake rules, protocol assertions, transaction scoreboards and coverage.

Follow each transaction from a sampled handshake through wait states, bursts, IDs, responses and end-to-end checking—then practice the exact failure modes interviewers use.

32 direct practice links3 chaptersReviewed July 2026

Protocol analyzerCount accepted edges, not busy-looking cycles.

Sampled edge

C0 · offerVALID=1 · READY=0

Beat A is visible, but no transfer occurs at this sampled edge.

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Chapter 1 · Transfer contracts

Ready/valid is simple only when every edge is counted correctly.

A source offers one beat with VALID, a destination accepts it with READY, and state changes only when both are sampled high on the same rising edge.

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Chapter 1 · Transfer contracts

APB verification is a phase machine, not just a PREADY check.

Every transfer uses a SETUP cycle followed by one or more ACCESS cycles, with request information frozen while a peripheral extends the transfer.

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Chapter 1 · Transfer contracts

AHB pipelines addresses and data, so the monitor must remember history.

The address and control phase of transfer N+1 can overlap the data phase of transfer N; HREADY determines when the current data phase and the next address acceptance may advance.

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Chapter 2 · AXI transfers

AXI verification must preserve channel independence and transaction dependencies.

AXI separates read address, read data, write address, write data and write response traffic so each channel can stall independently while the transaction remains coherent.

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Chapter 2 · AXI transfers

A burst is one request with a beat-by-beat proof obligation.

At address acceptance, the verifier can derive beat count, bytes per beat, legal addresses, byte lanes, terminal beat and 4 KiB legality before any data arrives.

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Chapter 3 · Ordering & closure

AXI scoreboards need per-ID order, not one global FIFO.

AXI permits useful concurrency and response reordering while preserving required order within the applicable ID and destination relationship.

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Chapter 3 · Ordering & closure

Protocol closure needs assertions, transactions, scoreboards and coverage.

No single checker proves a bus. Local safety properties find cycle-accurate violations, while monitors, predictors, scoreboards, coverage and progress tracking prove the complete transaction lifecycle.

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The reasoning path

One transaction · four proof boundaries

Follow acceptance before you reason about completion.

A protocol transaction becomes trustworthy only when the verifier can connect the sampled signal event to reconstructed state, legal association, and an end-to-end result.

01Sample
Identify the exact edge that accepts work.
02Reconstruct
Retain phases, beats, IDs, and waits without inventing events.
03Associate
Reconnect independent channels only through legal dependencies.
04Close
Prove data, ordering, progress, reset, and zero outstanding work.

Standards and primary references

Check the contract at its source.

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