local - remote switch to select which HMI can write to setpoints in the PLC

I have a panel in front of the equipment with a PanelViewPlus 7 standard with Factory Talk ME and a Factory Talk SE HMI up in the control room.

When the local-remote switch at the equipment is in Local the SE HMI should not be able to write to any setpoints in the PLC (1756-L73).

When the local-remote switch at the equipment is in Remote the SE HMI can write to the setpoint tags. maybe the ME HMI can't write to the setpoints in Remote but I am less concerned with locking out the local touchscreen HMI in Remote. Mainly I want to lock out writing from the SE HMI when the machine is in Local.

The catch is the program is using the Rockwell Process Library Plant Pax blocks P_Din, P_Dout, P_Ain, P_Aout so a single tag of AOI type has all the members for enabling and disabling alarms, setting CVs to manual override, changing targets and setpoints, etc.

I could build the SE and ME HMIs to read and write different AOI tags and then select the appropriate tags in the program based on the local/remote switch, but that would be another instance of a plant pax block with a hundred parameters for each IO point which seems like a pretty verbose and heavyweight solution, although relatively straightforward and easy for anyone to understand.

Maybe there is some trickery that can be performed by changing the Cfg_Area parameter in the Plant PAX blocks. It is a local block tag but with external access read/write. Then through some other Factory talk trickery only user logged in from the ME terminal has permission to write to the tags when they are part of the "local" area.

It also looks like Factory Talk Security can be configured in RSLogix, so I could prevent tag values from being modified through a permission set, but I'm not sure how I would change the permission set to exclude one HMI terminal or the other based on the local/remote switch.

Any suggestions on the most straightforward way to accomplish this would be appreciated.

Visibility of any objects that can write to the PLC based on the selector switch position?

thanks for the suggestion steve. I am trying not to modify Rockwell's Plant PAX AOI's in the PLC or the faceplates on the HMI.


The buttons and entry fields on the HMI that write to the PLC are part of the faceplates and are disabled if the user doesn't have the right security privileges. The security privileges are assigned by groups that correspond to areas. each plant pax AOI is configured to be part of an area. the user must be part of the group for the area that has enough security privileges (assigned by a letter A..H) in order to press the button or input the new setpoint.


The security privileges tags (eg Security\EnterOperSettings = "ABCDE") are however memory tags in the HMI. Maybe I can overwrite them so there are no privileges when the switch is in Local.


definitely way more complicated that I like

it seems like a need to programmatically add and remove security codes from a group based on a discrete input but this is not possible:


FactoryTalk View SE: Change runtime security code assignments on the fly 790953 | Date Created: 04/04/2016 | Last Updated: 01/12/2018
Access Level: Everyone




Question

Can I change runtime security code assignments on the fly?
Answer

No






I think changing the area of all of the plant pax blocks so the user doesn't have permissions might cause problems with all of the alarms built in to the plant pax blocks changing from one area to another.


Maybe a see through light grey semi transparent square on top of any control elements that is visible and intercepts any clicks when the Local DI is asserted.


Seems like it really ought to be done in the PLC program by rejecting inputs from the remote HMI if it is in local. Which means I have to have to sets of plant pax blocks.