When communicating from a remote PLC to a master PLC using the DirectNet protocol the master PLC is reading incorrect data. The 16-bit word being read is showing alarms that are not occuring at the remote PLC.

PLC using the DirectNet protocol the master PLC is reading incorrect data. The 16-bit word being read is showing alarms that are not occuring at the remote PLC. This word should be protected by error checking when corrupted data is being read by the PLC. Automation direct technical support has advised to download their most recent firmware. If anyone has experienced similar problems with the Automation Direct DL-06 PLC, please respond.

 

You can try switching to MODBUS. DirectNET only has a 8 bit LRC. MODBUS has a 16 bit CRC, which is much more reliable at error checking.

If you are still getting erroneous data, the problem most likely lies in the code or process.

 

I have had D0-05 plc slave outright lie when using direct net over radio modems. they don't do it with a wire. I considered trying modbus, but I have not had time to try. the LRC should find errors in the data, BUT IT WILL NOT CATCH A SLAVE RESPONDING TO THE WRONG REQUEST. In my case a request for data from a non-existent slave was ansnwerd buy one with an adjacent address, and the master took the data and used it as though it came from the correct slave.

When communicating from a remote PLC to a master PLC using the DirectNet protocol the master PLC is reading incorrect data. The 16-bit word being read is showing alarms that are not occuring at the remote PLC.