scandef file
Hi,
As you have mentioned, SCANDEF has Scan chain connectivity information , which is also present in netlist.
That make SCANDEF an optional one. Some of EDA tools, lets us auto- trace the scan chains ( without annotating with SCANDEF) , given the information on SCAN in/out points.
However, there are additional information present in SCANDEF file, which makes it the easier way of mapping or annotating scan chains. For example, in case , when there are multi-input components in the scan chain, tracing scan chain becomes difficult. Also it is not possible to define PARTITION information about scan chains. ( Scan Flops can be swapped across chains with same PARTITION).
These advantage of using SCANDEF, makes it preferred over auto tracing of the scan chains.
Hope this helps!!!
Daman