Modbus is a communication protocol for exchanging values between industrial devices. It is simple and openly published, so it interoperates widely across vendors.
Request a required value
Check the register map
Return register values
Modbus is a communication protocol for exchanging values between industrial devices. It is simple and openly published, so it interoperates widely across vendors.
Modbus dates from 1979 and is still the most widely deployed industrial protocol, because it is simple to implement and vendor-neutral.
It works as request and response: an upstream device asks for the value at an address and the device answers. It comes as Modbus RTU over serial links and Modbus TCP over Ethernet.
Its limits are equally clear. Values carry no name or unit, so a human must know from documentation what register 40001 means. There is no security either. Newer protocols such as OPC UA address this, but a large share of installed equipment still speaks Modbus.
RTU runs on a serial link such as RS-485; TCP runs over Ethernet. The data model is nearly identical and only the transport differs. Keeping existing RS-485 wiring and converting to TCP at a gateway is a common arrangement.
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What IYULAB provides in this area.
Questions that come up when evaluating Modbus.
The vendor's communication manual carries it. Failing that, changing values while observing with the equipment owner is the practical method.
The protocol has no authentication or encryption. The standard mitigation is separating the control network from the office network and placing the devices behind a gateway.
Modbus RTU supports multiple devices on one RS-485 line. As device count rises, response time grows, so plan it against your polling interval.
A look at your equipment and current workflow is usually enough to scope it.
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