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Modbus RTU vs Modbus TCP

The serial (RTU) and Ethernet (TCP) variants of classic Modbus; compared by physical layer, speed, distance and integration.

Updated: 2026-07-06
Technical ComparisonSeriModbus RTUEthernetModbus TCP
Physical layerRS-485 / RS-232 serialEthernet (TCP/IP)
SpeedLow (kbps)High (Mbps+)
TopologyDaisy-chain (bus)Star / switch-based
SeriModbus RTU
Pros
  • Simple and robust over RS-485
  • Long distance (hundreds of meters)
  • Cheap on the device side
Cons
  • Low speed, single master
  • Needs care with addressing/termination
EthernetModbus TCP
Pros
  • High speed, standard Ethernet
  • Multiple clients, easy integration
  • Fits SCADA/IT networks
Cons
  • Requires Ethernet infrastructure and switches
  • Weak deterministic real-time guarantee

Verdict

For simple, long-distance and economical field connections, Modbus RTU is still reliable. For high speed, multiple clients and SCADA/IT integration, choose Modbus TCP. The two can also coexist via a gateway.

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