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Kepware Knowledge Base: Solution

Siemens Device Returning Protocol Error [Class=0x81, Code=0x04]

Last Update: 11/7/2018
The Event Log displays the error message, "Unable to read # bytes starting at offset 0 for <requested tag> on device <channel.device>. Device returned protocol error [Class=0x81, Code=0x04]."

Possible Cause:
The controller's Protection settings are directly related to protocol error [Class=0x81, Code=0x04]. If the Protection settings match the "Access Level" and "Permit access with PUT/GET communication from remote partner" options specified in the Siemens TCP/IP Ethernet Driver product manual, then the controller's memory (that is, the SIMATIC memory card) may need to be reset.

Reset the controller's memory and then download the S7 project. At that point, the Siemens TCP/IP Ethernet Driver should be able to access the controller's memory.

For more information, refer to "How To Configure S7-1500 Connections" in the Siemens TCP/IP Ethernet Driver product manual.