Industrial Protocols Glossary
Modbus, DNP3, OPC UA, MQTT, EtherNet/IP, PROFIBUS, HART, BACnet and other fieldbus and network protocols. 329 terms in this topic - each defined in plain English on its own page.
Every measurement on a dashboard traveled over one of these protocols. The definitions here cover the industrial application protocols and fieldbuses - register-based classics like Modbus, event-driven SCADA protocols like DNP3 and IEC 60870, modern information models like OPC UA and MQTT Sparkplug, and machine-level fieldbuses from PROFIBUS to EtherCAT. Understanding what each protocol models (registers, events, objects, or topics) matters more than memorizing frame formats; the deeper guides show working integrations end to end.
329 Terms
Why Can a Modbus Read Only Return 125 Registers at Once?
The 253-byte PDU ceiling that caps a read at 125 registers or 2000 coils, and why drivers split large maps.
Read → GlossaryWhat Is a 32-Bit Float in Modbus?
How a flow computer packs an IEEE-754 float into two 16-bit registers, why it reads as garbage, and how to verify it.
Read → GlossaryHow do you add a Modbus node to a live bus?
Assign a unique address on the bench, wire a short stub with correct polarity and no extra terminator, then verify nothing else broke.
Read → GlossaryWhat Is an OPC UA Application Instance Certificate and Trust List?
Per-application certificates and trust lists drive OPC UA mutual authentication, the rejected folder, and expiry risk.
Read → GlossaryWhat is AS-Interface (AS-i)?
The simplest fieldbus: one yellow flat cable carrying power and data to sensors, polled by a master and gatewayed to SCADA.
Read → GlossaryHow do you assign DNP3 event classes?
Rank points by urgency, map them to classes 1, 2, 3 with matching poll rates, and isolate noisy points from your alarms.
Read → GlossaryBACnet
The open building-automation protocol - objects, services, BACnet/IP vs MS/TP, and bringing facility data into SCADA.
Read → GlossaryBACnet Device Object
The mandatory object that names a device, lists all its objects, and declares its supported services and message limits.
Read → GlossaryWhy does BACnet discovery find nothing?
Who-Is broadcasts do not cross routers: check subnet, port, and firewalls, then the BBMD tables and foreign device registration.
Read → GlossaryBACnet Object and Property Model
How BACnet models devices as standard objects with typed properties, and why that self-describing structure eases integration.
Read → GlossaryBACnet Object Identifier
How the Object_Identifier fuses object type and instance, and why the Device object's identifier is the device's own address.
Read → GlossaryBACnet Present_Value Property
What Present_Value holds on inputs versus commandable outputs, and why writing it on an output goes through the priority array.
Read → GlossaryBalanced vs Unbalanced Transmission
IEC 60870-5-101 link modes, which serial topology each fits, and why 104 drops the distinction.
Read → GlossaryWhat Is Bell 202 Signaling in HART?
The 1970s telephone modem standard HART borrowed, which fixes its 1200 bps data rate and explains why polled HART is slow.
Read → GlossaryHow do you bisect an RS-485 bus?
Split the bus in half, terminate the working end, re-poll to find the bad half, and repeat until one node or segment remains.
Read → GlossaryBridge OPC UA Data to an MQTT Broker
Subscribe with deadbands, map nodes to stable topics, choose QoS, and handle both reconnects so the bridge is field-ready.
Read → GlossaryWhat Is a Modbus Broadcast Write to Slave Address 0?
A write to slave address 0 reaches every device on a serial line with no reply - useful, but silent and unverifiable.
Read → GlossaryHow do you budget EtherNet/IP connections?
Count implicit, produced/consumed, listen-only, and messaging connections, use rack-optimized to save count, and leave headroom.
Read → GlossaryBuffered vs Unbuffered Reporting
Choosing a BRCB or URCB by how each handles a client disconnect.
Read → GlossaryHow does CAN baud rate limit cable length?
Arbitration needs a round trip within one bit time, so faster rates force shorter buses; every node must share one rate.
Read → GlossaryHow does CAN bus arbitration work?
Dominant bits override recessive ones so the lowest identifier wins the bus with no collision and the loser retries automatically.
Read → GlossaryWhy does a CAN bus need 120 ohm termination?
Two 120 ohm resistors at the bus ends absorb reflections; a powered-down bus should measure about 60 ohms end to end.
Read → GlossaryWhat is a CAN error frame and bus-off state?
Error counters promote a troubled node from error-active to error-passive to bus-off, isolating a faulty device so the bus survives.
Read → GlossaryWhat is CANopen?
The CiA 301 application layer that turns raw CAN into interoperable devices with an object dictionary, PDOs, SDOs, and network management.
Read → GlossaryWhat is a CANopen COB-ID?
The communication object identifier that packs a function code plus node ID, making a CANopen bus readable straight from the CAN identifiers.
Read → GlossaryWhat is a CANopen object dictionary?
The index and subindex addressed table of a node's parameters, and how the EDS file documents what a gateway can read.
Read → GlossaryWhat is the difference between a CANopen PDO and SDO?
Fast unconfirmed real-time process data objects versus confirmed service data objects for configuration and parameter access.
Read → GlossaryWhat Is the Cause of Transmission (COT) in IEC 60870-5-104?
The COT field that tells the master why an ASDU was sent - spontaneous, cyclic, interrogation, or command.
Read → GlossaryHow do you choose Modbus float word order?
Map ABCD, BADC, CDAB, and DCBA to your driver's byte-swap and word-swap toggles, then confirm against a known value.
Read → GlossaryHow do you choose an RPI for EtherNet/IP I/O?
Match the interval to signal speed and loop need, respect device minimums, and budget total packet load.
Read → GlossaryWhat Is the Difference Between an MQTT Clean Session and a Persistent Session?
Clean vs persistent decides whether the broker keeps a client's subscriptions and queues messages while it is offline.
Read → GlossaryHow do I clear a Modbus illegal data address exception (code 02)?
Reconcile the register map, resolve the 40001 off-by-one, match the function code, and handle span-crossing reads.
Read → GlossaryHow do you commission HART multidrop mode?
Assign unique polling addresses, park each device's loop current, wire the segment in parallel, and poll every address to confirm.
Read → GlossaryConfigure Sparkplug Metric Birth Certificates
Declare every metric with correct name, type, alias, and initial value so later data messages decode reliably.
Read → GlossaryWhat is control in the field with fieldbus?
Running the PID loop inside a Foundation Fieldbus transmitter or positioner instead of the controller.
Read → GlossaryWhat Is a CRC Error in Serial SCADA Communication?
A reply that fails its checksum and is discarded as corrupt - pointing to line noise, not a dead device.
Read → GlossaryData Object and Data Attribute
How IEC 61850 data objects and attributes structure the values inside a logical node.
Read → GlossaryHow do you design a Sparkplug namespace?
Choose group and edge node IDs from stable attributes, keep them unique and character-safe, and plan for fleet growth before you commission.
Read → GlossaryDesign MQTT Topics for an Oilfield Fleet
Lay out a broad-to-specific topic tree so wildcards, access control, and per-site subscriptions scale with the fleet.
Read → GlossaryWhat is a Device-Level Ring (DLR)?
ODVA's EtherNet/IP ring protocol using embedded switches and a beacon-driven supervisor to heal a break in under 3 ms.
Read → GlossaryWhat is DeviceNet?
The CAN-based CIP fieldbus that carries 24V power and data on one cable using MAC IDs and poll/strobe messaging.
Read → GlossaryHow do you diagnose an EtherNet/IP I/O fault?
Read the extended status code first, then work path, RPI and timeout, ownership, and configuration mismatch in order of likelihood.
Read → GlossaryHow do you diagnose PROFINET jitter?
Confirm the fault is timing, separate real-time from background traffic, then check update time and topology in order of likelihood.
Read → GlossaryWhat Is a DNP3 Application Confirmation?
The master acknowledgment that lets an outstation safely clear reported events, and why missing confirms lose or duplicate data.
Read → GlossaryDNP3 Application Layer
Fragments, function codes, object headers, and the IIN status field.
Read → GlossaryDNP3 Broadcast Addressing
Reaching every outstation at once with the reserved broadcast addresses.
Read → GlossaryWhat Is DNP3 Class 0/1/2/3 Data?
DNP3's static Class 0 versus event Class 1/2/3 data model and how class polls differ from the integrity poll.
Read → GlossaryWhat Is a DNP3 Cold Restart?
The full outstation reboot, the Device Restart IIN bit it raises, and how a master re-initializes to avoid stale data.
Read → GlossaryDNP3 Conformance Testing
Verifying a device against the standard, and what it does not prove.
Read → GlossaryWhy do DNP3 control commands fail?
Read the returned status, then work select-operate timing, local mode, object mismatches, and authorization in order.
Read → GlossaryDNP3 Data Set
Bundling mixed point types into one user-defined structure.
Read → GlossaryDNP3 Data-Link Layer
The DNP3 link frame: sync bytes, addresses, and the per-block CRC.
Read → GlossaryDNP3 Device Profile
The standardized document listing exactly what a device supports.
Read → GlossaryWhat do the DNP3 device trouble and local control IIN flags mean?
IIN1.5 local control means a point is in hand mode and rejects remote commands; IIN1.6 device trouble is a device-specific fault.
Read → GlossaryDNP3 Direct Operate vs SBO
One-pass versus two-pass control, and which output uses each.
Read → GlossaryWhat Is a DNP3 Event Buffer?
The fixed queue where a DNP3 outstation stores Class 1/2/3 events, plus overflow, the IIN buffer bit, and RBE.
Read → GlossaryWhat causes the DNP3 event buffer overflow IIN flag?
IIN2.3 means the outstation dropped events because the master polled too slowly, leaving a real historian gap on a healthy link.
Read → GlossaryWhy are DNP3 events not arriving?
Class assignment, deadbands, buffer overflows, missing confirms, and half-enabled unsolicited reporting, in the order to check them.
Read → GlossaryDNP3 File Transfer
Moving configuration, logs, and firmware with the group 70 file object.
Read → GlossaryDNP3 Fragment
The application-layer message unit and why big responses span several.
Read → GlossaryDNP3 Function Code
The read, write, operate, and restart verbs that drive a DNP3 exchange.
Read → GlossaryDNP3 Interoperability Levels
How subset levels 1 to 4 define required objects and functions.
Read → GlossaryWhat does the DNP3 need time IIN flag mean?
IIN1.4 means the outstation clock is untrusted; the master clears it by writing Object 50 so event timestamps stay accurate.
Read → GlossaryWhat Are DNP3 Object Groups and Variations?
How DNP3 organizes data by group and variation, and why the choice controls a pipeline outstation's poll bandwidth.
Read → GlossaryWhat Is a DNP3 Point Index?
The per-object-type address that identifies each binary and analog point in a DNP3 outstation, and how a point map ties it to cloud SCADA tags.
Read → GlossaryDNP3 Qualifier and Range
How an object header names which point indexes a message carries.
Read → GlossaryDNP3 Serial vs TCP
The same frames over RS-485 or an IP socket, and where behavior differs.
Read → GlossaryDNP3 Static Object Variation
Static versus event encodings and how the choice sets byte cost.
Read → GlossaryWhy does DNP3 over TCP keep disconnecting?
Idle firewall and NAT timeouts, half-open sessions after cellular IP changes, and endpoint conflicts, with the fix for each.
Read → GlossaryDNP3 Time Synchronization
How a master sets outstation clocks and why timestamps depend on it.
Read → GlossaryDNP3 Transport Function
How DNP3 segments and reassembles a large fragment across link frames.
Read → GlossaryDNP3 Virtual Terminal
Tunneling a character console through DNP3, and why it needs scrutiny.
Read → GlossaryDNP3 vs IEC 60870-5
Two telecontrol cousins compared and how the choice gets made.
Read → GlossaryDNP3 or Modbus for remote telemetry?
A selection guide comparing event buffering, timestamps, and bandwidth, with a clear rule for when each protocol wins.
Read → GlossaryHow do you capture DNP3 in Wireshark?
Pick a capture point that sees the session, filter with dnp3, and read function codes, confirms, and IIN bits response by response.
Read → GlossaryWhat is DPI-based command filtering for Modbus and DNP3?
Allow Modbus and DNP3 reads while blocking writes mid-stream, so a firewall permits monitoring but stops control.
Read → GlossaryWhat Is EDDL in HART Device Integration?
The declarative language behind DD files that works on any conforming host and outlives the driver-bound alternatives.
Read → GlossaryWhat is an EDS file?
The electronic data sheet describing a device's identity, assemblies, and parameters so a tool can integrate it.
Read → GlossaryWhat are EtherCAT distributed clocks?
How a reference clock, propagation-delay compensation and SYNC signals give sub-microsecond sync across slaves.
Read → GlossaryWhat is EtherCAT Hot Connect?
How defined slave groups can be connected or removed during operation without faulting the segment, for modular machines.
Read → GlossaryEtherNet/IP
The CIP-based industrial Ethernet behind Allen-Bradley controllers - messaging types and reading tags into cloud SCADA.
Read → GlossaryWhat ports does EtherNet/IP use?
TCP 44818 for explicit messaging and UDP 2222 for cyclic I/O - the split that shapes firewalls and diagnostics.
Read → GlossaryWhat Does Modbus Function Code 43 (Read Device Identification) Do?
The MEI type 14 read that returns vendor name, product code, and firmware revision so tools can auto-detect a device.
Read → GlossaryWhat Is a Fieldbus Device Coupler?
The junction block connecting spurs to the trunk with per-spur fault protection, so one bad device cannot kill the segment.
Read → GlossaryWhat Is a Fieldbus Power Conditioner?
The device that feeds DC to an H1 segment without shorting out the digital signal on the same pair.
Read → GlossaryWhat Is a Fieldbus Segment?
The H1 trunk-and-spur cable that powers and talks to many field devices on one shared bus.
Read → GlossaryWhat Is a Fieldbus Terminator?
The RC network at each end of an H1 segment that absorbs the signal so it does not reflect and distort.
Read → GlossaryHow to Find a HART Device at an Unknown Address
Poll address 0 first, then scan the whole polling-address range, read command 0 on any hit, and rule out wiring.
Read → GlossaryWhat is FISCO in fieldbus wiring?
The Fieldbus Intrinsically Safe Concept: a simplified way to run a safe fieldbus segment with more devices.
Read → GlossaryHow do I fix a Modbus timeout or slave-not-responding error?
Diagnose in order: wrong unit ID, offline device, blocked port 502, poll-timing tuning, and gateway remaps.
Read → GlossaryWhy is my Modbus register showing a wrong or garbled value?
Diagnose byte and word order, floats split across two registers, signed vs unsigned, and scaling factor errors.
Read → GlossaryFix a Sparkplug Sequence Number Mismatch
Read the gap as a symptom of message loss, resynchronize with a rebirth, and fix the QoS or path underneath.
Read → GlossaryFix a Sparkplug Stale Metric After Reconnect
Trace a frozen metric to a missed birth or rebirth and get the consumer's model back in sync with the node.
Read → GlossaryFix an MQTT Broker Dropping Messages Under Load
Order the load causes - slow consumer, queue limit, host resources - and verify the fix under a reproduced peak.
Read → GlossaryFix an MQTT Client Connecting Then Disconnecting
Order the causes of an immediate drop - duplicate client ID, keepalive, authorization - and test each.
Read → GlossaryHow do you fix an MQTT reconnect loop?
Duplicate client IDs, keep-alive versus the real network, and auth rejections - read the broker log and the loop's rhythm first.
Read → GlossaryFix an OPC UA Subscription Not Delivering Changes
Order the causes of a silent subscription - monitoring mode, publishing flag, deadband, revised interval.
Read → GlossaryHow do you fix EtherNet/IP timeouts?
Split never-connects from connects-then-dies: sizes and ownership for the first, RPI, congestion, and multicast IGMP for the second.
Read → GlossaryHow do you fix a multicast storm?
Confirm flooding from port stats, enable IGMP snooping with a querier, and segregate I/O traffic onto its own VLAN.
Read → GlossaryWhy is a HART multidrop device not responding?
Poll it in isolation to split device from loop, then work duplicate address, power budget, and physical-layer noise in order.
Read → GlossaryHow do you fix Modbus float byte and word order?
Compare to a known value, then try word swap, byte swap, and both in order until the float reads right; set it per device.
Read → GlossaryHow do you fix Modbus RTU CRC errors?
Trace corrupted frames to port mismatches, termination and biasing faults, grounding trouble, or bad cable, in likelihood order.
Read → GlossaryWhy is my Modbus gateway returning stale values?
Confirm the freeze against the device display, localize it to the gateway, disable or shorten its cache, and verify live reads.
Read → GlossaryWhy is Modbus TCP reading the wrong device?
Confirm the crossover with a device-unique read, then fix a shared unit ID, colliding serial address, duplicate IP, or connection reuse.
Read → GlossaryWhy does Modbus TCP read all zeros?
The connection is fine - the addressing is not. Wrong register area, off-by-one offsets, unit ID routing, and wrong-target traps.
Read → GlossaryHow do you fix Modbus TCP unit-ID confusion?
Decide gateway vs native, set the unit ID to the target serial address, resolve address collisions, and verify each device answers as itself.
Read → GlossaryWhy is a Modbus value off by a factor of ten?
A missing implied decimal; recover the divisor from the map or empirically, apply it once, and verify at two points.
Read → GlossaryFix MQTT Messages Out of Order or Dropped
Separate reordering from loss, then check QoS, session persistence, concurrency, and inflight limits by likelihood.
Read → GlossaryFix MQTT Retained Message Problems
Diagnose stale values, ghost readings, and retained messages that will not clear, each with its test and fix.
Read → GlossaryFix OPC UA BadTooManyMonitoredItems
Find which capacity ceiling you hit and spread items across subscriptions or sessions to clear the rejection.
Read → GlossaryHow do you fix OPC UA certificate errors?
Find which side rejected, approve from the rejected store, then rule out expiry, regeneration, chains, clocks, and URI mismatches.
Read → GlossaryFix OPC UA Reads Failing After Browse
Browse works but reads return access-denied - check identity, role, and node access attributes in order.
Read → GlossaryHow do you fix OPC UA session timeouts?
Identify which layer expires - session, secure channel, or idle TCP - then align keep-alive traffic and timeouts to stop the loop.
Read → GlossaryFoundation Fieldbus
The all-digital process bus for refineries and gas plants - H1, HSE, control-in-the-field, and its path to SCADA.
Read → GlossaryWhat Is the Difference Between Modbus Function Code 16 and Function Code 6?
FC06 writes one holding register, FC16 writes a block atomically - why 32-bit values need FC16 and how to choose.
Read → GlossaryFunctional Constraint
The two-letter FC tags that group IEC 61850 attributes by role, such as ST, MX and CF.
Read → GlossaryHow Does a Modbus Gateway Remap Unit IDs Between Serial and TCP?
How a serial-to-TCP gateway maps RS-485 slave addresses behind one IP and routes a poll to the right RTU.
Read → GlossaryWhat Is an IEC 61850 GOOSE Message?
The fast layer-2 multicast that carries substation protection trips and interlocks between IEDs.
Read → GlossaryHow Does GOOSE Retransmission and Heartbeat Timing Work?
The slow heartbeat, the post-event burst, and the counters and time-to-live that make GOOSE reliable.
Read → GlossaryGOOSE vs MMS vs SV Roles
Side-by-side of the three IEC 61850 services and which traffic each one carries.
Read → GlossaryHow do you ground and shield a fieldbus segment?
Keep the shield continuous end to end, ground it at one point, float the field ends, and verify no second ground forms a loop.
Read → GlossaryWhat Changed in HART 7?
The revision that added WirelessHART, richer diagnostics, event notification, and longer tags, and why revision affects compatibility.
Read → GlossaryWhat is HART burst mode?
Publish mode where a HART device continuously broadcasts its variables without being polled, updating faster.
Read → GlossaryWhat Does HART Command 3 Do?
The universal read that returns loop current and all four dynamic variables in one exchange - the workhorse polling command.
Read → GlossaryHART Universal vs Device-Specific Commands
The three command tiers that decide what a generic host can read and where a device description file becomes mandatory.
Read → GlossaryWhy can't my HART communicator find the device?
Loop resistance, clip points, hidden polling addresses, and marginal loop power - the field check sequence in likelihood order.
Read → GlossaryWhat Is a HART Device Description (DD) File?
The EDDL file that teaches a generic host a device's variables, commands, and menus so it can be configured without vendor software.
Read → GlossaryHART Device Variables vs Dynamic Variables
How raw device measurements map into the four PV, SV, TV, QV slots, and why the analog current only ever tracks the PV.
Read → GlossaryWhat Is a HART DTM and FDT Frame?
How a vendor's device type manager plugs into an FDT frame, and how a DTM differs from a portable DD file.
Read → GlossaryHow the HART FSK Physical Layer Works
Bell 202 tones at 1200 and 2200 Hz ride on the 4-20 mA current and average to zero, so digital data never moves the analog value.
Read → GlossaryWhat Is a HART Long-Frame Device Address?
The globally unique identifier built from manufacturer, type, and serial that lets a host reach one exact instrument.
Read → GlossaryWhat Is a HART Loop?
How a digital signal rides on the same 4-20 mA wires as the analog reading, plus point-to-point vs multidrop.
Read → GlossaryHART Primary and Secondary Master Roles
How two masters share one loop through token-passing arbitration, and why a role conflict stops a handheld from reaching a device.
Read → GlossaryWhat Is HART Multidrop?
The mode that puts many transmitters on one pair by fixing their current and going digital-only.
Read → GlossaryWhat Is the HART Preamble and Message Timing?
Why each frame starts with sync bytes, how required preamble length varies by device, and how timing rules avoid collisions.
Read → GlossaryHART Protocol
How smart digital signals ride on 4-20 mA loops, WirelessHART, and getting stranded instrument diagnostics into SCADA.
Read → GlossaryWhat Are HART Response Codes?
How a device signals success, a communication error, or a command-specific rejection like out-of-range or write-protected.
Read → GlossaryWhat Is the HART Device Status Byte?
The two status bytes in every response whose flags tell a host whether a reading is trustworthy or from a faulted device.
Read → GlossaryWhat is a HART Tri-Loop?
A converter that splits a multivariable transmitter's extra HART variables into separate 4-20 mA outputs.
Read → GlossaryWhat is HART-IP?
HART commands and multivariable digital data carried over Ethernet, the uplink from WirelessHART gateways and multiplexers.
Read → GlossaryWhat Is Hazardous Area I/O and How Is It Made Safe?
IS barriers and isolators for Zone 0/1 devices versus non-incendive Division 2 modules mounted in the field.
Read → GlossaryHow do I map a Modbus device in SCADA?
Set the connection and unit ID, map coils and registers with the right function code, then fix word order and scaling.
Read → GlossaryWhat is the difference between HSR and PRP network redundancy?
Both are IEC 62439-3 zero-loss schemes: PRP duplicates over two parallel LANs, HSR around one ring.
Read → GlossaryHow do you plan IEC 104 addressing?
Registry-managed common addresses, IOA ranges by signal kind with growth gaps, and one controlled table every hop implements.
Read → GlossaryHow does IEC 104 general interrogation work?
Command, confirmation, interrogated data, termination - triggered at session start, after outages, and on a modest backstop schedule.
Read → GlossaryHow do you tune IEC 104 protocol parameters?
k and w set the in-flight window, t1 and t2 the acknowledgment patience, t3 the idle heartbeat - measured against the real link.
Read → GlossaryWhy are IEC 104 timestamps wrong?
Timezone-sized offsets mean convention mismatch, drift means no sync, epoch means unset clock, impossible order means mixed sources.
Read → GlossaryIEC 60870-5 ASDU Types
How type identifiers sort telecontrol data into status, measured, command and system kinds.
Read → GlossaryIEC 60870-5 Cause of Transmission Table
The reasons an ASDU is sent - spontaneous, interrogation, activation - and how each is read.
Read → GlossaryIEC 60870-5-101 vs 104
Serial versus TCP/IP telecontrol, and the application layer the two companion standards share.
Read → GlossaryIEC 60870-5-104
The TCP/IP telecontrol protocol behind utility SCADA - ASDUs, cause of transmission, and how -104 data integrates.
Read → GlossaryIEC 60870-5-104 APDU, APCI, ASDU
How a 104 frame nests, and how the I, S and U formats drive its flow control.
Read → GlossaryIEC 61850
The digital-substation standard - logical nodes, MMS, GOOSE, and Sampled Values, and how its data reaches SCADA.
Read → GlossaryIEC 61850 Conformance Testing
What conformance testing proves, the PICS/PIXIT/MICS documents, and its interoperability limit.
Read → GlossaryIEC 61850 Dataset
The ordered collection of data references that a report or GOOSE control block publishes.
Read → GlossaryIEC 61850 Edition 1 vs Edition 2
What Edition 2 changed and why mixed-edition substations need verification.
Read → GlossaryIEC 61850 Logical Node Naming
How LN names are built from prefix, class, instance and suffix, plus LLN0 and LPHD.
Read → GlossaryWhat are IEC 61850 Sampled Values (SV)?
How digitized CT and VT streams replace copper wiring on the substation process bus.
Read → GlossaryIEC 61850 series structure, explained by part
How the series separates the abstract data model and SCL configuration from the MMS, GOOSE, and Sampled Values mappings, part by part.
Read → GlossaryIEC 61850 vs IEC 60870-5
Substation automation versus telecontrol, and how the two IEC standards coexist.
Read → GlossaryIEC 61850-90-5 (R-GOOSE, R-SV)
Routable GOOSE and SV over IP for wide-area and synchrophasor applications.
Read → GlossaryInformation Object Address (IOA)
How the IOA and common address uniquely identify a point, and how to plan the address space.
Read → GlossaryHow do you fix intermittent I/O faults from EMI?
Correlate drops with machine events, read error counters, then fix with routing, shielding, and grounding and confirm on the counters.
Read → GlossaryWhat Is the DNP3 Internal Indication (IIN) Field?
Two status bytes in every DNP3 response - restart, need-time, events available, buffer overflow - that a master acts on.
Read → GlossaryWhat is IO-Link?
A point-to-point serial link that adds digital data, parameters and diagnostics to smart sensors over three-wire cable.
Read → GlossaryLay Out a Sparkplug Group and Node ID Scheme
Map Group, Node, and Device IDs to real dimensions with stable, unique values so the fleet namespace scales.
Read → GlossaryLLDP and PROFINET topology
Port-by-port neighbor detection that drives topology display, fault location, and device replacement.
Read → GlossaryLogical Device
The grouping of logical nodes inside an IED, and why LLN0 and LPHD are always present.
Read → GlossaryLogical Node
The smallest IEC 61850 function block and how its four-letter class names work.
Read → GlossaryMap OPC UA Nodes to Sparkplug Metrics
Reconcile the two type and quality systems and declare the full metric set at birth so the consumer decodes clean.
Read → GlossaryWhat is the Media Redundancy Protocol (MRP)?
The IEC 62439-2 ring standard common in Profinet, where a manager heals a single break in about 200 ms.
Read → GlossaryWhat is a merging unit in a digital substation?
The device that samples CT/VT signals, timestamps them via PTP, and publishes Sampled Values.
Read → GlossaryWhat Are Sparkplug Metric Aliases and Sequence Numbers For?
Aliases shrink NDATA payloads for cellular links; the rolling seq number detects missed messages and triggers a rebirth.
Read → GlossaryMMS (61850)
The client-server protocol carrying routine IEC 61850 traffic over TCP/IP.
Read → GlossaryModbus ADU vs PDU
The transport-independent PDU and the transport-specific ADU that wraps it.
Read → GlossaryModbus CRC-16 Checksum
The two-byte RTU frame check: what it covers, how it fails silently, and why TCP omits it.
Read → GlossaryWhat Is a Modbus Exception Code?
Decode responses 01, 02, 03, 04 to tell whether the map is wrong, the register is missing, or the device has faulted.
Read → GlossaryModbus Exception Code 04 (Slave Device Failure)
The device-side error: what triggers exception 04 and why it differs from 01 to 03.
Read → GlossaryModbus Exception Code 06 (Server Device Busy)
The transient busy signal: when a device raises code 06 and why you retry, not refix.
Read → GlossaryModbus Exception Codes Reference Table
Every standard exception code in one table, grouped by request, device, or gateway.
Read → GlossaryWhy does a Modbus tag read fine on FC3 but throw an exception on FC4?
How input registers differ from holding registers in a vendor map, and setting the correct read function per tag.
Read → GlossaryWhat Is a Modbus Function Code?
The verb in every Modbus request - codes 01 to 16 - which reads a sensor, which writes a command, and why a wrong code fails.
Read → GlossaryModbus Function Code 01 (Read Coils)
How FC01 reads the coil table, packs its reply, and why it is not a register read.
Read → GlossaryModbus Function Code 02 (Read Discrete Inputs)
How FC02 reads the read-only discrete-input table and why it has no write code.
Read → GlossaryModbus Function Code 03 (Read Holding Registers)
The workhorse read: FC03 targets, its 125-register limit, and FC03 versus FC04.
Read → GlossaryModbus Function Code 04 (Read Input Registers)
How FC04 reads the read-only input-register table and how it differs from FC03.
Read → GlossaryModbus Function Code 05 (Write Single Coil)
The single-coil write, its 0xFF00 and 0x0000 encoding, and FC05 versus FC15.
Read → GlossaryModbus Function Code 06 (Write Single Register)
The single-register write, its echo confirmation, and FC06 versus FC16.
Read → GlossaryModbus Function Code 07 (Read Exception Status)
The short serial status-byte read, and why it is not a Modbus exception code.
Read → GlossaryModbus Function Code 08 (Diagnostics)
The serial diagnostics verb: loopback link tests and the device's own error counters.
Read → GlossaryModbus Function Code 15 (Write Multiple Coils)
The multi-coil write, its packed-bit format, and why it beats repeated FC05 writes.
Read → GlossaryModbus Function Code 16 (Write Multiple Registers)
The multi-register write, its 123-register limit, and why it safely sets 32-bit values.
Read → GlossaryModbus Function Code 17 (Report Server ID)
The device-identification and run-status command, and how it compares with FC43.
Read → GlossaryWhat do Modbus exceptions 0A and 0B mean?
Gateway-generated codes that split the fault: 0A is a routing or mapping problem, 0B is silence from the serial device downstream.
Read → GlossaryHow do you fix a Modbus exception code 03 (illegal data value)?
Exception 03 means your value is out of range, not a bad address. Causes, how to isolate it, and how it differs from 02.
Read → GlossaryWhat causes a Modbus exception code 01 (illegal function)?
Exception 01 means the slave does not support the function code you sent. Common triggers and a decision path to fix it.
Read → GlossaryWhat Is a Modbus Illegal Data Address Exception (Code 02)?
Exception 02 means the polled register does not exist - a pinpoint addressing bug, not a dead link.
Read → GlossaryModbus LRC Checksum
The single-byte ASCII-mode checksum, how it is formed, and why it is weaker than a CRC.
Read → GlossaryModbus MBAP Header
The four TCP header fields explained: transaction ID, protocol ID, length, and unit ID.
Read → GlossaryModbus over TLS
Encryption and mutual authentication wrapped around unchanged Modbus TCP messages.
Read → GlossaryWhat is Modbus Plus?
Modicon's legacy 1 Mbit/s token-passing peer-to-peer network, distinct from Modbus RTU and TCP, that needs a gateway.
Read → GlossaryWhat Is Modbus 40001 vs 0-Based Addressing?
Why 40001 is really offset 0 with function code 03, where the off-by-one comes from, and how to align a vendor map.
Read → GlossaryModbus Register Data Types and Packing
How int32, float, and string values pack across raw 16-bit registers by convention.
Read → GlossaryModbus RTU vs ASCII Transmission Mode
The two serial modes compared: binary CRC framing versus colon-delimited ASCII with an LRC.
Read → GlossaryWhat is Modbus serial response delay and turnaround time?
The 3.5-character silent interval and transmit turnaround, and how to tune the wait on slow radios and RS-485 links.
Read → GlossaryWhat is a Modbus swapped 32-bit integer word order?
How signed and unsigned counters span two registers, the four decode permutations, and picking the right one.
Read → GlossaryModbus TCP Port 502
The registered Modbus port, its role in firewalls, and why an open 502 is a risk.
Read → GlossaryModbus TCP or EtherNet/IP for a skid?
A selection guide: match the skid interface to whatever reads it, with a data-model table and the integration traps for each.
Read → GlossaryWhat Is Modbus TCP vs RTU?
Binary RTU over RS-485 with a CRC vs Modbus TCP over Ethernet with an MBAP header, and how a gateway bridges them.
Read → GlossaryWhat Is a Modbus Timeout and Why Does a Slave Stop Responding?
The no-reply fault on a Modbus link, its usual causes, and how retries turn it into a comms-fail alarm.
Read → GlossaryModbus Transaction Identifier
The MBAP field that pairs each TCP reply with its request and enables pipelining.
Read → GlossaryWhat Is a Modbus Unit ID?
The RS-485 slave address vs the Modbus TCP Unit ID, and how a gateway routes one IP to many chained field devices.
Read → GlossaryWhat is Modbus zero-based vs one-based addressing?
The gap between the zero-based wire address and one-based documentation numbering, and the per-device base fix.
Read → GlossaryWhat is an MQTT bridge?
A broker-to-broker link that forwards selected topics from a site broker up to a cloud broker.
Read → GlossaryWhat is MQTT receive maximum and flow control?
The MQTT 5 cap on unacknowledged in-flight messages that provides backpressure so a slow gateway is not flooded.
Read → GlossaryWhat is MQTT keepalive?
The idle interval before a client must PINGREQ, how the broker uses 1.5x to detect a dead node, and how to size it for cellular.
Read → GlossaryWhat Is an MQTT Last Will (LWT)?
How a client registers a will the broker publishes on an ungraceful disconnect, giving fast dead-node detection and underpinning Sparkplug birth and death certificates.
Read → GlossaryWhat is the MQTT message expiry interval?
The MQTT 5 property that discards queued telemetry after a set time so a reconnecting client is not flooded with stale readings.
Read → GlossaryWhat are MQTT no local and retain as published?
The MQTT 5 subscription options that stop a client hearing its own echo and preserve the retain flag across a bridge, preventing loops and lost state.
Read → GlossaryWhat Are MQTT QoS Levels (0, 1, 2)?
QoS 0 fire and forget, QoS 1 at least once, and QoS 2 exactly once - their overhead, loss risk, and how to pick a level for a flaky cellular link.
Read → GlossaryWhat is an MQTT reason code?
The MQTT 5 byte that states why a connect, publish, subscribe, or disconnect succeeded or failed, plus the optional human-readable reason string.
Read → GlossaryWhat is MQTT request/response?
The MQTT 5 response topic and correlation data properties that let a client send a command and reliably match the reply over one-way pub/sub.
Read → GlossaryWhat is the MQTT retain handling option?
The MQTT 5 subscription option that controls whether subscribing delivers the existing retained message, key to avoiding a flood on reconnect.
Read → GlossaryWhat Is an MQTT Retained Message?
How the retain flag makes the broker hold a topic's last value so a new or reconnecting client gets the current value instantly, and how it differs from a last will.
Read → GlossaryWhat is MQTT session expiry and clean start?
The MQTT 5 timer and flag governing how long the broker holds queued messages for a flapping gateway.
Read → GlossaryWhat is an MQTT shared subscription?
A $share group that load-balances one topic stream across several consumers, one message each.
Read → GlossaryWhat is an MQTT subscription identifier?
The MQTT 5 integer the broker echoes on matching messages so a client can dispatch a publish to the right handler without re-matching topics.
Read → GlossaryWhat is an MQTT topic alias?
An MQTT 5.0 shorthand that replaces a long topic with a small integer to cut per-message bytes.
Read → GlossaryWhat Is an MQTT Topic Hierarchy?
How slash-delimited topics form a namespace and how the plus and hash wildcards let a subscriber grab a whole area of a field at once.
Read → GlossaryWhat is an MQTT user property?
The MQTT 5 custom key-value header pair for attaching units, source, or version metadata to a message without touching the payload.
Read → GlossaryWhat is the MQTT will delay interval?
An MQTT 5.0 grace period that holds the Last Will so a quick reconnect avoids a false offline event.
Read → GlossaryHART Multidrop vs WirelessHART: Which to Use
Wiring, power, update rate, and scalability compared, with clear guidance on when reusing wire or going wireless wins.
Read → GlossaryWhat Are Sparkplug NBIRTH and NDEATH Messages?
NBIRTH publishes an edge node's full metric set on connect; NDEATH, set as the MQTT last will, signals it has died.
Read → GlossaryWhat is the difference between CANopen node guarding and heartbeat?
Master-polled guarding with a toggle bit versus node-produced heartbeat messages, and why heartbeat is preferred for alarms.
Read → GlossaryWhat is OCPP (Open Charge Point Protocol)?
The open standard linking EV chargers to a central management system, carrying status, meter values, and remote control.
Read → GlossaryOPC Classic vs OPC UA
The interoperability standard of automation - why DCOM held OPC Classic back and how OPC UA's model changed integration.
Read → GlossaryWhat Is an OPC Quality Code and Its Substatus?
Decoding good, uncertain, and bad plus substatus like last usable value, sensor failure, and comm failure.
Read → GlossaryOPC Tunnel
Tunneling software that carries OPC data across networks and firewalls over a single TCP connection, replacing fragile DCOM.
Read → GlossaryWhat Is the OPC UA Address Space?
How OPC UA data forms a browsable graph of nodes and references, and why a self-describing model lets cloud SCADA discover a facility's assets.
Read → GlossaryWhat Is an OPC UA Endpoint URL?
The opc.tcp address on port 4840 plus its security policy and message mode, how discovery lists endpoints, and why the wrong security blocks a connection.
Read → GlossaryWhat Is an OPC UA Node ID?
The unique address of a node built from a namespace index and identifier, how it differs from a Modbus register, and how a client reads a value with it.
Read → GlossaryWhat is OPC UA PubSub vs client-server?
Client-server sessions and monitored items versus PubSub publishing UADP or JSON over UDP or MQTT for one-to-many telemetry.
Read → GlossaryWhat Is an OPC UA Subscription?
How push-style delivery uses sampling interval, publishing interval, and deadband to send only changed values, saving bandwidth versus constant polling.
Read → GlossaryWhat is an OPC UA to MQTT bridge?
Converting request/response OPC UA into publish/subscribe MQTT at the edge, mapping node IDs to topics and Sparkplug metrics.
Read → GlossaryOPC UA or Modbus for a new integration?
A selection guide comparing self-describing security against simple universal registers, with a rule for greenfield links.
Read → GlossaryOPC UA or MQTT for enterprise integration?
A selection guide comparing rich information models against lightweight push, with the edge-collect, cloud-transport pattern.
Read → GlossaryPlain MQTT or Sparkplug for SCADA?
A side-by-side on freedom versus convention: what Sparkplug's state model and self-describing payload add, and when plain MQTT still fits.
Read → GlossaryWhat is a produced/consumed tag?
The cyclic controller-to-controller connection that shares live data peer-to-peer without a scanner.
Read → GlossaryPROFIBUS
The classic industrial fieldbus - DP for discrete control, PA for process instruments - and how its field data reaches modern SCADA.
Read → GlossaryPROFIBUS address and HSA
Unique node numbers 0 to 126 and the HSA that bounds the token's search for masters.
Read → GlossaryPROFIBUS DP bus cycle
Token passing between masters plus polled request-response to each slave.
Read → GlossaryPROFIBUS DP diagnostics
A slave flags a fault in its cyclic reply; the master reads standard plus extended diagnosis.
Read → GlossaryPROFIBUS DP master class
DPM1 runs the cyclic control; DPM2 is the engineering and diagnostic station.
Read → GlossaryPROFIBUS DP termination
Active termination that also biases the bus - why it lives at segment ends and must stay powered.
Read → GlossaryWhat is the difference between Profibus DP and Profibus PA?
Fast RS-485 DP for discrete I/O versus slow two-wire bus-powered PA for process instruments, bridged by a coupler.
Read → GlossaryPROFIBUS DP-V0/V1/V2
Cyclic I/O, then acyclic parameter access, then isochronous and clock features.
Read → GlossaryDP/PA coupler vs link
Transparent converter versus a gateway that represents the PA segment as one slave.
Read → GlossaryPROFIBUS PA MBP signaling
Manchester Bus Powered - data and power on one pair, suited to intrinsically safe segments.
Read → GlossaryPROFINET
Real-time industrial Ethernet from PI - RT and IRT explained, and how PROFINET plants connect to SCADA and the cloud.
Read → GlossaryPROFINET alarm frame
The acyclic, acknowledged message that reports diagnosis, pull/plug, and return-of-submodule events.
Read → GlossaryPROFINET AR and CR
The application relation is the connection; the communication relations are the IO, alarm, and record pipes inside it.
Read → GlossaryWhat is a Profinet conformance class (CC-A, CC-B, CC-C)?
Certified capability tiers that define whether a Profinet device offers topology discovery, diagnostics or full IRT.
Read → GlossaryPROFINET DCP
The layer-2 protocol that discovers devices and assigns station names and IP before any IO connection.
Read → GlossaryHow do you fix a PROFINET name mismatch?
The station name lives in the device: assign it via DCP after a swap, or configure topology so replacement is automatic.
Read → GlossaryPROFINET diagnostics model
Channel, module, and device diagnosis nested so a fault names the exact failing terminal.
Read → GlossaryPROFINET Fast Startup
Fixed port settings and streamlined init to rejoin the network fast - built for tool changers.
Read → GlossaryWhat is the difference between Profinet RT and IRT?
Prioritised Real-Time Ethernet frames versus hardware-scheduled Isochronous Real-Time with sub-microsecond jitter for motion.
Read → GlossaryPROFINET isochronous mode
Ti and To offsets lock every axis to sample and actuate at the same instant for motion.
Read → GlossaryHow do you diagnose PROFINET with LLDP?
Read each port's reported neighbor, compare the live neighborhood to the planned topology, and fix the cable or the plan at the mismatch.
Read → GlossaryPROFINET security classes
Classes 1, 2, and 3 layer hardening, then authentication, then encryption.
Read → GlossaryPROFINET shared device
One physical device whose submodules are split between two or more controllers.
Read → GlossaryPROFINET system redundancy
S2 and R1 keep IO running through a controller failover by holding standby relations.
Read → GlossaryPROFINET update time
Send clock times reduction ratio - how each device gets its own cyclic rate on one network.
Read → GlossaryPROFINET or EtherNet/IP for a machine?
A selection guide comparing ecosystem fit, device availability, and integration effort, with a rule that follows the controller.
Read → GlossaryProtocol Converter
The device that translates one industrial protocol or signal into another so mismatched field equipment and SCADA can exchange data.
Read → GlossaryProtocol Gateway
The translators that bridge Modbus, PROFIBUS, HART, and OPC UA so mixed-vintage devices reach modern cloud SCADA.
Read → GlossaryWhy Does MQTT QoS 1 Deliver Duplicate Messages?
A lost PUBACK makes the publisher resend with the DUP flag - at-least-once delivery means consumers must be idempotent.
Read → GlossaryHow do you read Modbus 30001 vs 40001?
Read the leading digit to pick FC04 or FC03, then strip the prefix and subtract one for the wire offset.
Read → GlossaryWhat Is Register Byte Order (Endianness) in Modbus?
Why a 32-bit Modbus float reads as garbage until word and byte order are set to match the device.
Read → GlossaryWhat Is a Modbus Register Map and How Do You Read One?
How to read the vendor address table - address, type, data type, scaling, access - and build a working poll from it.
Read → GlossaryReport Control Block
How IEC 61850 RCBs push MMS reports, with trigger options and buffered vs unbuffered behavior.
Read → GlossaryWhat Is RS-232 Serial Communication?
The single-ended point-to-point serial standard wired between RTUs, radios, and flow computers.
Read → GlossaryRS-485 / Serial
The differential serial standard behind Modbus RTU and PROFIBUS - multidrop wiring, RS-232 vs RS-485, and serial in SCADA.
Read → GlossaryHow do you fix RS-485 turnaround problems?
Clipped replies through converters come from direction-control timing: automatic control, baud config, biasing, and response delays.
Read → GlossarySCL Files
ICD, CID, SCD, SSD and IID: what each SCL file type describes and how they hand off.
Read → GlossaryWhat is secure protocol tunneling for legacy SCADA?
Wrapping cleartext Modbus or DNP3 in an encrypted tunnel for confidentiality and integrity, without touching the endpoints.
Read → GlossaryWhat Is Select-Before-Operate (SBO)?
DNP3's two-step arm-then-fire control handshake, its select timeout window, and how it differs from direct-operate.
Read → GlossaryWhat Is a Serial Device Server?
The multiport appliance that puts legacy serial RTUs and meters on an IP network via virtual COM ports or raw TCP.
Read → GlossaryWhat Is Serial Flow Control?
Hardware RTS/CTS vs software XON/XOFF handshaking, and RTS keying of a serial radio transmitter.
Read → GlossaryWhat Is Serial Parity and Framing?
The 8N1 and 8E1 shorthand for data bits, parity, and stop bits, and how they catch line errors.
Read → GlossaryHow do you set DNP3 analog deadbands?
Measure the noise band, set the deadband just above it in the right units, and verify the event rate and buffer behavior after.
Read → GlossaryHow do you set electronic keying?
Choose the level for the situation, match the expected revision, apply it, and verify the connection opens.
Read → GlossarySet OPC UA Monitored Item Queue Size
Size the per-item queue to your sample-per-publish ratio so fast changes are not silently dropped.
Read → GlossarySet OPC UA Sampling and Publishing Intervals
Order the two interval settings correctly so an OPC UA subscription carries every real change and no empty traffic.
Read → GlossarySet Up MQTT Last Will for Offline Detection
Pair a retained will with a birth message and a will delay so fleet availability is accurate and does not flicker.
Read → GlossaryHow do you size an EtherNet/IP RPI?
Work the 2N/RPI packets-per-second math, then check it against the connection, CPS, and adapter-minimum ceilings.
Read → GlossarySparkplug B
The MQTT specification that makes IIoT data SCADA-ready - birth/death certificates, report-by-exception, and unified namespace.
Read → GlossaryWhat is Sparkplug bdSeq and seq numbering?
The two Sparkplug counters: seq orders messages to catch gaps, and bdSeq pairs a birth with its death so a stale will is ignored.
Read → GlossaryWhat is a Sparkplug dataset metric?
A metric datatype that carries tabular rows and typed columns in one payload, for recipes, lookup curves, or multi-row status.
Read → GlossaryWhat is a Sparkplug DCMD and NCMD command?
The command messages that push setpoints and control writes down to an edge node or a device behind it.
Read → GlossaryWhat are Sparkplug DDATA and NDATA messages?
The Sparkplug data messages that carry ongoing metric changes for a device and edge node, sent on change and identified by alias after birth.
Read → GlossaryWhat is a Sparkplug DDEATH message?
The Sparkplug device death message that marks one device offline while its edge node stays alive, so only that device's data is flagged stale.
Read → GlossaryWhat is the difference between a Sparkplug edge node and a device?
How one gateway (the edge node) fans out to many devices via the group/node/device topic hierarchy.
Read → GlossaryWhat are Sparkplug metric datatype and metadata?
How each metric declares its type and can carry descriptive metadata, making the payload self-describing so no external tag dictionary is needed.
Read → GlossaryWhat is a Sparkplug primary host application?
The consuming host edge nodes watch via STATE - losing it, not the broker, triggers store-and-forward.
Read → GlossaryWhat is a Sparkplug property set?
The named, typed descriptors attached to a metric that carry units, ranges, or quality alongside the value so context travels with the data.
Read → GlossaryWhat is a Sparkplug rebirth request?
A host writing Node Control/Rebirth to make a stalled edge node re-emit its full birth certificate.
Read → GlossaryWhat is a Sparkplug template?
A reusable metric structure defined once and instanced many times to model repeated assets like pumps or wells as typed objects.
Read → GlossarySparkplug or plain MQTT for SCADA?
A selection guide comparing state awareness and typed payloads against raw flexibility, with a rule for adoption.
Read → GlossaryWhat is the difference between a fieldbus spur and trunk?
The trunk is the shared home-run backbone; spurs are the short drops to devices, each with its own rules.
Read → GlossaryWhat Do STARTDT and STOPDT Do in IEC 60870-5-104?
The control frames that start and stop 104 data flow on an open TCP connection, plus TESTFR keepalives.
Read → GlossaryStation Bus vs Process Bus
The two IEC 61850 networks, the traffic each carries, and why they stay separate.
Read → GlossaryWhat Is Tag Browsing in OPC?
Navigating an OPC server's address space to discover available nodes before subscribing, and how tools use it to map tags.
Read → GlossaryHow do I test an RS-485 serial SCADA link?
Multimeter and scope procedure: verify A/B polarity, idle bias, 120-ohm termination, daisy chain, and node faults.
Read → GlossaryHow do you troubleshoot a CAN bus?
Cheapest first: confirm 60 ohm termination, verify baud rate, inspect wiring and grounds, then read error counters to localize the node.
Read → GlossaryHow do you troubleshoot a DLR ring fault?
Read the ring supervisor, localize the break between two nodes, fix it, and confirm the ring closes again.
Read → GlossaryWhy does my MQTT Sparkplug edge node keep going offline?
Find the real trigger: keep-alive firing NDEATH, sequence gaps, duplicate client IDs, or QoS and session settings.
Read → GlossaryHow do you find one bad node on RS-485?
Rule out a bus-level fault, then isolate nodes by halves until removing one device brings the whole bus back.
Read → GlossaryTune MQTT Inflight and Queue Limits
Size the inflight window and send queue to a slow link's latency so publishes neither stall nor drop.
Read → GlossaryWhat Is the Difference Between a DNP3 Update Key and Session Key?
A long-lived pre-shared update key protects short-lived session keys that rotate often to shrink the blast radius.
Read → GlossaryHow do you verify a Sparkplug birth certificate?
Capture the NBIRTH raw, confirm the topic, check every metric's name, datatype, and alias, and prove the birth precedes any data.
Read → GlossaryVerify an OPC UA Server Endpoint
Prove reachability, security policy, and identity with a test client before wiring the server into production.
Read → GlossaryHow do you verify DNP3 time sync?
Watch Need Time servicing, check the master's clock source, then force a test event and compare its timestamp to a reference.
Read → GlossaryHow do you verify an EDS or GSD file version?
Read the field device's real revision, read the file's declared revision, and confirm the project's catalog entry matches both.
Read → GlossaryVerify Sparkplug Data Reaches a Historian
Check birth consumption, end-to-end values, source timestamps, and quality so the stored history is faithful.
Read → GlossaryWhat Is a Unified Namespace (UNS)?
One real-time source of truth for all operational data - how a UNS is structured with MQTT and Sparkplug B, and how it differs from point-to-point SCADA.
Read → GlossaryWhat Is an MQTT Broker?
The central hub of MQTT publish/subscribe messaging - QoS, Sparkplug B, and why brokers underpin cloud SCADA and IIoT.
Read → GlossaryWhen should you use HART burst mode?
Enable it for a real data-rate need on a point-to-point loop, publish only what you need, and confirm the host can still manage the device.
Read → GlossaryWired HART vs WirelessHART: how to choose
A selection guide on how criticality, update rate, power, and cable cost decide between wired HART and WirelessHART.
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