The ModbusAsyncDevice is a component, which is responsible for servicing a physical device connected to the Modbus network. The AAC20 device acts as a Modbus master to all other Modbus devices on the attached RS485 port. Each device is represented by a Modbus device and has a unique Modbus address (1 to 247) as well as other Modbus config data and starting addresses for Modbus data items (coils, inputs, input registers, holding registers). The component has a Ping action available under the right-click, which sends a test message to the device to check the device status. Each ModbusAsyncDevice has a Ping Address container slot with 3 properties slots (Address Format, Ping Address Reg, Ping Type). These properties specify a particular data address (either input register or holding register) to use as the device status test (meaning Monitor ping requests). Ping requests are generated at the network-level by the configurable network monitor (ModbusNetwork -> Ping Enabled). If enabled, a network’s monitor periodically pings (queries) this address. If any response from the device is received, including an exception response, this is considered a proof of communication, and the Modbus client device is no longer considered down if it was previously marked so.
The ModbusAsyncDevice component has the following slots:
- Status: Device’s actual status (read-only);
- Available options: OK (device is working properly), Disable (device is disabled, the Enable slot is in false), Down (device is not available), Ok, some points down/error (error in points reading), Network disabled (Modbus network is disabled);
- Fault Cause: fault cause description;
- Fault Status: device error status (true: device communication error);
- Enable: enables/disables the device;
- Device Address: Modbus device physical address (0: network broadcast address, 1-248 addressing range);
- Timeout: max. device response time from the device request;
- Inter Message Delay: time between messages sent to the device;
- Retry Count: max. number of error messages (CRC error, lost messages);
- Address Format: Modbus address format (Modbus, decimal);
- Ping Address Reg: input or Holding type register’s number, which will be read for device connection test;
- Ping Type: tested register type: Input/Holding;
- Byte Order: byte reading order, for 32-bit: 3210 (Big endian), 1032 (Little endian).