I not found the new option OCDS Break Level in uVison2 (allows to execute interrupt functions, while system is stopped). This enhancement promoted in version 4.26, and only mentioned in release notes.
We had to take out this feature again from Version 4.27 since single stepping was not working correct. In the XC16x devices it seems to be impossible to allow background tasks while in break state. So I ask you to download the new V4.27.