BAS-506 Visual Aid Library
Figure-use rule
Each figure is an orientation and reasoning aid, not a project drawing. Learners must pair it with the current sequence, point list, wiring/piping documents, manufacturer instructions, and as-found evidence.
Normal-rule anchor
A protocol name does not define cable, routing, data meaning, writable authority, or physical result; each layer and contract must be proved.
Case overlay
A temperature reaches a supervisor through a legacy controller, serial gateway, IP network, and BACnet object, but no one owns the scale conversion.
Calculation/evidence callout: Count boundaries and dependencies, map addresses and transforms, and calculate end-to-end update and command-to-proof time.
Normal-rule anchor
Object presence does not guarantee optional properties, services, writable behavior, units, priority support, or conformance; verify product claims and observed behavior.
Case overlay
A tool reads Present_Value but the object is out of service, units are wrong, and a write at priority 8 never reaches the equipment.
Calculation/evidence callout: Reconcile object and property coverage, active priorities, COV/timing, status, and command-to-proof response.
Normal-rule anchor
BACnet/IP, BACnet/SC, and IT network reachability are related but distinct; allowed traffic must be explicit and application behavior must be proved.
Case overlay
Devices discover locally but not across subnets, a foreign-device entry expires, and a proposed BACnet/SC hub has no certificate lifecycle owner.
Calculation/evidence callout: Calculate subnet and route coverage, BDT/FDR entries and TTL, packet/latency behavior, certificate lead time, and failure-domain impact.
Normal-rule anchor
The token cannot fix the wire; screen discovery never replaces approved cable/topology, polarity, reference, termination, loading, grounding, and physical inspection.
Case overlay
A trunk has long stubs, mixed baud, duplicate MAC, missing end termination, and one device that appears only after power cycling.
Calculation/evidence callout: Calculate segment/device loading, token rotation estimate, baud-related transfer time, error concentration, and before/after response.
Normal-rule anchor
A plausible number is not valid evidence until the complete register contract and physical/process comparison are proved.
Case overlay
A meter value is 65,536 times too large, two devices share a serial address, and the gateway retries an unsupported function continuously.
Calculation/evidence callout: Convert addresses and raw values, test endian combinations, calculate poll-cycle/load and timeout/retry behavior, and compare engineering plausibility.
Normal-rule anchor
LonWorks connections behave like virtual wires; replacing or resetting a node without preserving identity, bindings, domain, configuration, and application can disconnect the system.
Case overlay
A replacement node powers up but its output network variables no longer reach three bound controllers.
Calculation/evidence callout: Reconcile node and domain identity, binding counts, update/heartbeat timing, SNVT units/scaling, channel load, and missing-variable coverage.
Normal-rule anchor
Legacy experience is not permission to experiment; preserve rare documentation, tools, licensing, media, backups, cables, and known-good hardware while protecting customer data.
Case overlay
A Teletrol controller serves occupied equipment, its last backup is unknown, and a replacement gateway claims generic serial support without a verified point contract.
Calculation/evidence callout: Count assets and unsupported dependencies, score documentation/backup coverage, calculate polling and outage risk, and estimate migration verification effort.
Normal-rule anchor
A gateway is an application with hidden state and blast radius; every transform and failure mode requires source, destination, ownership, test, and rollback.
Case overlay
A gateway continues serving cached normal values after its source bus fails and accepts writes without returning equipment proof.
Calculation/evidence callout: Calculate end-to-end latency, cache/stale thresholds, poll/write load, scale and enum transforms, command/proof timeout, and affected-point blast radius.
Normal-rule anchor
Do not modernize by erasing the old truth; baseline, shadow comparison, owner authority, safety/critical interfaces, support window, backup, abort, and rollback precede cutover.
Case overlay
A hospital wing depends on a legacy interface that also reports smoke-control status, and the proposed gateway replacement changes network behavior.
Calculation/evidence callout: Calculate point and mode coverage, parallel comparison error, outage and rollback time, recovery objective, risk/exception counts, and acceptance pass rate.
Normal-rule anchor
Integration is complete only when required reads/writes, quality, timing, alarms/trends/schedules, physical response, failure/fallback, recovery, security, as-builts, and ownership all pass.
Case overlay
A mixed-protocol lab passes normal reads but fails after gateway restart and leaves one command active at an undocumented priority.
Calculation/evidence callout: Reconcile requirements/tests/issues/retests, calculate availability/latency/RPO/RTO, account for every target and temporary state, and quantify unresolved risk.