So you are saying that the HMI will read and write to the same tag in the PLC? I havn't been able to see an option in the standard settings that would allow me to set a different tag for reading, unless I write my own code for the switch.
Yes, the tag can be read and write. The built in three state toggle will use a single integer tag for both read and write. The tag property will be read and write by default, but could be changed to read or write only (which would defeat your purpose). I mention that in case you are using an existing tag and have problems.
You set the values for each position on the Advanced tab. If the PLC writes an undefined value, the appearance will go to the default state you choose. The appearance should follow the value of the tag so the PLC can change it. And as keshik said, when you perform an action by touching the button on the screen, the HMI will only write the value once. Afterward, the PLC could change it to a different value and the graphic object will reflect that change.
You can set it up to write to a separate tag if you make the control action "User Defined", but I am pretty sure that you don't need to mess with that. This is what is great about Crimson 3.0, It will do what you would naturally expect it to do with very little hassle 99% of the time.
If you want to make the switch do something totally off the wall or perform multiple actions, you might then need to use the User Defined switch settings and then put your own logic in the Advanced Tab for each section of the switch as it's "touch" action.
I would like to use Crimsons3 3 state toggle HOA switch on a G310 to set the mode in a Micrologix1400.
Set the mode of what? I don't believe it is possible to set the RUN/REMOTE/PROGRAM mode of the PLC, but I would be willing to be proved wrong.
If you are talking about the mode of some user programmed machine in your PLC logic by altering the value of a regular old integer, then you should not have any problem.