Applicable Model(s)

HMI5000 Series
cMT Series


PLC No Response








If communications between the HMI and PLC are interrupted, a “PLC No Response” error message will appear on the HMI.  The following are steps that may help resolve the issue.


There are a number of things that can cause a PLC No Response error:


The communication cable may be wired incorrectly.

Solution: For serial communications, check cable wiring and test for continuity as well as any shorts between adjacent pins. Verify the cable using the Cable Assembly Instructions located in the Support Center in the Controller Cables section.

For Ethernet communication, check that you are using a crossover Ethernet cable for direct connections between devices or that all of your devices are connected through an Ethernet switch.


The protocol settings in System Parameters do not match the PLC communications parameters.

Solution: Download the corresponding Maple Systems controller information sheet from the Support Center in the Controller Info Sheets section. Go to Edit > System Parameters, then select the protocol from the Device List and click settings. Check these settings against the Controller Information Sheet and the PLC settings. If you are attempting to communicate over Ethernet, be sure that the devices are on the same subnet with unique IP addresses.  


The HMI is referencing a PLC address that is invalid or does not exist.

Solution: If an object is addressed to a register in the PLC and that object does not appear on the HMI, and you receive a “PLC No Response” message, then that register has not been found in the target device.

  • Check the addresses in the PLC to ensure the target register exists.
  • Create a test project with only one Numeric Object or Bit Lamp object configured for the address in question (or any address if all communications appears to be inoperable) and download that the HMI.

NOTE: The PLC No Response message will appear if the HMI has not received a response after the time specified in the Timeout parameter of the protocol (go to System Parameter Settings > Protocol Settings > Settings button to view the timeout parameter). Slow communications networks can prevent a response from the PLC from reaching the HMI within the time specified in the timeout parameter.

If the suggestions above do not resolve your PLC No Response error:

  • Check the controller user manual for the default settings.
  • Contact the controller manufacturer for help in determining the communications parameters.
  • Try different combinations of baud rate, data-bits, and parity.
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