The compile error occurs because AOI's causing the compile error in the .ACD file have a signature applied, and there is a signature mis-match when the project is compiled.
The usual unexpected cause of this error is changing the major version of the Logix project offline. Sometimes, but not always, this messes up the signature checking.
Applying an AOI signature is used to monitor for user changes to the AOI definition. Make a change to the AOI, signature no longer matches. This is obviously important for safety applications.
The anomaly here is the major version change can cause having to create a new signature, when no user changes have been made to the AOI, while a user change always requires a new signature.
So if a signed AOI has a different signature than the original, either:
1. If the major version is different than the original, the AOI signature may have been affected by the version change, or there has been a user change. Best way to check is to use the Logix Compare Tool to determine if there are any differences in the affected AOI's Definitions between the original and current instances.
2. If the major version is the same as the original, then there has been a user change. To find what was changed use the Logix Compare Tool.
To fix the compile error:
For both of the above cases, open the AOI Definition and delete the existing AOI signature and then reapply the signature to generate a new signature.
If the AOI has been source protected, then the source protection key has to be present on the computer to allow unlocking the AOI to delete and apply the signature.
Changing a Safety AOI's signature in a safety application has implications for operation, liability and documentation, as that signals something has been changed.
