ARServerModbus TCP Learning
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Modbus TCP basics

Modbus TCP is the practical language many HMI and SCADA tools already understand.

For ARServer users, Modbus TCP is a consumption interface. It does not replace IEC 61850; it makes selected relay values easier for classic HMI, SCADA, DCS, and test clients to poll.

Classic output

What Modbus TCP means in an ARServer workflow

Modbus TCP is simple by design. A client polls a server for bits and registers. This simplicity is why many HMI and SCADA packages can consume Modbus data even when they do not speak IEC 61850 directly.

Main data areas

  • Coils: writable Boolean outputs in traditional Modbus terminology.
  • Discrete inputs: read-only Boolean status points.
  • Input registers: read-only numeric values.
  • Holding registers: numeric registers that are often used for configurable or writable data in many systems.

Why address planning matters

Unlike IEC 61850, Modbus does not carry rich names such as XCBR1.Pos.stVal. The meaning of address 30001 comes from the mapping document. A good gateway must keep the register map deterministic, stable, and easy to hand over.

ARServer principle: map only selected and validated IEC 61850 points. Keep the Modbus register map small enough to audit and stable enough for HMI engineering.

What HMI engineers need

HMI and SCADA users need address, type, scale, meaning, quality behavior, and stale behavior. If those are not documented, a register can show a value while hiding that the upstream relay communication is broken.

IEC 61850 to ModbusLearn how ARServer bridges named relay values into Modbus points.Validation MatrixUse a checklist before handing a register map to HMI users.