Jay - Assume you've downloaded the relevant manuals from the dCS support page, if not worth doing:
http://www.dcsltd.co.uk/page/support
Given your configuration I'd make sure you were piped up according to PAGE 14 of the SCARLATTI UPSAMPLER manual (Yes...scarlatti....the Delius/Purcell manuals predate your type of setup)
You will need to set the Delius to act in Master mode, cf: the Delius manual on how to do this. This should push the Purcell to slave.
http://www.dcsltd.co.uk/page/support
Given your configuration I'd make sure you were piped up according to PAGE 14 of the SCARLATTI UPSAMPLER manual (Yes...scarlatti....the Delius/Purcell manuals predate your type of setup)
You will need to set the Delius to act in Master mode, cf: the Delius manual on how to do this. This should push the Purcell to slave.