ADC Synchronization: Multi-Card Timebase & Trigger Alignment
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Synchronization is not “sharing a clock” — it is making skew, drift, and repeatability measurable and repeatable across boards. This page turns multi-card alignment into a budget + bring-up recipe + verification tests so ownership is clear and results stay deterministic after reboots and temperature changes.
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What this page solves
Goal: determine in 30 seconds whether the issue is a synchronization problem, and obtain a repeatable architecture + bring-up + verification deliverable.
Typical symptoms (observable and falsifiable)
- Stitch mismatch: waveforms from Card A/B/C do not merge cleanly; seam steps, echoes, or periodic discontinuities appear.
- Coherence loss over time: alignment looks correct at start, then relative phase slowly shifts during long capture (hours/minutes scale).
- Trigger-to-sample mismatch: the same trigger event lands on different sample indices across cards; event markers disagree.
- Non-repeatable after reboot: a reset/re-lock changes relative alignment; calibration or stitching breaks after power cycle.
Synchronization failures are rarely fixed by “sharing a clock” alone. A working system requires three controlled objects end-to-end: Clock (timebase), Align reference (common start state), and Trigger (event timing) — plus proof by measurement.
Deliverables provided on this page (project-ready)
- Architecture chooser: choose star/tree/daisy and select which signals must be distributed (Clock / SYSREF-or-FSYNC / Trigger) based on the alignment target.
- Budget template: allocate Skew, Drift, Repeatability to owners (fanout, routing, connector/cable, receiver, digital path).
- Bring-up recipe: a fixed order (lock → align → verify → log) to make alignment reproducible across boots and re-locks.
- Acceptance test plan: measurable pass/fail criteria + required logs (P50/P90/P99 statistics, conditions, and evidence captures).
60-second self-check (Yes/No)
Q1: Does the system require multi-card stitching, coherent combining, or phase-sensitive processing? If Yes → sample/frame coherence matters.
Q2: Does a reboot or link re-lock change the alignment outcome? If Yes → repeatability and deterministic latency are not guaranteed.
Q3: Does the alignment drift with temperature or long capture time? If Yes → drift budget + thermal symmetry must be validated.
Q4: Are triggers shared but sample indices disagree across cards? If Yes → trigger distribution is not equivalent to sample alignment.
Scope guardrail: this page focuses on alignment architecture, repeatable bring-up, and verification. Jitter-to-SNR math, SERDES eye tuning, and protocol register walkthroughs are intentionally out of scope here to avoid cross-page overlap.
Definition: synchronization targets (measurable and verifiable)
“Synchronization” is not a single property. It is a set of acceptance targets that must hold simultaneously for Clock, Align reference, and Trigger. This section defines the three core metrics and the minimum evidence required to claim pass/fail.
Required output format: (Budget) + (Measurement method) + (Conditions) + (P50/P90/P99) + (Logs).
The three acceptance metrics (each must have pass/fail)
1) Static skew (fixed offset)
- Definition: channel-to-channel time offset under steady-state conditions.
- Units: ps/ns or samples (use samples when the system consumes sample indices; use time when mixing sample rates).
- How to measure: common stimulus + cross-correlation; or common tone phase difference converted to time; or per-card marker capture to sample index.
- Pass/Fail template: P99(|Δt|) ≤ Skew_budget under defined conditions.
2) Drift (relative change over time/temperature)
- Definition: change in relative alignment after initial lock/alignment.
- Two required windows: long capture (time window) and temperature step (thermal window).
- How to measure: repeated correlation/phase checks at fixed intervals; report slope and worst-case excursion over the window.
- Pass/Fail template: max(|Δt(t) − Δt(t0)|) ≤ Drift_budget over the specified time + temperature profile.
3) Repeatability (reboot / re-lock return-to-state)
- Definition: alignment distribution after reset, power-cycle, or re-lock (the system must return to the same alignment state).
- Why it is critical: poor repeatability invalidates “one-time calibration,” stitching offsets, and long-term comparability.
- How to measure: N cycles (power cycle or forced re-lock) → measure skew each cycle → report histogram statistics.
- Pass/Fail template: P99(|Δt| across cycles) ≤ Repeat_budget with a fixed bring-up order.
Minimum evidence required (to avoid “seems aligned”)
- Conditions: temperature points, duration, airflow state, and the exact bring-up order used.
- Logs: PLL/lock state, align state (armed/latched), trigger marker captures, link-ready state, and any re-sync events.
- Statistics: P50/P90/P99 for each metric; report worst-case and cycle count N for repeatability.
Requirement spec: decide “what must align”
Synchronization architecture is dictated by the alignment target. Lock the target first, then design the clock/align/trigger distribution to meet it with measurable pass/fail.
Step 1 — Pick exactly one target type
A) Sample-level phase coherence
- What must align: the sampling instant across cards/channels, continuously (phase-coherent over time).
- What it enables: coherent combining, beamforming, multi-channel phase measurements, stitched wide-aperture capture.
- What it forbids: nondeterministic latency (elastic buffers that change depth across boots) and uncontrolled re-lock phase states.
- Non-negotiables: shared timebase + deterministic alignment reference + deterministic data path.
B) Frame-level alignment
- What must align: frame or cycle boundaries (start-of-frame sample index is identical across cards).
- What it enables: multi-phase control sampling, periodic processing windows, deterministic segmentation.
- What can vary: phase inside the frame may be calibrated, as long as boundary and index mapping are deterministic.
- Non-negotiables: a common frame marker (FSYNC/SYSREF/epoch) + deterministic mapping to sample indices.
C) Event-level trigger coherence
- What must align: the same event is captured at the same time (or time-tag) across cards, within a defined tolerance.
- What it enables: time-correlated measurement, distributed capture, episodic acquisition.
- What is optional: continuous phase coherence is not required; periodic re-sync is often acceptable.
- Non-negotiables: trigger distribution + a shared time reference (or a well-defined timestamp conversion).
Step 2 — Convert system constraints into hard requirements
Step 3 — Declare the spec in one paragraph (freeze scope)
Target type is Sample / Frame / Event. The acceptance metrics are Skew, Drift, and Repeatability, reported in time and samples. The topology spans [distance/topology] and [single/dual chassis]. The thermal envelope is [range/profile]. Re-sync is [allowed/not allowed] with [period/window]. Link determinism is [required/not required]. Verification must provide P50/P90/P99 statistics and the defined log bundle.
System timing model: where uncertainty enters
A synchronization problem becomes solvable only after the end-to-end timing chain is decomposed into segments. Each segment must be assigned an owner and mapped to one dominant uncertainty type: Mismatch (static skew), Repeatability (re-lock spread), Routing (drift), or Determinism (digital latency states).
Rule of thumb: fixed offset → investigate mismatch; time-dependent shift → investigate drift; reboot-dependent shift → investigate repeatability/determinism.
Segment map (assign responsibility)
1) Ref → Cleaner/PLL
- Primary risk: Repeatability (power-up phase state), Drift (frequency/phase wander across temperature).
- Typical failure signature: alignment changes after re-lock even if routing is unchanged.
- Evidence: lock state logs + repeated lock cycles with measured skew distribution.
2) Fanout → Board ingress
- Primary risk: Mismatch (channel delay differences), Routing (cable/backplane thermal drift).
- Typical failure signature: a stable but non-zero offset that varies with cable swaps or temperature.
- Evidence: edge-to-edge measurements at the far nodes + drift checks over the declared window.
3) Card receiver → ADC sampling instant
- Primary risk: Repeatability (local PLL/CDR state), Mismatch (fixed internal delays).
- Typical failure signature: ingress edges look aligned, but correlation/phase at ADC outputs is not.
- Evidence: common stimulus phase/correlation check translated into time/samples.
4) ADC → FPGA capture → Data marker/time-tag
- Primary risk: Determinism (FIFO depth changes, CDC timing), Repeatability (training/align state machines).
- Typical failure signature: alignment differs across boots even with identical analog timing and routing.
- Evidence: marker index consistency + FIFO/align state logs across N cycles.
Turn the chain into budgets (time + samples)
- Total static skew = Σ(mismatch terms) across fanout, cables/backplane, routing, receiver, and fixed digital offsets.
- Total drift = worst-case excursion of relative alignment over the specified time + temperature profile.
- Total repeatability spread = distribution of alignment states across reboot/re-lock/re-train cycles (must be reported as P99).
- Samples conversion: samples = time × fs (report both units when the consumer is sample index based).
Minimum measurement loop (do not skip)
- Lock → align → capture in a fixed bring-up order; record lock/alignment states and any training counters.
- Measure skew at the output domain that matches the target (stimulus correlation/phase for sample-level; marker index for frame/event).
- Measure drift by repeating the same check over time and across the temperature profile; report worst-case excursion.
- Measure repeatability using N cold/warm boots and forced re-locks; report a histogram and P50/P90/P99.
Timebase generation: choose the master reference
A master reference is not selected for “cleanliness” alone. It must keep the synchronization state controllable through boot, re-lock, reference loss, and redundancy switching so that Skew, Drift, and Repeatability remain verifiable.
What the reference is responsible for (synchronization view)
- Provide a distributable timebase that can be converted into clock + alignment signals for all nodes.
- Keep phase behavior testable across power cycles and re-lock events (repeatability is a requirement, not a hope).
- Define failure modes for reference loss and recovery (holdover entry/exit must be observable and policy-driven).
Key reference fields (only what affects synchronization)
Redundancy and switching (what must be verified)
Single reference
- Benefit: one state machine; repeatability is easier to control and test.
- Risk: reference loss forces a mode transition (holdover or re-sync).
- Verification: reference-loss injection must be part of acceptance testing.
Redundant reference (main/backup)
- Benefit: improves uptime.
- New risk: switching can break phase continuity; “still running” is not equal to “still aligned.”
- Verification: after a switch, alignment must remain within repeatability limits or a controlled re-sync policy must trigger with a clear epoch marker.
Holdover is a mode, not a hope
When the reference is lost, the system must enter a declared holdover mode with observable state. The spec must define a holdover window and a re-sync policy for exit. Any data captured across a mode boundary must be epoch-marked to prevent silent stitching failures.
Distribution topology: star vs daisy vs tree
Topology determines how skew can be controlled, how the system scales, and how quickly root causes can be isolated. Choose a topology that matches the target type and the verification plan.
Compare using the same three lenses
- Skew control: can delay mismatch be budgeted and corrected at the endpoints?
- Scale: does adding nodes grow the budget linearly and remain testable?
- Debug: can failures be localized without dismantling the system?
Star
- Skew control: best; each node has a directly budgeted path from the center.
- Scale: limited by fanout resources and cabling/ports.
- Debug: strongest isolation; a failing branch is contained.
Daisy chain
- Skew control: weakest at scale; delay accumulates and end nodes inherit all upstream variability.
- Scale: wiring-efficient, but the last node is hardest to keep within budget.
- Debug: cascading failures; middle nodes are critical risk points.
Tree
- Skew control: strong if budgets are defined per level (trunk vs leaf).
- Scale: balanced; grows by branches while keeping measurement points structured.
- Debug: good when each tier has observability; failures localize by tier.
Connectors and distance are repeatability risk points
Any pluggable point can change delay and drift characteristics across cycles. Place connectors away from the highest-sensitivity segments, and require reboot/re-plug repeatability testing as part of acceptance, not as an afterthought.
Alignment reference: SYSREF / FSYNC / frame markers
A shared clock advances time, but an alignment reference defines the zero point. It collapses random alignment states into a deterministic boundary that can be verified and repeated.
Why an alignment reference is needed
- Defines a boundary: phase zero, frame start, or epoch marker shared by all nodes.
- Forces a discrete state: internal alignment logic converges to a repeatable latch point instead of drifting across random boot/training states.
- Makes repeatability measurable: the same bring-up sequence should land on the same latched index/phase distribution.
Alignment strategies (single-shot vs periodic)
Single-shot alignment
- Goal: lock the zero point once and keep data continuous.
- Works when: drift remains inside the acceptance window for the entire capture interval.
- Acceptance focus: reboot/re-lock repeatability (P99) and stable mapping to sample indices.
- Failure mode: slow drift accumulates and silently breaks stitching if not monitored.
Periodic alignment
- Goal: re-anchor the boundary to control drift across long time or harsh temperature profiles.
- Works when: the system can tolerate epoch boundaries or aligns only inside a declared window.
- Acceptance focus: epoch markers must be explicit; alignment events must not be silent.
- Failure mode: periodic events can inject discontinuities unless windows and markers are enforced.
Alignment window and failure handling
- Window open: all nodes are ready to observe the reference and latch a common boundary.
- Latch state: the alignment state machine locks an index/phase and freezes the state.
- Window close: a timeout ends the attempt and activates the defined failure policy.
- Failure policy: fail-fast (data invalid), degrade (mode switch with marking), or re-try (bounded retries with logs).
Minimum acceptance evidence (protocol-agnostic)
- Repeatability: N boots/re-locks produce a P99 distribution of latched phase/index inside the requirement.
- Deterministic completion: align_done occurs within a declared time range; align_fail provides a reason code.
- Epoch correctness: periodic alignment produces explicit epoch/frame markers so data stitching is policy-driven.
Trigger & gating: coherent start/stop events
A trigger is an event system, not just a wire. Coherent triggering requires controlled arrival skew, bounded edge uncertainty, and consistent gate width, with measurable evidence per board.
Acceptance metrics (how to claim “coherent”)
Trigger coherence does not guarantee sample-phase coherence
A coherent trigger aligns an event boundary. It does not guarantee that sampling instants are phase-aligned across boards. Sample-level coherence still requires a shared timebase and a deterministic alignment reference.
Distribution and measurement points
- Star trigger tree: simplifies delay matching and keeps skew budget visible at the endpoints.
- Standardize a measurement point: define where the system “consumes” the event (board ingress vs FPGA capture are not equivalent).
- Convert the event into data: produce an event index or timestamp per board for direct comparison.
Minimum evidence bundle
- Edge capture logs: per-board arrival timestamp or sample index, plus gate start/stop markers.
- Statistics: P50/P90/P99 of arrival skew and window length differences.
- Traceability: each event is tied to a unique event index for cross-board correlation.
Deterministic latency: keep digital paths repeatable
Clocks can be aligned while data still refuses to stitch. The root cause is variable digital latency. Synchronization requires a declared alignment point and a repeatable digital state across boot, reset, and re-lock.
Define the alignment point first
- Sample index: the strict endpoint for sample-level coherence (most sensitive to variable latency).
- Frame marker: the boundary for frame-aligned systems where phase inside a frame may be secondary.
- Event index / time tag: the endpoint for coherent triggering and timestamped acquisition.
Where non-determinism comes from (symptoms and acceptance impact)
Elastic buffers and multi-stage pipelines
- Symptom: the same marker lands at different indices run-to-run.
- Acceptance risk: repeatability fails even if static skew looks fine.
- Required observability: buffer level, slip/realign counters, alignment status.
Reset and align sequencing differences
- Symptom: a late-ready node shifts the effective latch point, changing the end-to-end delay.
- Acceptance risk: alignment becomes dependent on timing accidents.
- Required observability: align window open/close times, align_done timing, reason codes.
Lane deskew and clock-domain crossing (CDC)
- Symptom: sample boundaries move after retrain or re-lock while the link stays “up.”
- Acceptance risk: cross-board delta shifts across boots or temperature changes.
- Required observability: deskew lock, FIFO pointers, retrain/realign events tied to epochs.
Synchronization controls (digital determinism)
- Fence the variable latency zone: declare which blocks are allowed to vary and keep that variation bounded relative to the alignment point.
- Standardize a reset + align state machine: clock stable → link stable → align window → latch → data valid, with bounded retries and explicit epoch changes.
- Prove repeatability with a known marker: use a training sequence or marker to validate that each run lands on the same index distribution.
Minimum acceptance claims (protocol-agnostic)
- Run-to-run index repeatability: the marker’s latched sample/frame index stays within the requirement distribution (report P99).
- Cross-board delta repeatability: board-to-board index differences remain bounded across reboots and relocks.
- Mode boundary traceability: retrain/reset/realign events always produce an epoch marker and a log entry.
Skew & drift budgeting: allocate error to owners
Engineering-grade synchronization turns “alignment” into a budget sheet. Each segment must have a measurement method, an acceptance threshold, and a clear owner who can change it.
Budget template: static skew (who owns each contributor)
Budget template: drift (windowed and testable)
Bring-up sequence: make alignment reproducible
A stable clock is not enough. Reproducible alignment requires a fixed state machine: each step must pass a gate before the next step is allowed, and every recovery must be traceable by logs and epochs.
Recommended sequence (do not skip steps)
Why skipping steps breaks repeatability
- Skipping Ref stable: warm-up drift appears as “mysterious” alignment change after a seemingly good bring-up.
- Skipping Link ready: deskew/CDC/buffer states can move after alignment, shifting sample boundaries.
- Skipping Align ref: a trigger can align events but cannot guarantee a deterministic sample or frame boundary.
Re-sync policy (periodic re-align vs full-chain reset)
Periodic re-align is allowed only when
- Epoch markers exist: boundary changes are explicit and policy-driven (no silent switching).
- Windows exist: re-align runs inside declared windows (frame gaps, gated intervals, or safe epochs).
- Fast verification exists: a quick marker/trigger check validates the new state immediately.
Full-chain reset is required when
- PLL unlock / holdover uncertainty: phase continuity cannot be claimed.
- Link retrain or deskew changes: sample boundary may move (variable latency zone changed).
- Trigger out-of-window persists: bounded retries fail to restore acceptance.
- Repeatability fails: run-to-run distributions exceed thresholds or become multi-modal.
Minimal logs to make bring-up auditable
- Timestamps: ref_stable, pll_lock, link_ready, align_done, trigger_ok.
- State: pll_lock, holdover, link_up, retrain_count, deskew_status, fifo_ptr, slip_count.
- Markers: epoch_id, align_fail_reason, trigger_skew_stats, gate_width_stats.
- Versions: firmware/bitstream/config snapshot ID for reproducibility.
Verification methods: measure skew, drift, repeatability
Verification must produce a report that survives hardware swaps and firmware updates. Each test case needs a fixed fixture, a defined measurement point, a statistic (P99), and a pass/fail threshold.
Test case TC0: readiness (make results meaningful)
- Claim: the system is in a measurable state before skew/drift tests start.
- Checks: pll_lock=1, link_up=1, retrain/slip counters bounded, epoch explicit.
- Fail action: return to the bring-up gates until TC0 passes.
Test case TC1: static skew (two practical methods)
Method A: cross-correlation
- Fixture: generator → splitter → A/B/C inputs.
- Process: correlate waveforms to find Δsamples; convert to time.
- Acceptance: report P50/P90/P99 and a board-to-board delta matrix.
Method B: sine phase difference
- Fixture: same generator/splitter setup.
- Process: measure Δφ and convert to Δt using the stimulus frequency.
- Acceptance: use P99; verify results at multiple frequencies if needed.
Test case TC2: drift (windowed and stimulus-driven)
- Stimulus: temperature chamber, hot-air, airflow change, or load step that creates thermal gradients.
- Capture: measure skew in windows (e.g., repeated short captures) over long time.
- Acceptance: drift per window stays under threshold; log epoch changes and retrain events.
Test case TC3: repeatability (N reboots / relocks)
- Procedure: repeat bring-up N times and measure skew each time at the same alignment point.
- Statistics: min/mean/max plus P99; plot a histogram of run-to-run deltas.
- Interpretation: multi-modal histograms indicate multiple discrete digital states (non-determinism).
Report format: synchronization acceptance sheet (copy template)
Troubleshooting: isolate ownership quickly
Fixing synchronization starts with fast ownership isolation. Each branch below uses a minimum test to push the issue into one segment (PCB / HW / FW / SYS) before deeper debugging begins.
Tree A: large skew but stable (fixed delay)
- Symptom: Δt is large, but barely changes within a time/temperature window.
- Likely causes: routing mismatch, fanout channel mismatch, ingress capture differences.
- Minimum tests: swap cable/port paths; compare results against the same stimulus and measurement point.
- Ownership: follows cable/port → SYS/HW; follows board location → PCB; follows capture settings → HW/FW.
Tree B: drift is obvious (time/temperature sensitivity)
- Symptom: Δt grows or wanders with time, temperature, airflow, or load.
- Likely causes: thermal gradient, PLL/holdover behavior, supply sensitivity.
- Minimum tests: apply a controlled heat/airflow stimulus; observe windowed drift while tracking epochs and relock events.
- Ownership: tied to airflow/layout → SYS/PCB; tied to lock/holdover → HW; tied to rail steps → HW/SYS.
Tree C: non-repeatable across boots/relocks (digital state)
- Symptom: alignment looks good in one run, but shifts after reboot/relock/reset.
- Likely causes: variable latency zones (buffers/deskew/CDC), unstable align sequencing, silent retrain events.
- Minimum tests: run N bring-ups with the same recipe; build a histogram of marker index deltas; check for multi-modal states.
- Ownership: multi-modal index states → FW; retrain/deskew involvement → FW/HW; step ordering dependence → FW/SYS.
Fast isolation rules (minimum tests that save time)
- Swap test: if the error follows a cable/port, the cause lives in the swapped segment.
- Window test: stable in a window implies fixed delay; changing across windows implies drift.
- Epoch test: any silent state change without an epoch marker is a design bug (traceability failure).
- Histogram test: multi-modal distributions indicate multiple discrete digital states.
Engineering checklist: design, bring-up, acceptance
This one-page checklist compresses the full synchronization workflow into four phases. Each item is written as an action that can be checked off during a real project.
Phase checklist (copy and paste)
Spec
- Pick target type: sample / frame / event.
- Define pass/fail thresholds (P99).
- Declare temperature and airflow envelope.
- Decide re-sync policy and allowed windows.
Design
- Choose topology: star / tree / daisy.
- Declare alignment point (index/marker).
- Fence variable latency zones.
- Build skew + drift budget sheets with owners.
Bring-up
- Run gated bring-up (no skipping).
- Log lock/link/align/epoch fields.
- Define bounded retries and recovery.
- Capture calibration snapshot after verify.
Verify
- TC0 readiness before measurements.
- TC1 static skew with P99 matrix.
- TC2 drift with windowed stimulus.
- TC3 repeatability with histogram check.
Applications: why synchronization must be done this way
Each application below is written as a three-line capsule: requirement → target type → common architecture. The focus is on failure modes and acceptance, not protocol fields.
Multi-card DAQ (wideband stitching)
Requirement: stitched waveforms must not jump at boundaries.
Target type: Frame-level (upgrade to Sample-level for coherent analysis).
Common architecture: shared master ref + star/tree distribution + explicit align marker + deterministic data alignment point.
- Stitch artifacts usually come from sample-index shifts, not random noise.
- Acceptance must track marker index deltas (P99), not only average skew.
Phased array / beamforming (phase coherent)
Requirement: relative phase must remain coherent across channels.
Target type: Sample-level phase coherence.
Common architecture: low-drift master ref + star distribution + align marker policy (single-shot/periodic) + epoch-based traceability.
- Trigger coherence alone aligns events, not sample phase.
- Drift is the silent killer; acceptance must include long-window statistics.
Multi-phase power measurement (phase & gating)
Requirement: phase relationships must be consistent for PF, harmonics, and transient analysis.
Target type: Frame-level (upgrade to Sample-level for transient debug).
Common architecture: synchronized sampling + trigger tree with bounded skew + explicit alignment point at sample index or frame marker.
- Gate width mismatch creates hidden measurement-window offsets.
- Acceptance must define a shared measurement point and a P99 phase/skew limit.
Distributed monitoring (event-first)
Requirement: the same event must align in time-tags for correlation and root cause analysis.
Target type: Event-level trigger coherence.
Common architecture: trigger/marker distribution + epoch policy + reproducible bring-up + explicit event index/time-tag definition.
- Event alignment can be strong without paying for sample-level coherence.
- Acceptance must include repeatability after reboots and relocks.
IC selection logic: fields → risk mapping → RFQ template
Synchronization failures are often procurement failures: the wrong questions were asked. This section turns synchronization requirements into device fields, maps missing fields to system risks, and provides a copy-ready RFQ template.
A) Parameter fields checklist (with example part numbers)
B) Risk mapping: missing fields → system failures
C) RFQ template (copy-ready)
Paste the following into an email to vendors or distributors:
Subject: RFQ – Multi-card synchronization (clock + align + trigger) 1) System targets (pass/fail) - Static skew (P99): ________ (ps/ns or samples) - Drift (windowed): ________ (samples/hour or ppm/°C equivalent) - Repeatability (N reboots/relocks, P99): ________ - Target type: Sample / Frame / Event - Deterministic latency required: Yes / No - Allowed periodic re-align: Yes / No (allowed windows: ________) 2) Topology and environment - Topology: Star / Tree / Daisy - Cable/connector count per path: ________ - Cross-chassis: Yes / No Distance: ________ - Temperature range / airflow constraints: ________ 3) Device questions (must answer with datasheet references) A) Master reference / oscillator - Warm-up behavior, stability, and any holdover statement: - Recommended distribution conditions: B) PLL / jitter cleaner - Lock time, lock status pins/flags, loss-of-lock behavior: - Phase continuity policy on relock: - Align marker support (SYSREF/FSYNC/marker generation and routing): C) Fanout / buffer - Output-to-output skew specification: - Additive jitter specification: - Channel enable behavior and power-up defaults: D) Trigger / gating distribution - Propagation consistency and skew: - Enable/gate behavior and deterministic timing: E) Receiver / input conditioning (if long lines) - Input threshold requirements, termination guidance: 4) Verification artifacts requested - Provide a recommended bring-up sequence (gated steps). - Provide how to verify skew/drift/repeatability (minimum tests). - Provide a list of example parts that match the above constraints, with availability lead times.
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FAQ: synchronization, deterministic latency, and verification
Each answer uses the same data-structured format: Decision → Acceptance → Minimum test → Common traps → Next action.
