Industrial Engineer · phase 5 of 16 · noun
Modbus TCP
Modbus application protocol transported over TCP/IP Ethernet.
The Explain card
- Plain English
- Modbus TCP is the same register model carried inside TCP packets on Ethernet. The serial address becomes a unit identifier, and any client can open a connection to any server.
- Example
- A SCADA server reads holding registers from a drive's Ethernet port and a PLC reads the same drive at the same time. Both are clients, and the drive answers each in turn.
- Why it matters
- It needs no special hardware and no vendor tools, which is why it is the fallback when two brands have to talk. It also has no security and no timing guarantees, so it belongs on supervisory data and never on anything that runs a machine.
- Hook
- Modbus, with the serial cable swapped for a switch.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
The commissioning laptop uses Modbus TCP to read the drive frequency command and verify the motor speed feedback.
Why these words
- Modbus English proprietary coinage from Modicon and bus identifies the protocol family
- TCP English initialism of Transmission Control Protocol identifies the communication method used by this member of the family
Where it came from
- Origin
- English technical phrase combining Modbus, coined by Modicon in 1979, with the networking initialism TCP
- Entered the language
- 1999
- What changed
- Modbus first named a serial industrial protocol family, then the added TCP label distinguished its Ethernet-oriented form.
How it is spelled
- Pattern
- Modbus keeps an initial capital followed by lowercase letters
- Pattern
- TCP remains fully capitalized because it is an initialism
- Pattern
- The two elements are separated by a space
- Breaks the pattern
- The spellings MODBUS TCP and Modbus TCP/IP also occur in technical documents.
Spelled like
- Modbus RTU
- Modbus ASCII
- OPC UA
Broken into chunks
-
Mod
- Modicon
- Modsoft
-
bus
- fieldbus
- PROFIBUS
-
TCP
- UDP
- IP
What it sits beside
Same subject
- Modbus RTU
- function code
- holding register
- unit identifier
- TCP port 502
Same shape
- OPC UA
- PROFINET IO
- Modbus ASCII
industrial Ethernet protocols
- Modbus TCP
- EtherNet/IP
- PROFINET
Modbus forms
- Modbus TCP
- Modbus RTU
- Modbus ASCII
Where it sits in the deck
Phase 5: PLC Industrial Communications
The protocols that let controllers, drives and operator panels talk, plus the addressing and description files that make them agree on what was said.
