Cannot Write to Holding Registers Using Modbus Custom Device When Running on Localhost

Updated May 31, 2021

Reported In


  • VeriStand


  • Modbus Custom Device

Issue Details

I am using the NI VeriStand Modbus Custom Device to perform Modbus communication, and am trying to write values to my holding registers in a project I am running on my local Windows computer (localhost). When I try to write a value to a holding register, the data is not actually written to the holding register. Reading from holding registers works correctly, and correctly returns data.


This issue was the result of a bug in the custom device that is fixed in the custom device's 2019 release. Updating to the 2019 release of the Modbus Custom Device will resolve the error.