Could you tell us some more about your usecase why and when do you need such function? At the moment there is no solutions for keeping the IO output values alive over the complete download cycle. You would need to use the online change for that.
As a workaround you could use PLC system events to save your actual IO data to a retain variable e.g. PrepareStop and then use another system event e.g. PrepareStart to restore it. Beware that here a short time with IOs getting to FALSE cannot be avoided.
ctrlX PLC Engineering system events
Please also beware that there is a function called substitute for keeping IO values in actual state when fieldbus goes down to INIT. This is available for the S20-DO, but not for ctrlX IO XI2... (only fix fallback value). Substitute is also available for analog outputs S20 / ctrlX IO. See S20 documentation here.
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