scan reordering and scan stitching

[jayTudu]

Hi frnds,

This post is regarding the difference between the scan reordering and scan stitching. I came across the book "The VLSI test principle..." by Xioqing Wen et al. where they have defined the Scan stitching methodology as the final connection between the scan cells, the out put of one scan cell is connected with the input of another scan cell. This is fine. But, I got little confused with the term scan reordering. The scan reordering as they have defined is the reordering of the scan cells based on the physical location of cells, meaning, the placement of scan cells will be changed. However, I have understood that the scan reordering is just to mean the reconnection of scan cells based on the reordering criteria. No need to chage the placement of cells. Although its just a matter of terminology some time its confusing also.

If any one you are working in this area please give your thought. You can refer the book by Xioqing Wen and papers by Patrick Girard on scan reordering.

Joyfully,
Jaynarayan.

 

[RaphyDu]

Generally the initial scan chain connection is in alphabetic order or by clock domain. After detail placement, the flops connected by Q->SI may be far away with each other. This may introduce some routing congestion. Scan reordering is to reorder to sequence of Q->SI conection within the same scan chain. It's not to change the placement of cells, but to re-order the chain based on cell placement.

 

[jayTudu]

Thanks Raphy for your reply. I too understood the same as you explained.

Thanks,
Jay

 

[jayTudu]

Hello frnds,
Do any one have idea about the clock rate at which the shift operation is performed in scan testing. I need proper references. If you have kindly give me the title of paper.

PreThanks,
JaY

 

[ramkka]

scan reorder doesn't change the cells placement but it will reconnect the Q-> SI pins according to the reorder.