SCAN DEF file

1. A scandef file is a definition file that has a set of scan-specific constructs which describes scan chain information.
2. A stub chain definition describes a portion of a scan chain that can be reordered within itself. It consists of a START and STOP points, and one or more scan elements between them. These START& STOP points specify the stub chain boundaries. They can be a variety of scan chain constructs such as scan I/O ports, lockup latches, codec logic gates.
3. There is no neccessary to match the number of stub chains defined in the SCAN DEF file with the number of scan chains in the design.
4. An ordered section describes a group of scan cells that cannot be reordered within that group but can be reordered as a group within the scan cells.
5. A floating section is a list of unordered cells that can be reordered freely by the layout tool.
6. Common causes of ORDERED sections are shift registers.
7. A PARTITION name indicates that the stub chain elements can be repartitioned with those of another stub chain within the same partition name.
8. A SCANDEF file does not necessarily contain all scan cells in the design. It contains information only about the scan cells in the design that can be reordered or repartitioned.
9. Scan cells or scan segments that cannot be optimized are omitted from the file.

Writing out the SCANDEF

• write_scan_def -output<filename.scandef>
• read_def filename.scandef (command used in layout tools to read in place and route).