Modbus

Modbus is the open master and slave protocol that most inverters, meters, and battery systems use to expose their readings and accept commands as numbered registers.

Modbus RTU runs over serial lines; Modbus TCP runs over Ethernet on port 502. A client reads coils, discrete inputs, input registers, and holding registers by address, and writes to coils and holding registers. Each device publishes a register map naming the address, data type, scale factor, and unit of every value, and byte and word order must be configured per device. An energy management system is a Modbus client to the site’s devices and can also run a Modbus server to publish site data to SCADA.

Also called: Modbus TCP, Modbus RTU