I'm not software so I may be wrong here, but first see the table on p12 of this:
http://www.usfirst.org/sites/default...ystem_RevA.pdf
In 2011 you would have used the slot number, 2012 you would use the number of that module (i.e.DSC1 or DSC2) If this hasn't been changed then your code would be trying to address a fourth DSC, which doesn't exist.