3.2 Modbus Slave – configuration dialog
3.2.1 Modbus TCP/IP Slave configuration
The configuration dialog is shown in Figure 3.3.
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.
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).
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