Proface HMi - Incorrect Base Screen Displayed

I've added a few new Base Screens to an existing project on a Proface LT3300.

On random occasion (including power up) an incorrect Base Screen is displayed.

I've configure the initial Base Screen as "1", though on random occasions this screen isn't shown, rather one of the new Base Screens is displayed.

On other random occasions one of the new base screens is displayed and I can't switch to other screens.

I've used "Screen Switch" buttons and 99% of the time everything works fine, but once things have gone wrong I have to download to the HMI to get back to things working correctly again. (Power cycling does not fix).

I've had this problem manifest on actual HMI and Simulator.

I suspect the PLC is writing to a screen change request register, but believe I have this feature disabled in the system settings. There is no code that (intentionally) requests a screen change from the PLC - just operator driven switch screen buttons.

Any suggestions on how to debug gratefully appreciated.

Welcome
Check in the project window under display unit, system area you will find addresses used for control and indication functions, there should be a 'change to screen' with a word address against it, check through your PLC program to see if you are writing to this address.

Steve

Hi Steve,

I have "Enable System Data Area" unchecked (System Settings\Display\Display Unit\System Area). Therefore there is no address allocated to "Change to Screen" or any other of the System Data Area Items. This is why I believe I have screen change at PLC request disabled (as I require).

The problem is still manifesting. I've watched the HMI (with no operator input - just watching) and the displayed screen screen will just change after a random time - to any one of the base screens.

Very strange! - any further thoughts?

Glad to say this issue is resolved now, just posting an update so others suffering the same problem can make reference to this thread for an answer.

1. Existing program was indeed writing to "change to screen" control address
2. The check box "Enable System Data Area", works in a way I didn't expect. It does not disable control of the current screen from the PLC when unchecked, it just doesn't share data back to PLC related to screen control (such as current screen number). Quite confusing really as address which HMI will read from to execute PLC requested screen change will not be shown on the configuration screen if the checkbox is unchecked, but it will still use these address to control the screen at run time!