Networking

Modbus RTU

Definition

Serial Modbus, normally over RS-485, with binary messages, a CRC-16 check, and frames delimited by a silent interval of at least 3.5 character times.

One master, up to 247 addressed slaves, one transaction at a time. Most intermittent faults are physical: missing termination, missing bias, no signal common, or cable routed beside drive output conductors.

Modbus RTUSerial Modbus over RS-485: function codes, register addressing, the off-by-one that catches everyone, and the physical layer details that decide whether a bus is stable.

Modbus RTU

Definition

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See also