Use of CF card
The particular site i visited did not have a final backup of AC800M plc. They had the CF card inserted in the plc slot. Using CF card reader i took the program. When i tried to go online with that backup, it gave a message saying that i need to download the program. After i downloaded the program, i found the final changes in the program saved and i didnt need to make any further changes.
Will the program backup taken from CF card always ask for a download or did i make any mistake.
Probably, the program in the controller did not matched the applicstion in the CF card. That may be the reason which prompted to download again.
It is best practise to "Download to Removable Media" after any changes are downloaded into the controller because incase this is not done then controller will boot oncase of power outage from CF card with what all application is present in the CF Card.
As long as Appliaction in Controller and CF Card is same, it should not.