Down Coverting to 15.5

Faisal,
 
With cadence tools you cannot downrev to major releases say 16.x to 15.x but you can downrev with in sub-release directly say from 16.3 to 16.2/16.0(file->export->save design to)
 
How I do from major release i.e 16.x to 15.x is
- extract the library from the design, use the downrev  command ( look in installation path Cadence\SPB_16.2\tools\pcb\bin)
- extract the netlist from the design using tools-->reports ( flow is to use Third party netlist import)
- export all elements from the design using subdrawing ( make sure you select all in find filter) - remember you need to select all options in OPTIONS  like preserve refdes, nets of shapes, nets of vias, testpoints
 
now open a new drawing file in 15.x
- Modify your library path to extracted library path in above steps
- import the third party netlist exported in above step
- import the subdrawing  exported
 
you can also export the constraints using the topology file export or from constraint manager as 'dcf' file ( some constraints will give error as they are not supported in downrev version so you make have to redo manually)
 
things to remember
- if you have any user defined subclass in 16.x you need to create them, also stackup details also need to be created  in 15.x before importing subdrawing
- text block settings should match in both design
 
As there is no direct support from Cadence for conversion I use this as workaround.
Few issues you will face while doing this downrev but can be solved looking into the errors case by case.
 
Good luck!!
~Nagaraj.
 

Thanksyou very much Nagaraj i will try and let you know.
 
Regards
 
Shakir