This error is returned by several driver functions to show that the device does not communicate / does not have a connection to the fieldbus system.
In case of a Slave device, the Slave is not connected to a Master or the Master does not accept the Slave configuration.
In case of a Master device, there are either no Slaves connected or no Slave with a corresponding configuration is found on the fieldbus.
The COM-Flag on the Master is set if at least one Slave device could be correctly accessed.
NOTE: If this error is returned from xChannelIOWrite() or xChannelPLCActivateWrite()/xChannelPLCIsWriteReady() I/O data are successfully transmitted to the device and will be send on the next successful bus cycle.
NOTE: If this error is returned by xChannelIORead() or xChannelPLCIsReadReady() the input data will be read from the DPM containing old data or a data states, if supported and enabled by the fieldbus configuration.
Following Reasons may apply:
- Bus cable is not connected
- There is a configuration mismatch between master and slave(s)
- The bus is set to be started by the application. In this case xChannelBusState() can be used to enable the bus or to set the initial output data (see How do I set the initial output data?)