Why can't I login to my user account when using cMT Viewer?


When using a cMT or cMT X series HMI, the “Security” control address must be assigned to a PLW register if a remote user will log into the HMI’s user accounts via cMT Viewer. Within this post, we demonstrate how to set the UAC control address if user login does not appear to function.
Note: This situation may arise when migrating from a non-cMT to a cMT or cMT X HMI.

Software Version:

EasyBuilder Pro

Related Tutorials:

Remote Viewer Comparison
Video - A comparison between cMT-Viewer and VNC
Video - cMT Viewer vs. VNC Viewer + New cMT3072 Demo Project


  1. When starting a new EasyBuilder Pro project for a cMT/cMT X series HMI, UAC control functions are configured as PLW registers by default. You can confirm this in the “Security” tab of the “System Parameter Settings”. Selecting the “Usage…” hyperlink will reveal the project’s current UAC control function register mapping:
    Note: When migrating a project from a non-cMT series HMI to a cMT series HMI, the UAC control function will remain mapped to LW registers. You must manually re-map the “Control” register to PLW memory in order to login to a user account with cMT Viewer.

  2. The UAC control register mapping can be changed from LW to PLW by selecting the “Address” drop-down list:

cMT Viewer examples:

When using UAC control functions mapped to PLW registers to log in, you can see the login was successful in the “PLW-10754: current user name” register:

When using UAC control functions mapped to LW registers, you can see that the login attempt was not successful as the “PLW-10754: current user name” register remains blank:


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