Modbus

The Modbus tab configures Modbus TCP and Modbus RTU. Depending on the application, both sections can operate as a master or slave, or can be disabled.

Modbus TCP

Setting	Meaning
Mode	Disabled, Master (Client), or Slave (Server)
Slave port	TCP port for slave operation; default `502`
Slave Unit ID	Unit ID of IOZER basic in slave mode
Max. registers	Number of registers provided in slave mode
Multi-write	Permits write operations spanning multiple registers

In master mode, TCP connections are managed with a description, host, port, Unit ID, timeout, and retry count.

In slave mode, the Modbus TCP targets configured in datapoints are provided as holding registers. Register addresses are entered as zero-based values in IOZER basic. With Max. registers set to 100, the valid address range is therefore 0 through 99.

Modbus RTU

Setting	Meaning
Mode	Disabled, Master (Client), or Slave (Server)
Baud rate	Transmission rate on RS485
Data bits, parity, stop bits	Serial communication parameters
Slave Unit ID	Unit ID in slave mode
Max. registers	Number of registers provided
Multi-write	Permits write operations spanning multiple registers

In master mode, connected RTU slaves are managed by description and Unit ID. Registers to be read or written are assigned through the data sources and data targets of the datapoints.

Status

The Modbus status shows the interface, current status, most recent error, and most recent update. This view is especially important during commissioning and troubleshooting.

Modbus values are mapped to datapoints for use by local logic. Connection and RS485 information is available under Electrical connection.