Modbus
Modbus — Universal serial (RTU/RS-485) and Ethernet (TCP/MBAP, port 502) SCADA communication protocol for PLCs, RTUs, sensors, and industrial field devices.
Modbus Parity and Character Format
Modbus parity and character format: data bits, parity, and stop bits for RTU and ASCII, the even-parity default, the two-stop-bit rule, and what parity misses.
Modbus Unit Identifier Explained: Unit ID by Scenario
Modbus Unit Identifier (Unit ID) explained by scenario: direct TCP devices, RTU gateways, multi-port gateways. Value ranges, common defaults, troubleshooting.
Modbus Broadcast Function Codes: Address 0 Explained
Modbus broadcast on address 0: which function codes support it, how serial and TCP differ, turnaround timing, gateway behavior, and when to actually use it.
Modbus Client-Server vs Master-Slave Terminology
Modbus client-server vs master-slave: the 2020 terminology change explained. What stays the same, translation table, and how to read mixed-terminology docs.
Modbus TCP MBAP Header Explained: 7 Bytes Byte by Byte
Modbus TCP MBAP header decoded byte by byte: Transaction ID, Protocol ID, Length, and Unit ID, with a real hex dump, network byte order, and common mistakes.
Modbus TCP Security Explained: TLS on Port 802
Modbus TCP Security explained: TLS on port 802, X.509 certificates, role-based access control, deployment alongside port 502, cipher suites, real setup.
Modbus Byte Order and Word Order: Fix Your 32-Bit Values
Modbus byte order and word order decoded: ABCD, CDAB, BADC, and DCBA. Fix reversed floats and byte-swapped longs, with a five-minute test and vendor defaults.
Modbus Exception Codes Explained: Complete Reference
Modbus exception codes 01 through 0B in full: Illegal Function, Illegal Data Address, Slave Device Failure, and gateway errors, each with the fix that works.
Modbus Register Map Explained: How to Read Any Device
Modbus register map reading made reliable: the four register types, the zero-based offset trap, data types inside registers, byte order, and scale factors.
Modbus Function Codes Explained with Real Examples
Modbus function codes with real hex frames: FC 01 to 06, FC 15 and 16, FC 23 and 43, plus register type matching and the mistakes that cause exceptions.
Modbus Security Risks and How to Protect Your Network
Modbus security risks in practice: why the protocol has no authentication, real attack techniques on RTU and TCP, plus segmentation, firewalls, and monitoring.
How to Configure Modbus RTU Over RS-485: Step-by-Step
Modbus RTU over RS-485 configured step by step: bus wiring and topology, termination and biasing, addressing, register types, and T1.5 and T3.5 timing.
Modbus TCP/IP Setup: Step-by-Step Configuration Guide
Modbus TCP/IP setup from scratch: IP planning, server and client configuration, MBAP header basics, gateway bridging to RTU, and connection troubleshooting.
Modbus Data Types: Decode Register Values Correctly
Modbus data types explained: UINT16, INT16, hex, binary, ASCII, 32-bit integers, IEEE-754 floats, and bitmasks, plus how to pick the right format every time.
Modbus TCP/IP Explained: Complete Beginner-to-Expert Guide
Modbus TCP/IP explained from the ground up: ADU structure, encapsulation across network layers, big-endian data, the client-server model, and function codes.
Modbus TCP Port 502: Setup, Security, Troubleshooting
Modbus TCP port 502 in depth: IANA registration, connection lifecycle, client limits, firewall rules, Wireshark filters, and the TLS secure variant on port 802.
Modbus RTU to Modbus TCP: Gateway Setup and Conversion
Modbus RTU to Modbus TCP conversion step by step: frame translation byte by byte, hardware and software gateway setup, Unit ID mapping, and timeout tuning.
Modbus RTU vs Modbus TCP: Frames and Key Differences
Modbus RTU vs Modbus TCP compared field by field: frame structure, CRC versus MBAP header, addressing, performance, and migrating serial devices to Ethernet.
Modbus Protocol Explained: RTU, TCP, ASCII, and Frames
Modbus protocol explained end to end: RTU, TCP, and ASCII variants, frame structure, function codes, master-slave architecture, and field troubleshooting.