Modbus, DNP3, OPC UA, MQTT, EtherNet/IP, PROFIBUS, HART, BACnet and other fieldbus and network protocols. 127 terms in this topic - each defined in plain English on its own page.
Modbus, DNP3, OPC UA, MQTT, EtherNet/IP, PROFIBUS, HART, BACnet and other fieldbus and network protocols.
The 253-byte PDU ceiling that caps a read at 125 registers or 2000 coils, and why drivers split large maps.
Read → GlossaryHow a flow computer packs an IEEE-754 float into two 16-bit registers, why it reads as garbage, and how to verify it.
Read → GlossaryPer-application certificates and trust lists drive OPC UA mutual authentication, the rejected folder, and expiry risk.
Read → GlossaryThe open building-automation protocol - objects, services, BACnet/IP vs MS/TP, and bringing facility data into SCADA.
Read → GlossaryA write to slave address 0 reaches every device on a serial line with no reply - useful, but silent and unverifiable.
Read → GlossarySwapping the paper chart on a circular recorder, marking date and pens, and preparing it for integration.
Read → GlossaryThe mechanical instrument that traces static, differential, and temperature pens on a rotating paper chart.
Read → GlossaryClean vs persistent decides whether the broker keeps a client's subscriptions and queues messages while it is offline.
Read → GlossaryReconcile the register map, resolve the 40001 off-by-one, match the function code, and handle span-crossing reads.
Read → GlossaryHow SPC control limits differ from spec and alarm limits, and how pattern rules flag out-of-control processes.
Read → GlossaryRunning the PID loop inside a Foundation Fieldbus transmitter or positioner instead of the controller.
Read → GlossaryA reply that fails its checksum and is discarded as corrupt - pointing to line noise, not a dead device.
Read → GlossaryThe master acknowledgment that lets an outstation safely clear reported events, and why missing confirms lose or duplicate data.
Read → GlossaryDNP3's static Class 0 versus event Class 1/2/3 data model and how class polls differ from the integrity poll.
Read → GlossaryThe full outstation reboot, the Device Restart IIN bit it raises, and how a master re-initializes to avoid stale data.
Read → GlossaryIIN1.5 local control means a point is in hand mode and rejects remote commands; IIN1.6 device trouble is a device-specific fault.
Read → GlossaryThe fixed queue where a DNP3 outstation stores Class 1/2/3 events, plus overflow, the IIN buffer bit, and RBE.
Read → GlossaryIIN2.3 means the outstation dropped events because the master polled too slowly, leaving a real historian gap on a healthy link.
Read → GlossaryThe link-layer source and destination addresses that identify DNP3 devices, how they differ from IP, and why a mismatch silently drops the poll.
Read → GlossaryIIN1.4 means the outstation clock is untrusted; the master clears it by writing Object 50 so event timestamps stay accurate.
Read → GlossaryHow DNP3 organizes data by group and variation, and why the choice controls a pipeline outstation's poll bandwidth.
Read → GlossaryThe 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 → GlossaryAllow Modbus and DNP3 reads while blocking writes mid-stream, so a firewall permits monitoring but stops control.
Read → GlossaryReading past the TCP header into Modbus, DNP3 and EtherNet/IP payloads to see function codes and setpoint changes.
Read → GlossaryThe CIP-based industrial Ethernet behind Allen-Bradley controllers - messaging types and reading tags into cloud SCADA.
Read → GlossaryThe MEI type 14 read that returns vendor name, product code, and firmware revision so tools can auto-detect a device.
Read → GlossaryThe junction block connecting spurs to the trunk with per-spur fault protection, so one bad device cannot kill the segment.
Read → GlossaryThe device that feeds DC to an H1 segment without shorting out the digital signal on the same pair.
Read → GlossaryThe H1 trunk-and-spur cable that powers and talks to many field devices on one shared bus.
Read → GlossaryThe RC network at each end of an H1 segment that absorbs the signal so it does not reflect and distort.
Read → GlossaryThe Fieldbus Intrinsically Safe Concept: a simplified way to run a safe fieldbus segment with more devices.
Read → GlossaryDiagnose in order: wrong unit ID, offline device, blocked port 502, poll-timing tuning, and gateway remaps.
Read → GlossaryDiagnose byte and word order, floats split across two registers, signed vs unsigned, and scaling factor errors.
Read → GlossaryThe all-digital process bus for refineries and gas plants - H1, HSE, control-in-the-field, and its path to SCADA.
Read → GlossaryFC06 writes one holding register, FC16 writes a block atomically - why 32-bit values need FC16 and how to choose.
Read → GlossaryHow a serial-to-TCP gateway maps RS-485 slave addresses behind one IP and routes a poll to the right RTU.
Read → GlossaryPublish mode where a HART device continuously broadcasts its variables without being polled, updating faster.
Read → GlossaryHow a digital signal rides on the same 4-20 mA wires as the analog reading, plus point-to-point vs multidrop.
Read → GlossaryThe mode that puts many transmitters on one pair by fixing their current and going digital-only.
Read → GlossaryThe panel device that pulls digital HART data off many 4-20 mA loops for asset management.
Read → GlossaryHow smart digital signals ride on 4-20 mA loops, WirelessHART, and getting stranded instrument diagnostics into SCADA.
Read → GlossaryA device that regenerates a weak HART digital signal on long or high-capacitance cable runs.
Read → GlossaryA converter that splits a multivariable transmitter's extra HART variables into separate 4-20 mA outputs.
Read → GlossaryHART commands and multivariable digital data carried over Ethernet, the uplink from WirelessHART gateways and multiplexers.
Read → GlossaryIS barriers and isolators for Zone 0/1 devices versus non-incendive Division 2 modules mounted in the field.
Read → GlossarySet the connection and unit ID, map coils and registers with the right function code, then fix word order and scaling.
Read → GlossaryThe TCP/IP telecontrol protocol behind utility SCADA - ASDUs, cause of transmission, and how -104 data integrates.
Read → GlossaryThe digital-substation standard - logical nodes, MMS, GOOSE, and Sampled Values, and how its data reaches SCADA.
Read → GlossaryHow digitized CT and VT streams replace copper wiring on the substation process bus.
Read → GlossaryTwo status bytes in every DNP3 response - restart, need-time, events available, buffer overflow - that a master acts on.
Read → GlossaryThe IEC 62439-2 ring standard common in Profinet, where a manager heals a single break in about 200 ms.
Read → GlossaryAliases shrink NDATA payloads for cellular links; the rolling seq number detects missed messages and triggers a rebirth.
Read → GlossaryDecode responses 01, 02, 03, 04 to tell whether the map is wrong, the register is missing, or the device has faulted.
Read → GlossaryHow input registers differ from holding registers in a vendor map, and setting the correct read function per tag.
Read → GlossaryThe verb in every Modbus request - codes 01 to 16 - which reads a sensor, which writes a command, and why a wrong code fails.
Read → GlossaryException 03 means your value is out of range, not a bad address. Causes, how to isolate it, and how it differs from 02.
Read → GlossaryException 01 means the slave does not support the function code you sent. Common triggers and a decision path to fix it.
Read → GlossaryException 02 means the polled register does not exist - a pinpoint addressing bug, not a dead link.
Read → GlossaryModicon's legacy 1 Mbit/s token-passing peer-to-peer network, distinct from Modbus RTU and TCP, that needs a gateway.
Read → GlossaryWhy 40001 is really offset 0 with function code 03, where the off-by-one comes from, and how to align a vendor map.
Read → GlossaryThe four Modbus tables - coils, discrete inputs, input and holding registers - what's read-only vs read-write, and mapping.
Read → GlossaryThe 3.5-character silent interval and transmit turnaround, and how to tune the wait on slow radios and RS-485 links.
Read → GlossaryHow signed and unsigned counters span two registers, the four decode permutations, and picking the right one.
Read → GlossaryBinary RTU over RS-485 with a CRC vs Modbus TCP over Ethernet with an MBAP header, and how a gateway bridges them.
Read → GlossaryThe no-reply fault on a Modbus link, its usual causes, and how retries turn it into a comms-fail alarm.
Read → GlossaryThe RS-485 slave address vs the Modbus TCP Unit ID, and how a gateway routes one IP to many chained field devices.
Read → GlossaryThe gap between the zero-based wire address and one-based documentation numbering, and the per-device base fix.
Read → GlossaryA broker-to-broker link that forwards selected topics from a site broker up to a cloud broker.
Read → GlossaryThe MQTT 5 cap on unacknowledged in-flight messages that provides backpressure so a slow gateway is not flooded.
Read → GlossaryHow 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 → GlossaryQoS 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 → GlossaryHow 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 → GlossaryThe MQTT 5 timer and flag governing how long the broker holds queued messages for a flapping gateway.
Read → GlossaryA $share group that load-balances one topic stream across several consumers, one message each.
Read → GlossaryAn MQTT 5.0 shorthand that replaces a long topic with a small integer to cut per-message bytes.
Read → GlossaryHow 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 → GlossaryAn MQTT 5.0 grace period that holds the Last Will so a quick reconnect avoids a false offline event.
Read → GlossaryNBIRTH publishes an edge node's full metric set on connect; NDEATH, set as the MQTT last will, signals it has died.
Read → GlossaryThe data-free DNP3 message that carries only status flags to prove a link is alive and signal outstation restarts.
Read → GlossaryThe open standard linking EV chargers to a central management system, carrying status, meter values, and remote control.
Read → GlossaryThe interoperability standard of automation - why DCOM held OPC Classic back and how OPC UA's model changed integration.
Read → GlossaryDecoding good, uncertain, and bad plus substatus like last usable value, sensor failure, and comm failure.
Read → GlossaryTunneling software that carries OPC data across networks and firewalls over a single TCP connection, replacing fragile DCOM.
Read → GlossaryHow 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 → GlossaryThe 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 → GlossaryThe 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 → GlossaryClient-server sessions and monitored items versus PubSub publishing UADP or JSON over UDP or MQTT for one-to-many telemetry.
Read → GlossaryHow push-style delivery uses sampling interval, publishing interval, and deadband to send only changed values, saving bandwidth versus constant polling.
Read → GlossaryConverting request/response OPC UA into publish/subscribe MQTT at the edge, mapping node IDs to topics and Sparkplug metrics.
Read → GlossaryPiping OPC UA subscription updates into SQL tables with mapping, batching, quality preservation, and store-and-forward buffering.
Read → GlossaryAssigning unique IDs per unit and aggregating to cases and pallets to build full track-and-trace genealogy.
Read → GlossaryThe classic industrial fieldbus - DP for discrete control, PA for process instruments - and how its field data reaches modern SCADA.
Read → GlossaryFast RS-485 DP for discrete I/O versus slow two-wire bus-powered PA for process instruments, bridged by a coupler.
Read → GlossaryReal-time industrial Ethernet from PI - RT and IRT explained, and how PROFINET plants connect to SCADA and the cloud.
Read → GlossaryCertified capability tiers that define whether a Profinet device offers topology discovery, diagnostics or full IRT.
Read → GlossaryPrioritised Real-Time Ethernet frames versus hardware-scheduled Isochronous Real-Time with sub-microsecond jitter for motion.
Read → GlossaryThe device that translates one industrial protocol or signal into another so mismatched field equipment and SCADA can exchange data.
Read → GlossaryThe translators that bridge Modbus, PROFIBUS, HART, and OPC UA so mixed-vintage devices reach modern cloud SCADA.
Read → GlossaryConverting many field protocols into one consistent tag model and payload before publishing upstream.
Read → GlossaryA deny-by-default posture that allows only the protocols a segment needs, turning any unexpected one into an alert.
Read → GlossaryA lost PUBACK makes the publisher resend with the DUP flag - at-least-once delivery means consumers must be idempotent.
Read → GlossaryA multi-axis polar chart that turns several related variables into a shape signature to compare.
Read → GlossaryIEEE 802.1w loop prevention that blocks redundant links and reconverges in seconds using BPDUs and root bridges.
Read → GlossaryWhy a 32-bit Modbus float reads as garbage until word and byte order are set to match the device.
Read → GlossaryHow to read the vendor address table - address, type, data type, scaling, access - and build a working poll from it.
Read → GlossaryThe single-ended point-to-point serial standard wired between RTUs, radios, and flow computers.
Read → GlossaryThe differential serial standard behind Modbus RTU and PROFIBUS - multidrop wiring, RS-232 vs RS-485, and serial in SCADA.
Read → GlossaryWrapping cleartext Modbus or DNP3 in an encrypted tunnel for confidentiality and integrity, without touching the endpoints.
Read → GlossaryDNP3's two-step arm-then-fire control handshake, its select timeout window, and how it differs from direct-operate.
Read → GlossaryThe IEC 61131-3 language that lays a process out as ordered steps and transitions - ideal for sequences.
Read → GlossaryThe multiport appliance that puts legacy serial RTUs and meters on an IP network via virtual COM ports or raw TCP.
Read → GlossaryHardware RTS/CTS vs software XON/XOFF handshaking, and RTS keying of a serial radio transmitter.
Read → GlossaryThe 8N1 and 8E1 shorthand for data bits, parity, and stop bits, and how they catch line errors.
Read → GlossaryThe device server that puts legacy RS-232/RS-485 gear on an IP network - raw TCP vs virtual COM, explained.
Read → GlossaryThe MQTT specification that makes IIoT data SCADA-ready - birth/death certificates, report-by-exception, and unified namespace.
Read → GlossaryThe command messages that push setpoints and control writes down to an edge node or a device behind it.
Read → GlossaryHow one gateway (the edge node) fans out to many devices via the group/node/device topic hierarchy.
Read → GlossaryThe consuming host edge nodes watch via STATE - losing it, not the broker, triggers store-and-forward.
Read → GlossaryA host writing Node Control/Rebirth to make a stalled edge node re-emit its full birth certificate.
Read → GlossaryThe trunk is the shared home-run backbone; spurs are the short drops to devices, each with its own rules.
Read → GlossaryNavigating an OPC server's address space to discover available nodes before subscribing, and how tools use it to map tags.
Read → GlossaryMultimeter and scope procedure: verify A/B polarity, idle bias, 120-ohm termination, daisy chain, and node faults.
Read → GlossaryFind the real trigger: keep-alive firing NDEATH, sequence gaps, duplicate client IDs, or QoS and session settings.
Read → GlossaryA long-lived pre-shared update key protects short-lived session keys that rotate often to shrink the blast radius.
Read → GlossaryOne 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 → GlossaryThe central hub of MQTT publish/subscribe messaging - QoS, Sparkplug B, and why brokers underpin cloud SCADA and IIoT.
Read → GlossaryThe IEC 62591 self-healing 2.4 GHz mesh that adds field monitoring without pulling wire.
Read →Merobix is cloud SCADA for oil & gas - it reads the instruments and protocols defined here into one dashboard.
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