3.2 Modbus Slave – configuration dialog

3.2.1 Modbus TCP/IP Slave configuration

The configuration dialog is shown in Figure 3.3.


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Figure 3.3: Modbus TCP/IP Slave configuration dialog

The upper left part of the dialog contains Connection parameters. Namely:

Slave address
– Slave device address. There can be up to 255 Slave stations on same IP address. The address 255 is reserved for broadcast.
IP Address
– Defines the network adapter where the Slave is listening. Leave it blank for all network adapters or specify IP Address of a chosen one.
Port
– Port (TCP address) of the Slave station. The default port for Modbus is 502.
Timeout
– Not applicable for Modbus TCP/IP Slave configuration.
Reconnect
– Not applicable for Modbus TCP/IP Slave configuration.

3.2.2 Modbus RTU Slave configuration

The configuration dialog is shown in Figure 3.4.


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Figure 3.4: Modbus RTU Slave configuration dialog

The upper left part of the dialog contains Connection parameters. Namely:

Slave address
– Slave device address. There can be up to 32 Slave stations. The address 255 is reserved for broadcast.
Port
– The serial line used for communication. Usually COM* for Windows target devices or /dev/ttyS* for Linux target devices. Replace "*" symbol according to the chosen serial port!
Baud rate
– All stations on one bus must use the same baud rate. In bits per second.
Parity
– The error checking mechanism. All stations on one bus must use the same parity.
Stopbit
– Stop bits sent at the end of every character. All stations on one bus must use the same parity.
Timeout
– Not applicable for Modbus RTU Slave configuration.
Reconnect
– Not applicable for Modbus TCP/IP Slave configuration.
Sync. time
– Synchronization time. The Modbus protocol defines the frame end as silence on the line for a period equal to transmitting 3 characters. Use 0 to respect this timing. All nonzero values define the length of the frame end (in seconds).